bobinyelm
Texas
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I just came back from a 7 week trip w/ my Dometic RM3663 (3-way, 2-door w/ auto functions) equipped RV and I had the following problem:
On A/C: Unit works perfectly-nice and cold
On DC: Barely cools (though draws LOTS of amps)
On GAS: Unit lights fine, then often goes out within 2-5 minutes. Sometimes the "Check" light illuminates; sometimes it doesn't (but I can verify that the flame has extinguished).
When lit, the flame is GOOD blue flame completely enveloping the thermocouple (about 3/4"-1" high). The thermocouple produces 35mv when hot to the circuit board (verified with a digital meter).
The solenoid will click off while I am watching it, and up to the "click" I have that good flame and 35mv, so it is NOT that the flame goes out first causing the gas shut-off.
The problem appeared to start when I had one of my propane tanks re-filled, but now it is the same on the "old" (not refilled) bottle as well as the newly re-filled bottle.
I have purged the lines, and all of the other propane appliances work perfectly.
I have tried various relights (probably 20 over a few-week period), so I am sure the air is OUT of the lines.
If I unplug the 12v gas solenoid from the control board, then reconnect it, the solenoid clicks and the burner lights immediately (then often clicks off after 2-5 minutes, shutting the flame off despite a good flame and 35mv at the board from the thermocouple).
I have bypassed the control board and fed 12v to the solenoid and the flame burns continuously, though the fridge doesn't appear to get cold (though I've only done this for 30 min since if the flame were to go out, I could accumulate a dangerous amount of gas that could possibly explode if ignited).
I found this old, closed thread, but it dead-ended:
http://www.rv.net/forums/index.cfm/fuseaction/thread/tid/22969041.cfm
Anyone hazard a guess if a new board (A Dinosaur P-711) would likey fix this, or does it sound like another problem (like a bad gas solenoid)?
Thanks,
Bob
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Rob's
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The cause is the circuit board. In fact, the circuit boards on these models are somewhat notorious for having a problem with the thermocouple circuit, resulting in an erratic check light problem. We have been replacing these boards with an after market board, the Dinosaur brand with very good success. It has a 3 year warranty and a special thermocouple circuit.
Rob
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Road Runners
Tampa Bay, Florida
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It is not necessarily the circuit board. Sometimes it is the ignitor/sensor probe. I have had this problem before and I fixed it by replacing the ignitor/sensor probe.
What happens is when you turn your frig to propane the propane solenoid opens up and the ignitor/sensor starts sparking and the burner lights and burns good. Then after a minute or so the computer asked the ignitor/sensor if it is hot. If the sensor says, "Yes I'm hot" the computer tells the solenoid to stay open. But... If the ignitor/sensor sends a signal that the burner is cold the computer shuts the solenoid down and, walla, the flame goes out because there is no fuel to burn.
'05' F-250 Power Stroke
'00' 30' Cameo Fifth Wheel
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bobinyelm
Texas
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Road Runners wrote:It is not necessarily the circuit board. Sometimes it is the ignitor/sensor probe. I have had this problem before and I fixed it by replacing the ignitor/sensor probe.
What happens is when you turn your frig to propane the propane solenoid opens up and the ignitor/sensor starts sparking and the burner lights and burns good. Then after a minute or so the computer asked the ignitor/sensor if it is hot. If the sensor says, "Yes I'm hot" the computer tells the solenoid to stay open. But... If the ignitor/sensor sends a signal that the burner is cold the computer shuts the solenoid down and, walla, the flame goes out because there is no fuel to burn.
"Igniter/Sensor"
What part is the "sensor" you mention? Are you describing the thermocouple, which is the small probe that sticks directly into the flame, and has a wire that plugs into the control board? Or is this sensor another component different from the thermocouple?
If it's the thermocouple, then I did check it, and it is producing 35mv when the flame is burning. Somewhere I read that 30mv or above is normal for "hot" and anything below 15mv tells the board to shut the gas off.
Also, while I am asking, I was wondering if there is just that ONE control board visible behind the outside main vent panel that controls EVERYTHING (AC/DC/GAS power selection, gas control, temp control, gas re-ignite), or if there are separate ones hidden out of sight that control the other functions individually, such as re-light spark, or that controls the interior temperature of the fridge?
Thanks,
Bob
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Road Runners
Tampa Bay, Florida
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The probe that sparks and lights the propane is also the heat sensor. My ignitor/sensor also looked good, but I didn't want to change out the computer board so I first opted to replace just the ignitor/probe assembly. And... after I replaced it everything worked. Go figure.
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dougrainer
Carrolton, Texas
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Road Runners wrote:The probe that sparks and lights the propane is also the heat sensor. My ignitor/sensor also looked good, but I didn't want to change out the computer board so I first opted to replace just the ignitor/probe assembly. And... after I replaced it everything worked. Go figure.
He has a REAL thermocoupler on this model. It does NOT use the Spark Electrode for the flame sense. IF the flame stays lit for more than 45 seconds and then goes out in that 1 to 5 minutes, even tho the Mv appears to be correct---replace the Thermocoupler FIRST, then the control board. Doug
There is NO hidden board. You do have the REIGNITOR which is next to the control board. That reignitor is the "coil" to spark the spark electrode.
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bobinyelm
Texas
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dougrainer wrote:IF the flame stays lit for more than 45 seconds and then goes out in that 1 to 5 minutes, even tho the Mv appears to be correct---replace the Thermocoupler FIRST, then the control board. Doug
There is NO hidden board. You do have the REIGNITOR which is next to the control board. That reignitor is the "coil" to spark the spark electrode.
1) OK, just so I understand, even though the thermocouple is putting out the correct 35mv, I should probably replace it first, before the main board-the Dinosaur P-711- (I guess because it's cheaper)?
Then the message is that measuring the voltage output really isn't "testing" the thermocouple in a realistic way (the way the control board needs to see it) and it could be bad anyway?
OK, I see a small black box next to the control board.
2) I guess since the flame ignites the gas when the fridge is turned on that the re-igniter box is OK, and it is probably NOT the source of my problem?
Bob
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never_be_rich
Illiniois
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Have you tried a good contact cleaner such as Caig Lab DeoxIt? It can be hard to find. A little corrosion will really screw things up. I troubleshot mind to the point were it was a board replacement. I shot the contacts and fuse holders with DeOxit and it has worked ever since.
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Rob's
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If you read your orignal post
"I have bypassed the control board and fed 12v to the solenoid and the flame burns continuously, though the fridge doesn't appear to get cold (though I've only done this for 30 min since if the flame were to go out, I could accumulate a dangerous amount of gas that could possibly explode if ignited)."
That tells me its the board.....It takes longer than 30 min to cool down an RV Refrigerator
* This post was
edited 08/01/10 07:00pm by Rob's *
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dougrainer
Carrolton, Texas
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Rob's wrote:If you read your orignal post
"I have bypassed the control board and fed 12v to the solenoid and the flame burns continuously, though the fridge doesn't appear to get cold (though I've only done this for 30 min since if the flame were to go out, I could accumulate a dangerous amount of gas that could possibly explode if ignited)."
That tell me its the board.....It takes longer than 30 min to cool down an RV Refrigerator
Rob, think again about your logic on this. When you LIGHT the burner and you have run 12 volts direct to the Gas solenoid, NOTHING will allow the flame to go out. The reason I suggest the R&R of the Thermocoupler is twofold. 1. It IS cheaper 2. I have had Thermocouplers over the years that you can "wiggle" the wires at the Thermocoupler and make it fail. Doug
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