12v/240v CoolMatic MDC 65 fridge not working.

[Gritineye]

As title, 2003 fridge in camper van stopped working, shows error code 5 (thermal cut out of electronic unit) meaning the ambient temp is too high for it to run. It wasn't hot when the fault occurred when switching it on, it just didn't run.

Any one have experience of this type of problem, it looks like quite a simple machine, there must be a fix, but goolgling hasn't helped at all.

Yes it's connected up wrong but all the electrics on the camper are of the same slap happy quality. I had been charging and swapping batteries a few days before, with the fridge turned off, but without removing the fridge fuse, but then I never have done in the past, so not sure if that's relevant.

A few pics.

 

[hotponyshoes]

It might well be the ambient thermal Cutout.
I lost one a couple of weeks ago, that was a 32c bimetallic type thing.
Fridge was not in use at the time of the heat wave but I think the sensor tripped and as it was the first time it had probably ever done it it might have had some corrosion to stop it resetting.
Tested open circuit on a meter so just bridged it out and it works fine again.
Cheap and easy to replace with a generic part (that I haven't ordered yet!!)

 

[Gritineye]

Thanks hps, I'm guessing that might be this ally heatsink type thing, with the two small blue things attached to the wires.

The fault showed up last May, so not very hot then.

 

[hotponyshoes]

Possibly.
Does not look like the one on mine although mine just has the cut-out. No error reporting.
I'm wondering if that one has one normally closed side, a common, and a normally open?
The closed-common makes the fridge run, if it trips out then the common to normally open gives the error code?
Looking at the photo it looks more like a mofset with possibly a couple of caps across the legs?

I'm not good with electronics though so wait for somebody else to ID that part before poking about at it.

Mine looked like this:
It was measuring open circuit and bridging across it got the fridge firing up again.

 

[Chippie]

Grit in eye, what’s the number(s) on the black thing mounted on the ally heat sink?
the 2 blue things are probably capacitors….(electronics is my bag… )

 

[EBME2]

5v linear voltage regulator for the logic board? Part numbers would confirm as above.

 

[Gritineye]

Grit in eye, what’s the number(s) on the black thing mounted on the ally heat sink?
the 2 blue things are probably capacitors….(electronics is my bag… )

5v linear voltage regulator for the logic board? Part numbers would confirm as above.

Thanks both.

The numbers are almost unreadable, don't want to disturb the thing unnecessarily so I'll take a pic with my better camera.

 

[Gritineye]

Thanks both.

The numbers are almost unreadable, don't want to disturb the thing unnecessarily so I'll take a pic with my better camera.

It took a while, but by using the grandkids toy digital microscope and a lot of photo manipulation managed to get this image of whatever the thing is.

Readable numbers look like 78120V
WC00AN302
MOR........CO

moulded in at the bottom ARC

 

[Neilj]

7812 is a 12v regulator, the blue things will be small capacitors. For a thermal cut out you'll be looking for something mechanical looking like hotponyshoes's pic above.

 

[Gritineye]

Dug a little further, these two wires go in here, red comes from the 12v regulator, the black goes to the manual on/off rotary thermostat switch.

They don't come out into this pocket behind a perforated stainless cover as you would expect,

But go up into the insulation, if this is any sort of thermal device it's inside the insulation, beyond me how it would work in there! This looks entirely wrong as if it was just shoved in there from the back without taking the inside cover off. I can't pull the wires back down or out.

The hard wire from the putty is the temp sensor from the freezer coil thingy, it goes to what looks like a brass bellows on the thermostat

Took the cover of the control board in case there was a bi-metalic cutout in there but I can't find one anywhere.

That's all I have on this one, but oddly when I reconnected the power the error code light is no longer flashing but the fridge still doesn't work...

 

[Neilj]

In that last pic there are three black wires coming off the top left of the board, where do they go to? All external wiring is via spade connectors, so I suspect the black wires go to something up inside that back plastic cover, can you get a pic of that? I had a read of the manual, error code 5 (thermal cut out of electronic unit) suggests the electronic unit has overheated so I would think the temperature sensor (whatever it is) is in there somewhere rather than in the fridge casing.

 

[Gritineye]

In that last pic there are three black wires coming off the top left of the board, where do they go to? All external wiring is via spade connectors, so I suspect the black wires go to something up inside that back plastic cover, can you get a pic of that? I had a read of the manual, error code 5 (thermal cut out of electronic unit) suggests the electronic unit has overheated so I would think the temperature sensor (whatever it is) is in there somewhere rather than in the fridge casing.

I too read the error code to mean something electronic overheating, that's why I took the cover of the PCB to have a peek in there for scorching, can't see any though.
Whatever stopped it running and triggered the fault code should have stopped the overheating becoming terminal.

Those three black wires go to a 3 pin connector on the compressor housing, hidden by the plastic cover.

I agree the thing inside the insulation is unlikely to be the problem but I just would like to know what it is to eliminate it.

 

[Neilj]

Have you got a multimeter or can you rig up a test lamp of some sort to check if you have 12 volts in various places around the wiring? That might help trace where the supply voltage is getting / not getting to?

 

[Gritineye]

Have you got a multimeter or can you rig up a test lamp of some sort to check if you have 12 volts in various places around the wiring? That might help trace where the supply voltage is getting / not getting to?

That is my aim today, the side door of the van will be open for an easy high level ejection of the whole ****** thing if isn't working by end of day!

 

[Neilj]

Dug a little further, these two wires go in here, red comes from the 12v regulator, the black goes to the manual on/off rotary thermostat switch.

View attachment 361911

What I'm thinking with this is, if this is indeed some sort of cut out buried in the insulation for some reason, then the two wires may well be connected in series with the 12v supply. With you saying the red wire comes from the 7812 and the black wire goes off to the temperature control then this could make sense. Can you measure the voltage at the three pins on the 7812 for a start? From your Post #3 pic, left pin on the 7812 is input (battery) voltage, centre is negative (0v) and right is the output, which should be 12 volts. You may have to peel that black sleeving back slightly to get to the pins but if you see those sort of numbers then at least your 7812 is ok. Next would be the black wire exiting the housing and going to the temperature control, if my thinking is correct and this is after the cut out device then there should also be 12 volts on this wire.