Fridge blue light special

[DaveSchwartz]

My white-LED replacement also didn't have this big resistor.

LAC stands for 'Low Ambient Control'. Unlike a fridge in a residence, an RV fridge may be operated where the exterior is not at 'room temperature'. The LAC feature is designed to compensate for this low ambient temperature and keep the fridge cooling properly.

I'm not sure what the purpose of adding 8 watts of heat was (or under what circumstances the control board would have energized it) but obviously they thought it could be cost-reduced out (and a ceramic wire-wound would have cost way more than a nickel).

Its part 'U' just about in the center of the following circuit diagram of the Dometic DMR-702.

[andymil]

Thanks Dave, that's the same wiring diagram as mine.

If the resistor is near the temperature sensor it may make the fridge run longer and keep the freezer cold when the room temp is low.

I bought a refrigerator last winter for the garage and had to return it because the freezer wouldn't get cold enough at 40 degrees ambient.
I bought one that was "garage ready". It has a heater built in to fool it into running longer.

[raspivey]

I'm going to have to go look at mine in the next few weeks. I've got a really noisy fan that's going to have to go in favor of a quieter computer case fan or two. My biggest concern is 12V draw while boondocking for three or four nights. I'm going to install a switch for the fans should I need to disable them...temp should be in the 40 - 70 degree range, so I'm not sure how often or if they'll even run. I'm mostly concerned about the heaters.

[DaveSchwartz]

If the fan is noisy, you certainly have reason to replace it with something quieter but in the temps you are expecting, they should not run... there is a thermostat in-line with the fan (in the schematic I posted). I've only heard mine running in 80+ conditions.

[raspivey]

I'd noticed that about the thermostat. It's been so hot here that it's run constantly and I've only had it about two months, so I haven't seen it operate with cooler temps yet. It does appear to be speed controlled with temp. The fan is noisy enough it can be heard on the opposite end of the trailer with the door closed when it's running at high speed.

I've just got to get into it and see how much of a pain it'll be to disable the heaters temporarily if I need to.

[raspivey]

Originally Posted by andymil

There is also a "LAC Heater" on the print, but the wire colors don't match anything I see. I think this is the ceramic resistor, but I'm not sure what it's for. The other lead of the resistor goes to pin 3 of the four pin plug on the light CB. It's marked LAC on the CB.

Originally Posted by andymil

Yeah, I just talked to Dometic and they told me that the resistor was not used on that model (DMR702) and it will work fine without it. Just wanted to be sure.

Just looking over the diagram and the PCB, am I interpreting this correctly as this model doesn't use the LAC?

[andymil]

Originally Posted by raspivey

Just looking over the diagram and the PCB, am I interpreting this correctly as this model doesn't use the LAC?

Yeah, that's pretty much what Dometic told me.