1991 t-1550

mclamp · 02-28-2011, 04:51 PM

I was having some trouble with my refrigerator this summer, it would only run about 20 degrees cooler than the air temp, in the fall it will freeze things, in july its running low 60's. Any one had a similar issue?
-Patrick

no job · 02-28-2011, 06:11 PM

sounds like the thermostat may be bad and also when you use lp gas or electric is
it the same temp???
no job.

mclamp · 02-28-2011, 06:36 PM

Same on gas and elec... I was also thinking thermostat, is that a DIY job?

**JohnB** · 02-28-2011, 09:57 PM

Hi Mclamp

I'm assuming your fridge is a Dometic, is it? And do you have a model/serial number? I can look it up to make sure it works like the newer ones so I do not tell you something that you do not even have....

The thermostat was mentioned. I'm going out on a limb on this not knowing what you have but most of the standard model RV fridges do not have a thermostat per say like one may think of for a furnace. They do have a thermistor that changes resistance value with temperature. The temperature control is non settable. The thermistor goes into the PC control board that then runs both the gas and electric element control. If you think this is an issue, by placing the thermistor is a glass of ice water for several minutes should change the resistance to around 8,000 to 10,000 ohms if I recall right. Have to look that number up again but you would need an ohm meter to measure it. If the thermistor stops working in an open circuit type of mode then some of the fridges go into super cool mode and will not stop cooling and you end up freezing things. It's safe to say in your case it is not failed open at least.

Now what may be causing the lack of cooling you are seeing?

These units need good ventilation up thru the back of the unit or they do not work well. They work on about nothing more then natural draft of hot air rising. Since you have a 1991 unit here are some thoughts.

Is the roof vent clogged up with dirt on the screen up on the roof? If you a use flash light and a mirror you can maybe can look up from down at the bottom where the side of the camper vent panel is looking up to see that screen. And you may only see the coil way up top, the condenser. You should be able to see sunlight for sure unless the roof screen is really clogged up. I looked up mine this way last year so I know it work. You may have to take the roof cap off and clean the screen if it really bad or has some kind of nest from insects or other things up there. Heavy dirt on the condenser coils would be an issue too.

The next area is more complex but can be an issue as the heat will not rise correctly. There is a burner stack vent or flue. This is the tube where the gas flame and heat sort of rise up thru. In the stack is a thin baffle that is on a helix, twisted piece of metal on a spiral. The height of the flue baffle is said to be important and also that a bunch of rust or soot has not clogged up the helix flue and then the heat does not rise up right. I have heard, not seen, that the flue baffle can drop down so if you do go in there make sure it is hooked up at the top and not dropped down.

Actually listed in the Dometic fridge instructions that flue tube is suppose to be cleaned annually. And it is buried in the stack. I do not know if many people ever clean that flue every year, or if ever. I myself have not cleaned mine yet but may soon. But mine is only ~ 7 years old, not 19 years or so like yours. I do compressed air blow out the bottom of the unit in the spring and check the burner.

I have taken my son's PU fridge apart when he bought it (used 89 unit) and it was loaded with mud dauber bees dirt. That little unit was easy to get to no like buried in a TT.

See here for some info on the flue baffle cleaning.

Cleaning the 'flue' on my Dometic standard fridge - iRV2 Forums

RV Refrigerator Efficiency 101 - RV UNIVERSITY

RV.Net Open Roads Forum: Dometic 7030 Fridge- Clean Flue? rust falling, poor cooling!

Is the camper level? The older units that have a square flue pipe above the burner in place of a round pipe have issues if the fridge was not level. I do not know what year those changes occurred.

It sounds like your unit is working at some level just not very cold. What was the temp inside after an overnight run on the unit?

Does it make ice in the freezer?

The easiest thing to check is the roof vent for blocked air flow. Then the flue baffle area.

There is a possibility that the ammonia flow in the cooling unit is plugged up. I myself have never been into that yet. Only read about it when rust get's in side the unit.

Hope this helps and good luck.

John

Do you have an ohm meter/volt meter and familiar with using them?

mclamp · 03-01-2011, 07:16 AM

Wow, thats a lot of information, thank you. Give me a couple days to find answers to all your questions and I will post them. Thanks again!
Patrick

OhhWell · 03-01-2011, 10:52 AM

When you say that it freezes things in the winter are you refering to the freezer or are you saying that the entire fridge freezes things in the winter?

mclamp · 03-01-2011, 11:01 AM

Im sorry, that wasnt clear. If I have the temp set as low as it will go it will freeze in the fridge in the fall or spring. But, later in the summer when its 80 out, I can have the fridge set as low as it will go and it will only run about 55 -65 inside the fridge.

OhhWell · 03-01-2011, 11:04 AM

Ahh, that sounds like the thermistor or controll board then as I would think if it was an efficiency problem, it would work better in the fall for sure but still turn down before freezing the fridge compartment.

That's not to say cleaning out everything John listed wouldn't be a bad idea. That's also not to say that my logic couldn't be flawed heheh.

-Pat

**JohnB** · 03-01-2011, 07:46 PM

Quote:

Originally Posted by mclamp

Wow, thats a lot of information, thank you. Give me a couple days to find answers to all your questions and I will post them. Thanks again!
Patrick

HI Patrick,

Thanks. well hope it helps. We too learn from you so report back whenever you get this sorted out. And what it is not...

I see you now have a sig pic.

if you need help trouble shooting, pictures really go a long way helping explain what it is you have and what your up against.

Good luck

John

mclamp · 03-02-2011, 02:38 PM

I did some looking today.

Model:

http://www.sunlineclub.com/forums/me...icture983.html

http://www.sunlineclub.com/forums/me...icture985.html

It looks like everything is clean up through the roof vent.
http://www.sunlineclub.com/forums/me...icture984.html

Is the thermostat beneath the white cover?
http://www.sunlineclub.com/forums/me...icture986.html

I dont recall the exact temps is was running this summer but like I said, about 20 -30 degrees cooler than outside temps.

I dont have an ohm meter but I believe my dad does.

Would the flu stack only matter for LP mode? It acts the same on LP and Elec.

The camper is level when we are camping and when parked, I do run the fridge on gas while hauling, the camper is not perfectly level at that time.

**JohnB** · 03-02-2011, 07:01 PM

Patrick

Pictures really help.....

Yours is a lot older then I thought. Skip the thermistor check, yours does not have it. I thought you had the electronic controls, you have the older manual control system that uses the gas valve and a capillary tube thermostat.

Here is the operators manual on the RM2301

http://dl.owneriq.net/a/a546e360-ee2...d58508bfab.pdf

I found this which may help

Dometic Manual Refrigerator Controls

I have not been into one of these older units. After seeing this is one of the older mostly mechanical units, it "might" be the actual capillary T stat OR the gas valve unit self. In this case I would lean towards the capillary T stat first as it seems to cool to the same place and then stops.

See this site. A good place as I have used this a lot before for service manuals

Service Documents

There manual on there may help

http://bryantrv.com/docs2/docs/Mandiag.pdf

Hope this helps

John

PS under that white cover is the gas valve/controller that runs the entire show

Jim-Bev-2363 · 03-02-2011, 07:12 PM

I would double check the fins at the top of the opening, just under the screen, to make sure no insulation or other junk has accumulated in the fins. Might be worth removing the top cover and screen to reach down to clean the fins. Also might install a fan to pull more outside air across the cooling fins. These things might not be your problem but they will not hurt and the cost is minimal.

jim

mclamp · 03-02-2011, 07:30 PM

Alright, thanks guys! I will probably wait until the snow melts before I get into it more but I will keep you updated.

mclamp · 03-02-2011, 07:35 PM

You might think this is a funny time to tell you this but, I do have an original 3-ring binder from the dealer with all the manuals and paper work that originally came with the camper when it was purchased new. It just happens to have a service manual for the refrigerator, would that be helpful at all?

Jim-Bev-2363 · 03-02-2011, 08:15 PM

**JohnB** · 03-02-2011, 09:08 PM

Quote:

Originally Posted by mclamp

It just happens to have a service manual for the refrigerator, would that be helpful at all?

Ahhhh yup!!!

Good luck and let us know how you make out when the snow melts.

John

Jim-Bev-2363 · 03-03-2011, 07:32 AM

I took a picture of the back of my fridge, looking up toward the top vent. Notice the coil and how you can see through the fins on the coil? It might have been the position of your camera but it could also be trash on top of the coil and that will limit the heat transfer.

You can also barely see the exhaust fan above the coil. I have a manual switch inside the camper to turn the fan on when it is really hot outside for extra heat transfer help.

Hope this helps once the snow has melted.

jim

mclamp · 03-03-2011, 07:38 AM

Ill take a look, I like the idea of starting with the exhaust fan and an interior circulating fan as a cheap place to start.

Jim-Bev-2363 · 03-03-2011, 09:37 AM

The interior circulating fan that was shown in the video runs from drycell batteries. I'll be installing a small fan that was used in a computer to cool the main chip. They are 12V and draw anywhere from a tenth to a quarter of a Amp from the house system. Friends I know do it that way, with a shutdown switch, and have no problems. Also, the larger pancake fans in computers can be used in the back flu and they are much quieter than the store brand fans that are like the small exhaust fan in the bathroom vent. Swap them out and get quiet.

After the snow melts, LOL!

mclamp · 03-03-2011, 02:53 PM

Im loving these ideas, I went out and checked the fins today... low and behold there was quite a bit of insulation laying on top, it looked like it came from on top of the fridge between it and the frame the fridge sits in. I think this will help. I am optimistic its not the thermostat 1: because this model may not have one 2. it sounds like it usually gets stuck open or close causing no cooling or supercooling. Mine kind of cools. Anyway, here are a couple more pics from today.

Before:

After:

Back Panel: