New Issue with Hydroflame Furnace 8531-III

[RandyJ55]

I'll have to practice. When I clicked on the icon for photo, the link was required instead of just attaching the photos like I would in a text message.

[Tinstaafl]

It's not you, Randy. Something (hopefully temporary) has broken the feature that allows direct image uploads here. I just tried it, and got the same result.

For the moment, the only way to insert an image is with a link to a web URL.

[JohnB]

Hi Randy,

You are welcome. Glad to help as I can.

A few comments in blue.

Originally Posted by RandyJ55

I'm reluctant to get to the limit switch but I did take the 2 white wires, one connects to the circuit board and the other to the sail switch, and I ran a continuity test and I do have continuity but I don't know what else to test for.

On the limit switch, your bench test for continuity is a good one. The switch is normally closed and opens when the heat exchanger (combustion chamber) gets to its high limit. It will close back up when the cools down approx. 70 deg F, from where it tripped out, as measured at the outside of the heat exchanger.

I have tested the hi-limit switch to make sure it opens and closes the way it is supposed to, but I had to have the furnace running in order to do the test to create the high heat in a controlled test. I was looking to make sure the switch actually opened, which takes heat and the right amount. Technically a bench test with a heat gun could do this too, but may not be as precise as the operational test.

There is a test you can do when the furnace is running, but it also will include the sail switch at the same time. The hi-limit and the sail switch are wired in series, and either can cause the test I am going to talk about shortly to show one of them opened up and broke the circuit and shut down the gas & ignition. You will not know which; odds are, the sail switch is the one that opened the circuit, but a flaky hi-limit switch can also. For now, we can assume your hi-limits switch is working.

Originally Posted by RandyJ55

I did get a new Dometic heat only thermostat, the correct electrode set and I have a new sail switch coming as well as a blower motor and a new plastic blower wheel attachment as the old one had a broken piece where it is retained on the left side of the furnace and the replacement motor I put in September ended up being the wrong one as it was 1/2 too long and the cover had to be shifted to the left to accommodate.

OK, something here is a maybe issue. The sail switch and the 8500 series rev III, and older can have different sail switches for different models and fan blades during the pre-rev IV furnaces. By the time Rev IV came, all the sail switches were to be the same.

If you were using a different motor length and maybe speed, plus the fan wheel had issues, that "might" affect the sail switch operation. The amount of wind being blown may have shifted and made the old sail switch open prematurely. You have to have enough wind blowing, which comes from motor speed, and the blower wheel is effective enough to handle the normal fluctuations of motor voltage and speed. Point: If the sail switch flutters and opens up for any reason, it will shut down the gas and ignition.

Before you took the furnace apart this last time, did you do any of these voltage tests I was talking about here? https://www.sunlineclub.com/forums/f...tml#post159391

Since you have the right new motor coming, the fan blade, and the right sail switch for your model, the hope is the motor and sail switch will work as they should. If you put everything back together and the gas burner and ignition shut down instantly again, then we need those voltage test data I spoke to, and we can do a new test to make sure the sail switch or the hi-limit switch is not opening up, shutting you down.

The test is that you put the volt meter onto the white wire going to the PC board from the high limit switch and DC ground and see if the voltage drops out when the burner and ignition come on. This is a furnace running test. You will have to get a thin needle of sorts to get the volt meter probe into the white PC board connector, but that test will prove if the sail switch/ hi-limit switch safety circuit is shutting down the gas valve and the ignition.

See here, the white wire going onto the PC board, you need to test that wire for loosing power.


Make sure the new sail switch paddle size and the switch closing action are the same as the original switch. That relationship has to match.

Originally Posted by RandyJ55

Once the new motor and cage comes in next Tuesday, I can begin reassembly. I expect the sail switch in tomorrow or Saturday. It's pretty much bare bones now with everything out but the limit switch.

Please let me know if I can perform any other test on the limit switch remotely, if possible.

See the above info on the limit switch and sail switch

Potentially,the only things I didn't change was the valve assembly and the limit switch for this 8531-III furnace.

To your other question:

Originally Posted by RandyJ55

John, I have one more question. I had to bend the tab for the igniter wire because when it arrives, both tabs for the wires to connect to are straight and will jam straight into the gas valve assembly as is and the wires not the high tension boot won't go on.

I got the igniter electrode assembly mounted and the burner head screwed to the valve assembly, but is the

ground prong in the middle supposed to contact the burner head

or should I elongate the holes to adjust it till it clears or simply try to bend it clear of contact? I should have taken some pictures when I extracted the unit so I would have as many questions. Let me know your thoughts. Thanks John]

The wire boot issue, yes I can see that is a problem. It is not going to go on straight in from what I can see.

To the ground pin of the electrodes touching the screen, I would say no, something is not right. I have never seen the ground pin touch the screen on the Rev IV furnaces.

This video you told us about, has some pics showing the ground electrode does not touch the screen, there is clearance there. See these and check that the screen setup is in the right spot.

https://youtu.be/xSliED1d48A?si=Vo9XvHrRoWS7hIxA

Scroll the video to the time marks:

20:50 shows some good views

21:03 shows some clearance between the ground pin and the screen. It is only there for one second of the video.

27.02 shows a side view with a good amount of clearance with the screen area.

Are you sure you bought the correct screen? Something is not lining up right with the screen and probes.

Hope this helps and good luck.

John

[JohnB]

Originally Posted by RandyJ55

I'll have to practice. When I clicked on the icon for photo, the link was required instead of just attaching the photos like I would in a text message.

Lets see if we can "attach" a pic

The attach feature seems to work. Not sure about the linking feature.

[JohnB]

Originally Posted by RandyJ55

I'll have to practice. When I clicked on the icon for photo, the link was required instead of just attaching the photos like I would in a text message.

Until the photo icon issue is sorted out, use the Attach feature for pics. You can attach four pics at the end of each reply. If you need more than 4 pics, do a second reply.

Please look at this post I linked on how to attach and upload pics. I do this off a PC; I am unsure how the phones do it. And if there is an Apple or Android things difference

https://www.sunlineclub.com/forums/f...tml#post159374

[JohnB]

Originally Posted by RandyJ55

I'll have to practice. When I clicked on the icon for photo, the link was required instead of just attaching the photos like I would in a text message.

OK, maybe you are doing something wrong.

Here is the postage stamp icon liking in a hi-limit switch from my Flickr account

testing the postage stamp link



It works as of this post. Maybe you are doing the phone linking incorrectly. This is off a PC when I did it.

[JohnB]

Randy,

If you haven't yet, when you have the gas burner out, unscrew the brass gas jet out of the gas valve, hold it to the light, and look through the hole for anything clogging it. Please don't poke at it; soak it to clean, as any scratch you put in the jet can mess up the flow pattern. You can use alcohol or other high flash cleaner.

[RandyJ55]

Hi John, The last component is coming in today for my 8531-III furnace. That is the plastic squirrel cage. I have all of the other components but need to know if that successful continuity test on the white wires validates the condition of the limit switch which is more disassembly if it's not good. I see where the wires lead to but the motor housing section is in the way and the process looks ominous. For a matter of the remote sense electrode, the manual calls for and I've installed 36999 with the bent prong being the igniter and the straight prong being the flame sensor. I still would like to know if the ground prong is supposed to be touching the burner head assembly at any point. Once I can confirm all of this, I can begin reassembly. Even if you sent me a link to a video explanation regarding the limit switch and the ground prong, I would greatly appreciate it. Thank you very much for your input of knowledge and experience in assisting me in resolving this issue. Just a note. A site called Young Farts for RV Parts sells many of these RV furnace parts including Atwood furnaces that I've seen listed as low as 250 on up .

[RandyJ55]

John, I was able to get clearance between the ground prong and the screen as you recommended. I believe a series of issues lead to the erratic behavior of my 8531-III furnace. Reverse wiring in the igniter, the wrong motor installed, a burnt thermostat at the screw and the anticipator and a broken screen. This scenarios leads to collosal failure. Even the wheel set screw and end piece on the left side of the squirrel cage was broke free with no retaining the cage. I will perform the running hi limit test once I get the furnace running. I hope to start reassembly by Monday, weather permitting. Thanks John

[JohnB]

Hi Randy,

It appears you are making some headway.

I did not hear how you sorted out the new burner head. From the older service manuals, your 8531-III uses a 32811 burner head. Did you find that 32811 head?

See here in blue from your prior post

Originally Posted by RandyJ55

Hi John, Thanks for your input. I found that the old burner head was broken and the dual sense electrode and surrounding metal was blacked by burner head issues. I also noticed that the dual sense electrodes were over 3/8 away from the burner head and the prongs spread more that 1/8 apart. I need to know which part of the electrode the orange and black wire attach to because I ordered and received a new burner head and cleaned up the electrodes and reset the spacing while at the same time i ordered a new #37517 dual sense electrode which will be here in 2 days. I want to do a test run with the gas off and capped to see if the old electrode at least sparks when it is supposed to after the fan and time delay sequence clicks to green light the ignition. I believe that the orange wire goes on the bigger part of the electrode but I'm not sure. I appreciate any feedback for clarification. Thank you.

I'm hoping you may have found a real 32811 burner head, did you? Or did you get a 30286 head?

It appears the 32811 has fallen into the discontinued parts saga of the Dometic takeover of Atwood.

This afternoon, I ran into this post with really good pics of the original 32811 and how the one-member TT_VRT solved his by robbing parts of the 30286 to add to his old 32811 so the screen would work right.
https://www.irv2.com/forums/f258/atw...em-596201.html

Those pics clearly show how the ground electrode misses the screen when the 32811 is used. It is yet to be determined if using the 30286 will spread the flame correctly. And if you are using the 30286, that may explain why the ground probe was hitting.

On the hi-limit switch, unless you have the furnace out of the camper on a bench test, I'm not sure how you will test the hi-limit for pure temperature tripping when it gets too hot. Please look here if you'd like to see how I tested mine. https://www.sunlineclub.com/forums/f...tml#post155058

Since your hi temp switch tests are closed for continuity, that can be about all you can test for short of the full-blown temp test under controlled conditions. In the RV shops, I "assume" if they suspect the hi-temp switch is bad, they will just plan to replace it and move in; it would cost them more labor to run the heat test then to just install a new switch.

You have a lot of issues at the moment, the hi-limit may not be one of them. The odds are low the switch is bad. Once the furnace is running, you "might" be able to hear it trip off and then back on. It will all depend on how the heat ducts are routed in the camper and their size and quantity. If the heat ducts are wide open and enough of them for the 31,000 BTU-sized furnace, that high-temperature switch may never trip as there is enough air going through the heating chamber to cool the amount of BTU's coming from the gas burner. That said, not all campers are setup to allow this the hi limit will never trip.

If there were never enough wide open ducts or they had a few too many bends from the factory, partly crushed ducts, etc, then as the furnace runs, you can hear the gas burner drop out, the fan keeps running, and then the burner kicks back on once the heat chamber cooled off a little. The Hi limit will cycle the gas burner this way, and you may have never known it unless you know how the furnace works. If the camper is cold and you are 10 plus degrees away from the setpoint on the T stat, then the system will run a long time to catch up. You might hear the gas burner cycle on and off a few times before the T stat is satisfied.

Good luck, and I hope this all comes out OK for you. You are gaining.

John

[RandyJ55]

Hi John, I got everything put back together, I do have close to 13 volts coming into the furnace area from the coach. The high limit still has continuity when not in use. My brother touched the red and white wire and just the fan comes on no click or ignition. The fan cycles and then shuts off. I took the circuit board to Meyers RV supercenter and they tested the board and it passed. Now I have to see where the issue lies. It's either the sail switch or the TDR. I am going to manually close the sail switch when the two thermostat wires are out together as I have left it outside of the cover for this test. If there is still no click, I will try another sail switch. I really needed to know if there is a way to bench test the TDR using a 12volt source to see if the one I has failed or is ok. From this point, I'm not sure where to look because if the sail switch, TDR, and circuit board are good, I'm not not sure where else to look. I will have a better idea once I run the sail switch test tonight. I do suspect the TDR at this point but I have 8 of them including the one I just purchased and I need to figure out which ones are shot. Thanks John for your input

[RandyJ55]

Hi John, I wanted to give you this important update. My brother got home and we did the test with the external sail switch while I held it so it made contact after the fan started and the furnace ignited. After I got the circuit board tested I used another part of the harness to get a new section of wire going to the sail switch ,from the sail switch to a different tdr. When my brother got home we ran a test and then I let it go from a heat to a cool cycle and then the furnace shut down. I then installed the new thermostat on the wall and so far the furnace is working as designed. I told my brother to let me know later when the furnace does a complete heat and cooling cycle so that we can make sure it stays functional. So tonight will be the first test and I will then tie wrap the wires and double check connections and call it good. Thanks for all your help and insight in helping me resolve this issue. I know my brother is glad .

[JohnB]

Hi Randy,

It appears you have the furnace operating like it is supposed to. GREAT news! Good for you.

There are ways to test the TDR on the bench. There are also ways to test the TDR installed on the furnace, along with testing the sail switch and hi-limit switch together in the furnace in the event it comes to be. Just ask; it is a combo of the tests I mentioned above with a volt meter in the correct place.

Hope the heat keeps working tonight!

John

[RandyJ55]

Hi John, It's 10/28 and the furnace ran for 3 days with no issues but it rained last night and today my brother comes over and informs me that the furnace lights for 10 seconds and blows cold air and keeps trying to cycle. I'm at a loss after all the work and parts. I haven't even had a chance to check the limit switch while running. I will go out and check the connections to make sure all is good and possibly after dark to see if anything sparks, etc. I may need to use a propane back up source in the event that I have to do an extensive disassembly so that he will have heat. He lives on my property in an RV and has a 100 gallon tank filled, so I need a safe reliable alternative in case of a major issue. I know you probably have a better idea than myself. I will continue to troubleshoot to see if moisture was an issue or if there is definitely a limit switch issue. With the multitude of parts and time , I hope to resolve this issue before winter settles in for good. Thanks for all you've helped me with so far. I will review, recheck and try to find the issue.

[JohnB]

Hi Randy,

Lets see what we can find.

Originally Posted by RandyJ55

Hi John, It's 10/28 and the furnace ran for 3 days with no issues but it rained last night and today my brother comes over and informs me that the furnace lights for 10 seconds and blows cold air and keeps trying to cycle. I'm at a loss after all the work and parts. I haven't even had a chance to check the limit switch while running.

I will go out and check the connections to make sure all is good and possibly after dark to see if anything sparks, etc.

Need more info on the statement in blue. This much I am following, but not what happens next.

The furnace has worked for 3 days correctly.

After a rainy day, then:

The furnace lights and burns for 10 seconds. OK, Understood.

When the burner stops, yes, that vintage furnace will keep running blowing cold air until you either shut off the T stat or the T stat has reached its set point.

Here is where we need more info.

You stated, "keeps trying to cycle." Need to know what cycle means, and does it keep repeating non-stop? Please expand on what it keeps trying to do. And did it do something 2 times, 3 times etc.

Here are a few things to help tell what is or is not the problem; this checking may help turn up something.

Try and take pics of your furnace and post so I can see what you have. This is the closest 8500 series rev III I can talk to to show you what you have to check from. This does not have the remote flame sense set up like yours; it is a local flame sense.


Look at the white wire going to the white connector on the PC board. That white wire, when it is live with 12 VDC power, is a run signal to the PC board to start the ignition. The white wire is the return path of power starting at the TDR, through the sail switch, and the hi-limit switch IF both are closed. See if you can get a thin needle or probe to get a voltmeter onto the white wire on the back side of the connector (the same side the wire goes in) so the PC board will still work and you can check the voltage on that wire. That white wire will be pos. + 12 VDC when a start ignition signal is needed. The voltmeter will read the signal while the furnace is running. And go to 0 volts when there is no signal.

With the furnace running in this mode where it just blows cold air non-stop and the gas burner is not burning, OR the ignition is not snapping, check if that white wire has 12.7 or higher volts DC in relation to DC common (-). If it does, then you know the PC board is being told to turn on the gas and ignition. If it does not see 12.7 or higher DC volts, then the PC board is not being told to turn on the gas and ignition, and the problem is with the
power source at the TDR, the sail switch, or the hi-limit switch as a start.

The above is a key piece of info on where to start the hunt, is the PC board being told to start the Gas and Ignition sequence?

Yes, check for loose connections.

Do you know the part number of the PC board you have installed? I know you have it checked and it passed the RV dealers test, but it would be good to know what board your furnace has as the features kept advancing as time went on with fault logic in them and when the furnace stops on safety for ignition failures.

Also, try this: when the system acts up, have you tried to shut off the furnace, and then turn it back on, and what does it do? Pay close attention if it tries to light three times and then stops trying to light again. The same thing goes for after the "first" 10 seconds burn when it shuts the burner off. Did it try three more times trying to light and then stop?

I lost track of if you bought a new PC board, I know you had it checked, but pending what you come back with after doing some checks, you may have an intermitting working PC board. But we need more info before we can get to that assumption that the board is intermittent.

Hope this helps

John

[RandyJ55]

Hi John ; The PC board 31501 is the board that I purchased and installed in 2021. I was wondering if you could outline the procedure for bench testing the TDR so I can rule out this component as the issue before moving onto something else. I did retest and confirm continuity with the limit switch wire into the PC board and the other end where it connects to the sail switch when not in operation. I need to mention that this furnace is getting about 13.67 volts. The RV is plugged into shore power but does get a charged battery to use when there is a power outage. It seems strange that 3 days after flawless operation that it would suddenly fail to ignite or sense a flame after 10 seconds. Once the TDR is verified as good, I can continue to search for another issue. I will check to see if the furnace tries to light 3 times then shuts off or continues. I hope to get you some feedback on the areas you wanted me to check tomorrow. I did go out and attempted to test the furnace and it would not stay lit for more than 10 seconds.

[JohnB]

Hi Randy

Originally Posted by RandyJ55

Hi John ; The PC board 31501 is the board that I purchased and installed in 2021. I was wondering if you could outline the procedure for bench testing the TDR so I can rule out this component as the issue before moving onto something else.

I did retest and confirm continuity with the limit switch wire into the PC board and the other end where it connects to the sail switch when not in operation. I need to mention that this furnace is getting about 13.67 volts. The RV is plugged into shore power but does get a charged battery to use when there is a power outage. It seems strange that 3 days after flawless operation that it would suddenly fail to ignite or sense a flame after 10 seconds. Once the TDR is verified as good, I can continue to search for another issue. I will check to see if the furnace tries to light 3 times then shuts off or continues. I hope to get you some feedback on the areas you wanted me to check tomorrow. I did go out and attempted to test the furnace and it would not stay lit for more than 10 seconds.

On The TDR, I'm assuming, by your prior message, that you are using the Dinosaur TDR, yes/no?. This one. https://www.dinosaurelectronics.com/TDR.htm

If you want to do a bench test, you will need a 12-volt battery and, ideally, a 12-volt DC incandescent (LED will work, too, maybe) light bulb on a pigtail socket. I’m unsure if that relay uses dry contact or an SCR type output, but a 12-volt bulb of any size will work. I cannot find a wiring diagram or a pin diagram for the TDR relay on the Dinosaur website or open web to tell you what pin is on the back of the relay. There should be a cut sheet that comes with the TDR to tell what each pin/terminal is. If you need help sorting this out, post a picture of the cut sheet.

The basics are this of the TDR pin out:
A- 12 VDC supply battery negative (-) goes on the TDR Negative terminal.
B- 12 VDC supply battery positive (+) goes on the TDR Positive terminal.
C- The light bulb is used as a load, which will mimic the motor blower. One side of the light bulb goes on the blower (load) terminal. The other side of the light bulb goes to the battery-negative terminal.
D- Use a hot 12-volt jumper wire off the battery (+) terminal and touch it to the TDR coil or input terminal. This terminal is the same one the T stat wires attach to in the furnace. When you put live 12 volts on that coil/input terminal, then after 4 seconds, the light bulb should turn on and stay on constant as long as the 12 VDC power is applied to that terminal. When you remove the input/coil wire, the light bulb will stay on for 2 minutes as an Off delay to mimic the cool-down period of the blower after the T stat signal went away.

I know you asked how to bench-test the TDR; the above is how to bench-test it, but, that TDR will be tested in the furnace. If the blower runs when the T stat calls for heat, the TDR works. And when the T stat stops calling for heat, after 2 minutes, the blower should stop. If that happens, the TDR is working and not the problem. You said your brother stated the blower kept on running; if it was running, the TDR is working. And if the T stat is turned off and the blower times out, the TDR is working. The gas burner and ignition not working is something else other than the TDR.

OK, you said you bought the 31501 PC board about two years ago. I'm not sure where you bought it, there are many places, and here are 2 of them.

https://www.amazon.com/Atwood-31501-.../dp/B077YVWT8L

https://www.rvupgradestore.com/Atwoo...-p/41-1505.htm

That new style PC board has onboard diagnostics, an LED that blinks to tell the fault, and has the three times trail for ignition sequence, upon starting to light, or loss of flame, and the gas system lock-out feature. You must turn the furnace off to reset the fault while in lockout. The LED will blink to tell what happened to cause the lockout.

Please take a look at this sticker for the blinking codes. This is off an 8500 series Rev IV furnace that uses the same PC board.

Your older furnace may not have that sticker, as the feature may not have existed back then. Again, posting pics of what you have helps us tell better what you have. See what blinking code yours is sending when the furnace stops burning. If there is no code, the sail switch, high limit switch, or a wiring connection issue is not sending the run signal to the PC board to start the trial for the ignition sequence.

Hope this helps

John

[RandyJ55]

Hi John, Strange turn of events. When starting the furnace for the first time, no clicks, the fan kept running. I shut down the furnace and put a new end on the thermostat wire connected to the TDR and also reversed the wires connected to the sail switch so that the blue wire is on the bottom and the white wire is on the upper connecting prong and the furnace lit, ran for 5 minutes then the heat shut off, restarted and did that intermittently and the light on the PC board flashed once a few times and the furnace relit and when it did stop heating there was no flash button then it relit again . I guess the temperature in the RV was 57 and my brother set the thermostat to 70 so the furnace had to keep igniting to warm the RV up. I'm still waiting to find out if the furnace completed one full cycle and shut off. I'm somewhat bewildered by the erratic behavior of the furnace . I plan on doing the running voltage test for the limit switch but with temps in the 30s, I'm hoping to keep the furnace heating as long as possible. I just got told that furnace did go into the cool down cycle so I'm hoping that the furnace can stay operational. I'll keep you posted.

[JohnB]

Originally Posted by RandyJ55

snip...

I shut down the furnace and put a new end on the thermostat wire connected to the TDR and also reversed the wires connected to the sail switch so that the blue wire is on the bottom and the white wire is on the upper connecting prong and the furnace lit, ran for 5 minutes then the heat shut off, restarted and did that intermittently and the light on the PC board flashed once a few times and the furnace relit and when it did stop heating there was no flash button then it relit again . I guess the temperature in the RV was 57 and my brother set the thermostat to 70 so the furnace had to keep igniting to warm the RV up. I'm still waiting to find out if the furnace completed one full cycle and shut off.

Hi Randy,

Reversing the wire connections on the sail switch would not affect the operation of the switch, but it could scrape off any corrosion in a connector and then make it work.

When the LED on the PC board starts to flash, you have to focus on it and count the number of blinks in a pattern to tell what code it is sending. The pattern will repeat if the PC board is locked out in a fault. There would be a pause between the next pattern string to blink.

If the camper was 57 and the T stat was 70, then the fan should run the entire time. But, the gas burner may cycle on and off until the temp in the camper satisfies the T stat. Once the T stat is satisfied, the burner stops, and the blower runs for the time-out cycle to cool down and shits off.

The gas burner can cycle on and off due to the hi-limit switch. If the heat chamber gets too hot, the burner shuts down and restarts on its own when it has cooled enough. On a really long heat-up, like 57 to 70 F, the burner may cycle many times. Check the heat ducts for a crushed or blocked hose or heat vent. If all hoses and vents check out OK, then the system "might" be working as it will due to the sizing of the furnace and the small number of heat ducts to get all the heat out of the chamber in time before the heating chamber reaches the hi-limit switch.

The "only" way the gas burner will run all the time (non-stop) from a very cold start to a normal inside temp is "normally" from one of two events. I'm sure there may be other events to cause this also, these are what come to mind quickly.

1. The BTU sizing of the furnace is lower than the capacity of the blower and ductwork to cool the heating chamber before the hi-limit switch trips.

2. The hi-limit switch has failed in a closed position.

No. 1 above gets messed up on campers and cycles the burner on and off due to the ductwork restrictions or initial sizing. Technically, if all is made and working perfectly, the hi-limit switch will never trip as the air flowing through the furnace is greater than the heat being created, and it keeps the furnace cool enough not to trip the hi-limit switch.

No 2. I have never found a failed stuck on the hi-limit switch. I'm sure it may happen, and an RV tech doing this for 40 years, I'm sure, has seen something like this.

It is somewhat common that the hi-limit systems will cycle on and off with a long-run cycle in a camper. This is not only a Sunline brand issue; the other brands have it as bad or worse due to sloppy duct routing and installation.

Just explaining this in case the above is what you see, which can seem erratic.

Hope this helps

John

[RandyJ55]

Hi John, I just wanted to let you know that it's been 2 days and the furnace is running fine. I believe that changing the end of the thermostat wire that connects to the TDR was at fault as there was no click on the prior try. My brother claims that the furnace seems to run quiet and has no problems. I believe that the erratic behavior was because of the contrast between the set point of the thermostat and a room temperature of 57. Once the furnace was able to cycle both heat and cool, the furnace seemed to normalize. I've tested 5 different TDRs that I have, and all bench tested good. The real test will be upcoming when winter sets in. I will keep you posted in the event the furnace continues to run well or if something else happens. Thank you for your ideas, knowledge, and guidance throughout this process.