Not sure what your skillset is or if you can use a meter. I don’t know anything about the unit. That said, a stuck relay would be evident if you could disconnect the thermostat connection that feeds it. Or simply check the output of the thermostat at different temperatures.
is this a manual or electronic thermostat? I am guessing that is what is failing. A sticky relay or contractor is possible as well, but without a schematic I am guessing.
Thanks for this, appreciate the response a lot.
I can use a meter for simple stuff, but my skillset does not include much compressor experience. ( though I consider myself fairly capable of researching possibilities and performing basic diagnostics)
I opened the unit today today, and had a quick look. The controller / circuit board looks fine - looks brand new actually, no dust or obvious moisture effects. Capacitors all look ok and soldering looks ok. I gave it a squirt of contact cleaner anyway.
I think the thermostat is electronic, and that it is working ok - the display indicates when the unit its trying to engage the chiller and when it is trying to engage an external heater - these lights turn on off as expected (ie the chiller light goes off when the temp drops to the set point) and the temperatures involved match manual readings, so I'm concluding the thermostat is functional. I will check thermostat input voltages tomorrow.
The compressor continues to run when the display indicates it is not running not supposed to be running. Also there is no delay after powering up the unit before the compressor starts, which there used to be (it used to take about 3 minuties before the compressor would start up) , making me think a sticky relay is to blame. The unit previously made a loud 'clunk' as the compressor turns off, which hasn't happened since it failed, ( even when turning off the power) which I think also suggests a sticky relay. I did hear the faint click today as a setpoint temperature was reached, which did not lead to the compressor turning off either - I presume this was a relay input.
Unfortunately it seems the compressor starter / relay / overload protector models are no longer available, so I will need to do a bit of research to find appropriate replacements, but my plan is to replace these and see how things go. The fan was a bit sticky - and I might replace that too.
Thanks for the links to the service manuals - I hadn't found these online, and learnt how to open the unit the long way.
Cheers
P
