Furnace issue

dryflie · 04-24-2018, 07:20 PM

I've got a Hydro Flame 8500-111 furnace in my 96 Solaris. Blower works great but no ignition. My PC Board has tested OK with a signal to the ignitor. I naturally suspect the ignitor as the problem but wanted to get some confirmation. Could it be a gas valve issue? would the ignitor fire in the absence of gas?

Thanks for any advice you might offer.

Al

**JohnB** · 04-24-2018, 09:10 PM

Hi Al,

I looked up the 8500-III series furnace. This older vintage still has a timing relay in it. By the time the 8500-IV came they did away with the timing really and put that blower purge timing feature on the PC board.

Need a little more info to help better. You said

Quote:

My PC Board has tested OK with a signal to the ignitor.

Tell me how the PC board was tested that a signal was going to the igniter? That will be a key piece of info depending on how the test was done. If the PC board is sending an igniter signal, that would rule out sail switch and the hi temp switch safety circuits. I'll wait for your response to help better on this.

To your other 2 questions:

Quote:

I naturally suspect the ignitor as the problem but wanted to get some confirmation. Could it be a gas valve issue? would the ignitor fire in the absence of gas?

If the igniter is actually being told by the PC board to start firing off, the same signal goes to the gas valve by the PC board. So yes, the igniter will fire regardless if the gas valve opened or not.

But... tell us about what you hear. Listen real close, may have to go outside and listen, if the igniter is actually sparking you should hear a low snapping like the electrodes sparking. If you listen close enough without the blower noise so loud in your ear,. you can hear the sparking. If you cannot hear it at all, it may not be firing off.

But, if it is not firing, then the gas valve still can operate but will soon go out on safety with no flame sense. Another thing to listen for is the "clunk" of the gas valve opening. That and the smell of raw LP gas rotten egg stink out of the outside blower vent. Have someone inside start the furnace with you outside. Once the blower starts, about 15 to 17 seconds of air purging happens. Once timed out, then the gas valve should open (goes clunk) and the igniter starts sparking. If you do not hear either 1 clunk of the gas valve opening or the sparking of the ignitor then the PC board is not sending the signal and we need to dig deeper into why. And tell us if you smell raw LP gas outside.

Let us know what you hear or do not hear and smell?

Do you have a volt/ohm meter and know how to use one? We may need to get into a more advanced troubleshooting effort pending your answers.

Hope this helps

John

mainah · 04-25-2018, 08:37 AM

If the igniter has power it does not necessary mean it will work. It's a fairly high failure part. When you turn up the thermostat it starts a prepurg and sets the timer once the timer cycles it allows the gas valve to open and starts the firing cycle. As John said listen for the sounds the gas valve is pretty obvious the igniter not so much. If it's an original board it will only try once to fire then give up then just blow cold air until you cycle the thermostat. The igniter if it's working can give you a pretty good jolt so be careful working around it so no I don't recommend grabbing the wire to see if it's working! Some furnaces had a little window you could actually see a spark.

dryflie · 04-25-2018, 06:49 PM

John, thanks for the reply. Lots of good questions. As to the PCB I pulled it and took it to an RV service shop. Guy took it out back and returned with the news that it had tested Ok, it was sending an ignition signal. Now as far as various noises. There are none, I know what the ignition click sounds like as I've dealt with the Fridge for years, it's got a sticky valve and often needs to be hand lit. So no ignition click for sure. As for the gas valve I can't say I've heard anything. I've hit the on/off switch at the furnace, topped out the T-stat, and sat outside to click the On/off switch on. Nothing but cold air from the exhaust. No gas smell. So perhaps the Board is faulty?? I will certainly get it retested. Hope this is helpful.

dryflie · 04-25-2018, 06:52 PM

Maineah. Thanks for your reply. Where are you located in Maine?? This trailer giving me an issue is parked up on the banks of the West Branch of the Penobscot out on the Golden Road.

mainah · 04-26-2018, 05:35 AM

Quote:

Originally Posted by dryflie

Maineah. Thanks for your reply. Where are you located in Maine?? This trailer giving me an issue is parked up on the banks of the West Branch of the Penobscot out on the Golden Road.

I'm just south of Fryeburg. Yeah I know the Golden road have friends with a camp near Northeast Carry.

mainah · 04-26-2018, 06:09 AM

Quote:

Originally Posted by dryflie

John, thanks for the reply. Lots of good questions. As to the PCB I pulled it and took it to an RV service shop. Guy took it out back and returned with the news that it had tested Ok, it was sending an ignition signal. Now as far as various noises. There are none, I know what the ignition click sounds like as I've dealt with the Fridge for years, it's got a sticky valve and often needs to be hand lit. So no ignition click for sure. As for the gas valve I can't say I've heard anything. I've hit the on/off switch at the furnace, topped out the T-stat, and sat outside to click the On/off switch on. Nothing but cold air from the exhaust. No gas smell. So perhaps the Board is faulty?? I will certainly get it retested. Hope this is helpful.

The gas valve and the igniter work at the same time,the igniter is timed meaning it only operates once in the cycle if no flame is detected that entire chain shuts down and the fan continues to run to purge any propane that maybe in the fire box. You really should hear the gas valve it's pretty loud. Most gas valves have some type of connector you can try removing it and check the voltage during the start cycle it's a pretty safe test because there will be no propane flow. The output of the igniter is pretty high voltage and I'm not sure how he tested that if the igniter has a 12 volt signal that does not mean there is high voltage output. I'm going to say your control board is toes up. Regardless of ign. the gas valve has to open or there is nothing to light. A very good upgrade to any older furnace is a modern board for a couple of reasons the new boards will try 3 times to light before it gives up some now even time out and shut the fan down (nice trick so it does not blow cold air for hours) My suggestion would be a Dinosaur board they are a very will built unit.

krazedave · 04-26-2018, 08:15 AM

I have to agree with Mainah on the board being bad even if it tests good. We had board tester in our shop and a board would test good but the furnace would not fire up. We tested every part of the unit and all was good. Installed a new board and unit fired right up. We thought our test unit was bad and called the mfg their reply was if the board tests bad it is bad and if the board tests good it still could be bad. We stopped testing boards and just put a new in and 99% of the time problem solved and yes go with a Dinosaur board.

**JohnB** · 04-27-2018, 06:07 PM

Quote:

Originally Posted by dryflie

J. So no ignition click for sure. As for the gas valve I can't say I've heard anything. I've hit the on/off switch at the furnace, topped out the T-stat, and sat outside to click the On/off switch on. Nothing but cold air from the exhaust. No gas smell. So perhaps the Board is faulty??

From krazedave it appears the board testers are not total fool proof.

If you have no gas and no spark, while not impossible, odds are low both of those systems would die at the same time unless the board is bad.

If you have a voltmeter or even a 12 volt test light you can try the gas valve for power. If no power when it is suppose to start then the board is not sending it or a loose wire connection.

The other thing to try and confirm this before buying a new board is to confirm the 2 safeties are met telling the board to start the firing/gas sequence.

There is a sail switch (in the blower housing) which is in series with a overtemp switch. I do not have 100% confirmation on the 8500-III series however the 8500-IV and the 7900 series uses a white wire on the safeties. So if you look on the PC board connector plug there should be these 3 or 4 wires in the plug connection to the PC board.

Red = gas valve power
White = the safeties signal, A series connection from the sail switch and over temp
Black = the ground (neg - 12 DC volts)

Black = A 4th could be a remote flame sense sense feedback. Yours may or may not have this.

Those wires above are on the plug strip.

There is also a igniter wire coming off the board but it connects to the ignition coil not the push on multi wire connector. Careful of that igniter wire, it will feel like a spark plug wire getting you if it is live. 10,000 volts jumps an inch so do not grab that one.

If the white wire has power going into the board, it starts the whole firing sequence. If no power then the sail switch or overtemp switch has issues or a loose wire. You can test with a 12 volt test light or a voltmeter.

Basically, If the safeties are giving the board 12 volts and the gas valve does not have power after the timeout period, odds are high your board is toast. On the 8500-III with the separate timing relay for the blower purdge, the board should fire fairly quickly after getting the safeties power.

Hope this helps and let us know how you make out.

mainah · 04-28-2018, 08:44 AM

One more thing you might check the exhaust system it is coxual not only does it expel exhaust it allows fresh air in it is possible the bees have taken up residence inside and the fan is not getting enough air all though you have said it sounds fine it may not not be enough air to close the sail switch.