Refrigerator only works on shore power?

[CaptRick]

So my trailers refrigerator stopped working while dry camping this weekend. It will only work on shore power (120V), if I switch it to propane, the pilot light fires up it runs for about 2-4 minutes and shuts down and the trouble light comes on?
I can hear the black box near the burner click when it shuts down.
I cleaned the burner tube and the igniter and there was no change. A friend suggested that there is a fuse in the black box that may be bad?
Before I take it in to a shop I figured I would post this up to see if any one else had this problem and what they did.

Thanks

[CaptRick]

Yea the terminology confused the heck out of me, I was good to go on the "thermocouple" until the "flame sensor" came into the discussion. The parts manual called it a thermocouple so thats what the problem was as far as Im concerned.....

[j-d]

Thanks for the update!

As for me, think I'll study up on Thermocouple vs. Flame Sensor...

Only time I've dealt with this was on a very old Dometic and it had a thermocouple with a screw-in connector. Since then we had a Dometic DM2852 (same as your 2652 just a little larger fridge section) then Norcold N811. I didn't have to look at the 2852 and so far not the 811.

Glad you got'er done, and for cheaper than a Control Board.

[CaptRick]

Fixed!!!!
It was the thermocouple. Got a new one in 48 hours for $ 29.00 put it in this afternoon and its back to working correctly.
Thanks for all the help:)

[CaptRick]

dougrainer wrote:
This post is WHY it is important to give year/Brand and model of appliance and RV when asking for help. There are 2 flame sensor types and both Norcold and Dometic have used both over the years.
1. Is the Thermocoupler pictured in the one post
2. Is what I call the flame sensor and is also the spark electrode. There is NO thermocoupler at all in the standard sense.
One poster talked about and had a pic of what he thought was a refer thermocoupler. Well yes, 25 to 30 years ago. The Metal tube type thermocoupler used on Dometic has 2 wires with a spade terminal on each wire and connects to the main control board. BUT, Dometic uses both types and it depends on the model number. Doug

It is a Dometic 2652 not sure of the year but the trailer is a 2000 Aljo. I went out on a limb and ordered up a thermocouple (2 wires going into a copper line)thinking that may be the issue and it only cost $ 28.00 so Im not hurt to bad if Im wrong.

Last night I took everything apart cleaned it all up, checked the fuses on the control board and the same problem persists. The flame will burn for 2-4 minutes and then there is a click and the flame shuts down. The new part should be here Thurs or Fri, I hope to get this all sorted out as I have a trip scheduled for the following weekend before I winterize until my Texas trip in Feb. Thanks for all the help.

[wa8yxm]

camperpaul wrote:
The flame detector (thermocouple) may be defective.

I support that theory, or the chip on the control board that reads the flame detector may be bad, or the wire that connects the two may have dirty connections.

On some systems (And frankly I do not know which our fridge uses) the thermocouple is a double duty device... For example on my furnace it is both the ignitiion point and the thermocouple.. This wears it out faster but.

During Ignition there is about 1,000 volts more or less on that point

During flame sense 0.480 (less than 1/2 volt)

If the change over goes wonkey that half volt detector gets hit with a kilovolt and zap, it's history.

On my furnace this happened (Or I suspect that's what happened) I repalaced the main control board with a Dinosaur board.

Dinosaur boards includes PROTECTION against just this kind of failure.

[dougrainer]

This post is WHY it is important to give year/Brand and model of appliance and RV when asking for help. There are 2 flame sensor types and both Norcold and Dometic have used both over the years.
1. Is the Thermocoupler pictured in the one post
2. Is what I call the flame sensor and is also the spark electrode. There is NO thermocoupler at all in the standard sense.
One poster talked about and had a pic of what he thought was a refer thermocoupler. Well yes, 25 to 30 years ago. The Metal tube type thermocoupler used on Dometic has 2 wires with a spade terminal on each wire and connects to the main control board. BUT, Dometic uses both types and it depends on the model number. Doug

[CaptRick]

j-d wrote:
When the furnace goes to light on LPG, the Logic Board sends power to the Gas Valve to open, and STAY OPEN long enough for the ThermoCouple (TC) to get hot. Then the board takes the power it provided away, relying on the power produced by the TC to continue to hold the valve open. No TC output, gas valve flops shut, LPG flow stops, flame goes out. Our early model Dometic (RM763) would actually cycle. You'd hear Clunk>Spark>Pop>Flame>Click>Flame Out>...Repeat...



In this picture, the connector that attaches to the gas valve is in the middle of the loop. The Loop Looks like copper tubing and the Nut Looks like a gas fitting nut. But they are NOT. The tubing is one side of an electric "cable" and the other conductor runs down the center inside some insulation. Finger tight plus maybe 1/4 turn is all it takes to make up the connection. There's no LPG there to leak, so it doesn't have to be tight. And too tight will short out the connection and the ThermoCouple won't work.

EDIT: Doug was typing while I was. Suggest going with his timing on the cycling of the gas valve. As I remember, when our old Dometic was doing that (and it turned out to be a bad TC) the cycle was less than a minute.

So from what you are describing as well as Doug it sounds like a bad thermocouple, is that the same thing as the flame sensor Doug mentioned?

Thanks

[CaptRick]

dougrainer wrote:
1. There is NO pilot light. That is the regular flame
2. Yes, it could run 2 to 4 minutes if the Thermocoupler was bad, but that is rare. MOST flame sensors shut down after 45 seconds, UNLESS you are not watching and the refer does a triple start. Most refers have a tri start ignition cycle that will light, then shut down after 45 seconds, the wait a few seconds and relight and if it shuts down will wait a few seconds and then try the 3rd time. If no flame sense after the 3rd try it locks out and the check light comes on. THAT can be your 2 to 4 minutes. IF that is not the case, then a flame thermosensor can have an intermittant operation and then shuts off randomly.
3. NO FUSE will cause this problem. It is either the Flame sensor or the main control board. 9 time out of 10 it is the flame sensor, unless you have a Dometic refer built from about 1992 to 1998. Doug

Forgive my ignorance but is the flame sensor the same thing as the thermocouple?
I cant find any part called the flame sensor in the parts catalog. My unit is not doing the 3 cycle you described, it is just burning for 2-3 minutes and then shutting down the flame.

Thanks

[j-d]

When the furnace goes to light on LPG, the Logic Board sends power to the Gas Valve to open, and STAY OPEN long enough for the ThermoCouple (TC) to get hot. Then the board takes the power it provided away, relying on the power produced by the TC to continue to hold the valve open. No TC output, gas valve flops shut, LPG flow stops, flame goes out. Our early model Dometic (RM763) would actually cycle. You'd hear Clunk>Spark>Pop>Flame>Click>Flame Out>...Repeat...



In this picture, the connector that attaches to the gas valve is in the middle of the loop. The Loop Looks like copper tubing and the Nut Looks like a gas fitting nut. But they are NOT. The tubing is one side of an electric "cable" and the other conductor runs down the center inside some insulation. Finger tight plus maybe 1/4 turn is all it takes to make up the connection. There's no LPG there to leak, so it doesn't have to be tight. And too tight will short out the connection and the ThermoCouple won't work.

EDIT: Doug was typing while I was. Suggest going with his timing on the cycling of the gas valve. As I remember, when our old Dometic was doing that (and it turned out to be a bad TC) the cycle was less than a minute.

[ScottG]

Before replacing the thremo-couple, use a brass brush to gently clean the carbon off it (the carbon insulates it from the flame). Many are replaced when this is all they really need.

[dougrainer]

1. There is NO pilot light. That is the regular flame
2. Yes, it could run 2 to 4 minutes if the Thermocoupler was bad, but that is rare. MOST flame sensors shut down after 45 seconds, UNLESS you are not watching and the refer does a triple start. Most refers have a tri start ignition cycle that will light, then shut down after 45 seconds, the wait a few seconds and relight and if it shuts down will wait a few seconds and then try the 3rd time. If no flame sense after the 3rd try it locks out and the check light comes on. THAT can be your 2 to 4 minutes. IF that is not the case, then a flame thermosensor can have an intermittant operation and then shuts off randomly.
3. NO FUSE will cause this problem. It is either the Flame sensor or the main control board. 9 time out of 10 it is the flame sensor, unless you have a Dometic refer built from about 1992 to 1998. Doug

[camperpaul]

CaptRick wrote:
If the thermocouple were bad would the pilot still light and run for 2-4 minutes?

Thanks

Yes.

[CaptRick]

Batteries and propane tanks are good. There is no air in system as the refrigerator burner starts and runs with a good blue flame for 2-4 minutes before it shuts down.
If the thermocouple were bad would the pilot still light and run for 2-4 minutes?

Thanks

[camperpaul]

The flame detector (thermocouple) may be defective.