OK So it is not the thermostat..

[Tim Lamb]

Fairly ancient Hotpoint fridge over cooling!

Replacement thermostat failed to cure. Any suggestions short of calling an engineer?

[Andy Burns]

is it the frost-free type?

[tabbypurr]

how could that happen if the stat is working as it should? Is the bulb in the right place? Sounds like it's come adrift.

NT

[Tim Lamb]

Umm RLA51P so don't think so.

Google says the thermostat probe has moved away from the proper sensing position and not fixable!

[Tim Lamb]

Yes. Apparently buried in insulation and not repairable/getatable:-(

I'll try pushing it further down tomorrow.

[tabbypurr]

Old fridges have the stat bulb on the evaporator metal plate.

NT

[Dave Liquorice]

repairable/getatable:-(

KISS, mechanical, very reliable but easy to fix if it does go wrong.

More recent (10 to 20 years...) ones have thermistors stuffed down the outside of the interior casing and under the insulation. An electronics board to measure the temp and control a triac to turn the compressor on and off. Lots to fail, designed in "faults" (thermistor getting displaced and unable access it to fix it), progress eh?

I suspect the miss placed thermistor is the reason why our old dual compressor fridge/freezer became an intermittent freezer/freezer. Oddly it's not found it's way to the dump yet, maybe I'll have a dig through the back and insulation to see whats what...

[Brian Gaff]

What does the thermostat actually control? Is there more than one thermostat, Does it perhaps operate a relay with multiple contacts? Other than that, can you actually here it starting and stopping etc? Brian

[Brian Gaff]

Sounds a bit defeatist, that. What exactly is the sensing position. If it has been made it can be unmade and fixed surely, even if it might mean making a hole somewhere and then putting a bung in it afterwards. Brian

[Tim Lamb]

In message , Brian Gaff writes

I have a can of foam on the workshop shelf:-)

I expect the problem will be knowing where to dig. The thermostat sensor tube runs across the fridge top and then, presumably, down the back.

I've not yet pulled the fridge out of its slot so don't know if the evaporator area is recognisable/reachable.

[tabbypurr]

This sounds very inaccessible but you said you replaced it. If all else fails you could put a trad thermostat onto the evaporator plate and run the microtube out under the door seal. A bit bodgey but would work correctly.

NT

[Tim Lamb]

In message , Tim Lamb writes

Progress! The fridge is out of the slot. The condenser grid is only secured by 4 screws (not warm to touch although the compressor appears to be running). Behind that is a sheet of corrugated plastic which could be cut/peeled off over firm foam insulation.

Guessing the sensor route puts the tip near the bottom of the fridge chest. I'll try poking the replacement further in before attempting anything more drastic. Big label says PENTANE.

>

[Tim Lamb]

Hmm.. We are on the point of marketing the farmhouse! There is an ambition (not mine) to abandon all the existing white goods to the new owners....

[Dave Liquorice]

I have sneaky feeling that the evaporator is outside of the inside of the fridge, buried behind the insulation. There is no evaporator plate as such in our wonky fridge/freezer, the plastic back of the fridge cabinet just gets cold.

[Mr Pounder Esquire]

If it is conventional? Is the back of the fridge all iced up?

[Tim Lamb]

Yes!

[Mr Pounder Esquire]

In that case the evaporator at the back of the fridge (could be hidden by plastic) is not getting to a low enough temperature to tell the stat to turn off. The evaporator temp should hit maybe -20C. The compressor will keep running (?) and running and this will form ice and snow on the evaporator. The fridge temp will get too low due to the amount of ice and the compressor not turning off. Put your hand on the compressor. Is it very hot? If it is and you have fitted the correct stat, sorry, the fridge is f***ed. I used to fix these things nearly 20 years ago (arggggg).

[Tim Lamb]

Likely:-(

Lots of noisy gurgling in operation. Compressor too hot to hold and condenser barely lukewarm at the top.

Oh well..

[Mr Pounder Esquire]

Yip, red hot compressor beating it's heart out trying it's best. End of days.

Don't replace with a "reconditioned" unit. All that can be done is to clean and test that it reaches temperature. They may even fit a new stat if they feel like it. Been there and done it. In my day a stat was less than 2 quid.

[Dave Liquorice]

Or the device measuring the evaporator temperature isn't doing it's job properly, either because it's bust or bad connection or isn't in proper contact with the evaporator or positioned where it should be,

Yers.

As it's running at 100% duty cycle I'd be surprised if it wasn't very hot. They aren't designed for 100% duty cycle.

As it's iced up due to the compressor not switching off, the control system is f***ed, the heat pump is working, just working to much...

I don't think Mr Lamb has given any description of what he has replaced other than "the thermostat". There has been a general assumption that "the thermostat" is a mechanical one with capillary etc. It could be an electronic one, with a thermister buried in the insulation around the back somwhere, this would fit the other descriptions of the fridge better.

Our's always made odd gurgling noises but had virtually silent compressors.

If it's been like this for a while, the heat pump will have drawn the temperature down as low as it can and the only heat it can pump out is the little bit that conducts into the cabinet. So the condensor won't be as warm as it would be if cooling down room temeparure stuff that has been placed in it. Also the fact it is so cold will buffer the effect of putting room temp stuff in it.

I thought you where going to have a dig about in the back and use some squirty foam afterwards?