Fridge trouble light

[LHaven]

The Dometic DM2852 (conventional propane/electric) fridge in my rig has developed a tic. Twice now in the past week or two I've noticed that both lights on the eyebrow are on -- Auto and Check. Turning it off and then back on clears the Check light.

My understanding (and the manual's) is that the Check light can only mean that gas ignition has failed. But I'm hooked to shore power and we haven't had any outages. If I switch auto/gas to gas, the fridge transitions fine, no Check light. If I turn it to gas mode, then off and on, the Check light appears for a half second before turning off. All this is exactly what you should expect.

According to the manual, the only time the check light should be on during AC operation is if there was a power failure, the gas failed to ignite, the Check light turned on, then the power returned. I'm positive nothing like this has been happening.

Is there some other obscure reason why this Check light would keep appearing during continuous AC operation?

 

[Larrys-5TH]

I experienced this once years ago in an Aerolite. Loose neutral on the fridge wiring was the problem, and only triggered on a windy day (presumed the shudder was enough to wiggle the wires). May be a long shot for you, but an easy check.

 

[Kirk's Outback.]

Not sure if this is your problem, but I started having abnormal issues with my Dometic fridge that was driving me crazy. I removed the switch panel to get some info from the data tag, and while I was pressing the buttons, I noticed one of the buttons catching on the bezel ever so slightly. All buttons felt good and worked fine, but if more than one button was pressed accidentally / simultaneously, they could catch, causing it to fault out. I elongated the bezel holes until I was able to replace it permanently.

 

[LHaven]

Received this from Dometic:

"A check light showing up can be from interference, DC voltage dropping below 9.6 DCV or AC ripple on the DC line. If the check light stays on and refrigerator does not work properly then it could be failure of a gas component or bad or loose ground at the lower board , gas valve or converter."

Going to clean and tighten the neutral and ground connections first, I think.

 

[LHaven]

Two nights ago we had a mild thunderstorm. Opened the fridge in the morning, there was no interior light and interior temps were rising past limits, but both eyebrow lights were on so DC to the fridge was OK. I took out all the perishables and ice and let the unit defrost because it needed it. Could not turn off check light no matter what I did.

Late yesterday, I pulled the 15A fuse, then restripped, No-Ox'ed and reconnected all DC connections from main infeed to both sides of the terminal block. Blew all of the cinders out of the propane compartment floor. Figured out how to remove the lower board cover without breaking it. Still had check light and no interior light. Turned it off and went inside to download some manuals. When I got back, I turned the fridge back on, check light went out, interior light came on. Thought maybe the No-Ox took some time to eat corrosion off the terminal block pads.

Let it run all night. Freezer temps were well under 32° by bedtime. This morning, check light on again, interior light off. (It's really handy that the interior light has been a reliable indicator of working/not working.)

Since we're operating on shore power, this isn't any of several possible propane problems. I think I'm down to cleaning ground (have to find it) and lower board replacement. Manual says it could also be a fuse problem, but fuses don't resurrect. More fun today.

 

[LHaven]

3A and 5A fuses test OK. Chassis ground cleaned and No-Oxed. Thermo/thermal fuses (in series) test OK. DC in is 13.1V. AC ripple with converter fan running is 0.18V. AC in is 116V. Thermistor well in specs in ice water. AC in tests fine but AC out to electric heater shows zero. Soaking thermistor in warm water right now to make sure it "calls." Looks like I'm down to faulty lower board or faulty upper board.

 

[LHaven]

The upper board doesn't have enough brains on it to blow its nose.
Ordered a Dinosaur lower board, if I'm lucky, should be in Fri or Sat (if not, Tue). Wish me luck.

 

[LHaven]

Dinosaur board fixed all my problems.

I especially like the added "bias" rheostat on the board that lets you adjust the gross temperature setpoint so that your "sliding thermistor" adjustment inside the fridge isn't always maxed out in one direction or the other.

After installing the board, I noticed that the usual half-second blink of the "CHECK" light every time the fridge ON switch is pressed was much shorter, almost invisible. Dinosaur tech tells me that blink is not the unit testing the propane, but is the lower and upper boards communicating with each other. Apparently the Dinosaur board is way faster about that than the stock board.

 

[NH_Bulldog]

We used a Dinosaur board when our Dometic/Atwood water heater board failed in the Passport. Very reliable and as you noted, an upgrade over the original. I don't always buy something simply because it is made in America, but doing so with RV parts has treated me very well (converter, various control boards, thermostat, soft start, inverter, etc.).