Fridge thermostat

[richardh10]

My fridge has gone on the blink, and although I think it is the thermostat,I would like to check, so is there a way to bypass the thermostat to see if it works. It is a frigoboat compressor fridge.
Thanks

 

[pvb]

Yes, look at the manual and you should be able to see where the thermostat wires are connected to the control unit.

 

[GHA]

Looks like this?

If so, connect the 'C' & 'T' terminals together on the controller - so a croc clip lead between the bottom and second one up. Existing thermostat should be plugged into those, might be easier to take them out to get at the terminals. With those 2 shorted together the fridge should run continuously.

 

[richardh10]

Thanks for that.
Assuming that it is the thermostat, would the replacement have to be a frigoboat, or would any generic thermostat do?

 

[ithet]

Thanks for that.
Assuming that it is the thermostat, would the replacement have to be a frigoboat, or would any generic thermostat do?

I broke my thermostat on a Isotherm unit that uses the same Danfoss compressor (new, while fitting it!). The actual thermostat unit inside the housing was a Ranco unit. Although the actual model number of unit was a specific type not available to buy, I replaced it with a generic Chinese copy type which worked fine when fitted in the original housing (although the zero position was different). About £5 against a proper replacement for £70, e.g.:
Typical copy thermostat

Another option is to fit an electronic thermostat.

 

[Daverw]

If you take out the thermostat you will see it’s a standard fridge stat in a small housing. Take it to your local fridge trade counter, Climate Centre, HRP etc they will have one similar for about £10, when mine failed as said above I fitted an electronic one as it also allows the box temp to be displayed, just cut a small opening in the side of the cupboard, this cost be nothing as I had one in my tool box, benefit of being a fridge engineer but you can get them for not very much of the internet, just make sure they are 12v supply and you just wire them in the the same connections, temp probe goes in the box

this is an option MH1210A DC 12V Thermostat Regulator Digital LCD Refrigerator Controller Sensor 656202025220 | eBay

 

[richardh10]

Many thanks. It is now apparent that the thermostat isn't the problem. Unfortunately I've no idea what is!
The compressor is in a hotter place than would be ideal, but I'm stuck with that. Also, it all started working for a few hours after I had turned it off, and then it stopped again.
Experience tells me this is going to be expensive!

 

[Norman_E]

Many thanks. It is now apparent that the thermostat isn't the problem. Unfortunately I've no idea what is!
The compressor is in a hotter place than would be ideal, but I'm stuck with that. Also, it all started working for a few hours after I had turned it off, and then it stopped again.
Experience tells me this is going to be expensive!

I thought the thermostat on mine was faulty, but it was proved to be low gas. Re-gassing has it up and running but with the suspicion that there is a very slow leakage, probably from the evaporator pipes which are very old aluminium ones. Another pressure test is planned for friday to check if gas is slowly leaking.

 

[Baggywrinkle]

The system will also have a low battery cut out which can be difficult to diagnose if you're not lookng for it, it's the compressor starting that trips the cut-out. Make sure the batteries are well charged and/or you are on shore power.

 

[Graham_Wright]

You will find the Penguin website very helpful for diagnosis. There is a facility built in which gives fault indications if you connect an led as directed.
Electronic Start Unit Controller BD35F, BD50F 12V 24V Danfoss SECOP Equivalent 7109532080726 | eBay
Lists a replacement controller.

 

[richardh10]

Excellent info everyone.
Thought there may be a low voltage cutout so ran the engine to make sure the batteries were fully charged, but no luck.
Have had a suspicion all along that it may be low gas, so that is the next avenue to explore. Is it possible for someone with no experience to regas or is it a job for the professionals?

 

[Daverw]

Does the compressor run all the time and still not get any cooling? If the compressor runs and then stops it could be low gas as the compressor can overheat as it uses the gas to cool itself. most small systems don’t have a low pressure switch that would stop the compressor with low gas levels.

regassing comes up all the time on here, not as easy as it gets described, for a long term solution as you really need to find out where it’s gone first, then repair and then prep for regards, if you search for many of the previous post on here you will get the info you need, but again I must stress it’s not legal in the UK or many parts of the world to actually do this, morally as well for anyone who cares about the planet we all live on.

 

[Deleted member 478]

If any part of the evaporator plate is sweating i.e. drops of water on it instead of frosting, call in a pro. They'll look for the leak, which is usually very difficult to detect. They sort the leak, then vacuum your system to get rid of any moisture, then re-gas it correctly. Re-gassing is an art best left to the pros.

 

[vas]

fwiw, try another v.easy test as well: disconnect the thin fan cables (go to the same danfoss controller somewhere in the middle just under the powersupply (iirc)
I had a fan failure and for some reason fridge wouldn't work, unplugged the fan, fridge started straight away (OK not for long with no fan... but worked!)


cheers

V.

 

[alancollins]

I have the same fridge and am replacing the thermostat ( £30 from Penguin). I put a volt meter across the wires connecting the thermostat expecting to get 12 volts or a bit more, but only found about 4. I have not yet connected the new thermostat in case I have another problem. Any suggestions?

 

[Cactus Sailing]

Many thanks. It is now apparent that the thermostat isn't the problem. Unfortunately I've no idea what is!
The compressor is in a hotter place than would be ideal, but I'm stuck with that. Also, it all started working for a few hours after I had turned it off, and then it stopped again.
Experience tells me this is going to be expensive!

if you link the thermostat (so it thinks the fridge is warm so the compressors comes on) you should hear it click in and come on even if it has no gas, it will then either cut out almost immediately (no gas) or drop out after about 3 seconds in which case it could be either of 2 faults

1) the battery voltage is just too low so it cuts out (i cant remember the actual voltage been a while since i worked on the fridge)
2) the fan at the back of the heat exchange is faulty (or internal fridge fan if fitted) and drawing too much current thus the compressor trips out and tries again on switch on/off

thermostats are about £5 off ebay for a mechanical like for like, (if its danfoss branded i think they wanted like £35-40) or you can get a fancy electronic one for about £5 too, but it will need a power supply.
if the fan is faulty like i found in mine (caked up in dust and stalling causing excessive current) then look for low current PC fans, you may also find an internal fridge fan wired into these connections too which can cause issues if its not a low current one.
you can also disconnect the fan briefly to see if the fridge comes on, if it does then you know it needs replacing.

if it is a danfoss fridge with the electronic controller you can also stick a LED on it to fault find;

at least a few things you can try ^^

 

[GHA]

I have the same fridge and am replacing the thermostat ( £30 from Penguin). I put a volt meter across the wires connecting the thermostat expecting to get 12 volts or a bit more, but only found about 4. I have not yet connected the new thermostat in case I have another problem. Any suggestions?

Sounds close, just measured my 101N0220 controller, 4.96v between the 2 thermostat terminals.

 

[PaulRainbow]

Many thanks. It is now apparent that the thermostat isn't the problem. Unfortunately I've no idea what is!
The compressor is in a hotter place than would be ideal, but I'm stuck with that. Also, it all started working for a few hours after I had turned it off, and then it stopped again.
Experience tells me this is going to be expensive!

Might be helpful if you described what's happening ?

 

[Big John]

I have the same fridge and am replacing the thermostat ( £30 from Penguin). I put a volt meter across the wires connecting the thermostat expecting to get 12 volts or a bit more, but only found about 4. I have not yet connected the new thermostat in case I have another problem. Any suggestions?

I would not expect to see 12vdc on the connection for the thermostat, you are reading a voltage from the control circuit. The thermostat switches the control circuit which in turn, turns on the compressor.

 

[alancollins]

Thank you gentlemen. I live and learn.