Danfoss fridge misbehaving

[Balbas]

Morning, our old Longbow has one of those 'convert your coolbox into a fridge' Danfoss compressors and cold plates in it. 'Great' thought I when we bought the boat, as I was only expecting a coolbox.

Unfortunately it doesn't work. It fires up, the compressor runs for 30 seconds or a minute, then it stops, waits 5 seconds and the cycle starts over again. It never gets cold.

Short of ripping it out and replacing it with a new one - which at £400 or so I'd rather avoid, as that's money I'd rather spend elsewhere on the boat - where do I start with fixing it?

 

[Ross f]

Go onto Vyv Cox website - there is good information about trouble shooting there. I nursed mine all last year by periodically re-gassing it as there was a continual leak of the refrigerant. Fitted a new Penguin compressor and cold plate (£500) in March - only took 3 or 4 hours and have had a nice cold fridge box all summer - even through the heat wave.

 

[superheat6k]

Short cycling as described suggests a control fault, 30 seconds is not long enough for the system to start any noticeable cooling at the evaporator plate, although after the compressor stops you might hear a light gurgling sound as the refrigerant flow settles.

Check if power to the compressor is cutting out on the external feeds to the compressor terminals, yes check thermostat, no check the overload klixon.

Inside the compressor terminal box is a klixon bimetallic cut out. It sounds like it is cycling on that. So either a faulty klixon or the compressor is drawing excessive current. The maximum amps or watts (amps = watts / voltage) might be stamped on the compressor somewhere, so check this first. If it is OK then try bypassing the klixon inside the terminal box, then if it works OK replace the klixon. I would not advise leaving the klixon bypassed other than for testing.

If it is excessive current then the compressor might be goosed.

I doubt your system has a low pressure cut out, but if it does then this could also cause the cycling described. If you are short of gas then search the pipe work including evaporator plate and condenser for oily patches. Just adding more gas is at best a short term solution and if done more than once is actually an offence.

 

[vas]

had some issues this summer and it turned out that the cooling fan on the matrix (or whatever you call that thing that heats up...) was drawing more than x milliamps.
Easy test, remove the + or - thin wire off the control box (just under the top two power supply red and black) and see if it fires up. IF it does, replace the fan.

Possibly something more difficult and expensive as SH points above, but worth a minute unplugging the fan and writing this option off.

good luck!

V.

 

[sailaboutvic]

You could also try and shorting out the thermostat and see what happens , if you find it keeps running ok , I would forget about replacing it with genuine one and buy a cheap 12v Chinese unit from eBay , works much better and not only you have contro what temps you run it at but at anyone time you know what the temp is in the fridge .

 

[Balbas]

Lots to think about, thanks all. Next time I'm on the boat I'll do some testing and report back.

 

[Balbas]

Searching for Danfoss fridge faults brought up not only a You-tube video explaining the diagnostics, but also a handy PDF. So... armed with a multi meter I popped down to the boat yesterday and ran through the tests. Three flashes (or beeps with a multi meter set to continuity) told me that it was either a control unit fault or a voltage (stabilisation) fault. As I'm getting good voltage to the feed, it was obviously the control unit which had failed, so I've pulled that out.

I'm hoping that the 'brand new, never been used' control box I bought for £20 on ebay fixes my problems...

 

[vas]

Searching for Danfoss fridge faults brought up not only a You-tube video explaining the diagnostics, but also a handy PDF.

http://www.veco-na.com/images/So_what_makes_you_think_your_compressor_is_bad.pdf

by any chance?

good luck although I've not heard of many control units failing. For 20quid you cannot go wrong though!

cheers

V.

 

[Balbas]

Well it seems that the £20 controller is doing the business. I now have a cold 'plate' at the back of my fridge and the compressor no longer cycles on and off - which is nice. Time will tell just how cold it gets - I suspect that really it'll only work if I fill the fridge up with stuff - but it seems to be a pleasing result so far.

 

[Walusotu]

Had exactly the same problem with my fan-cooled Danfoss unit.
Thought I had a good voltage feed but turns out it was the negative wire from my busbar to battery which only became apparent under load. Changed the wire and all is OK.