Fridge trouble

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prv

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The fridge on Ariam refused to play when we were preparing for the Scuttlebutt Cruise last weekend. With power to the input terminals on the compressor (checked with multimeter), there was no sign of life from either compressor or control unit.

As far as I can tell, the fridge system is this one: http://www.elyboatchandlers.com/cooling-units/isotherm-asu-3201-cooling-kit or a very close relation.

I think the batteries we inherited are fairly knackered, so it's possible they have been below a cut-off voltage some of the time, but during the trip we were plugged in two out of three nights and of course also running the engine twice a day with its hefty 120 amp alternator. Still no apparent activity from the fridge - in which I include movement in the compressor, coolness of the plate, or lights on the controller.

There's a standard automotive fuse holder separate from the compressor (obviously ok given second sentence above) and no obvious fuse in the unit itself.

Any thoughts on diagnosis?

Cheers,

Pete
 
You need to check that you are getting power to the unit. Doesn't sound as if you are. Probably a corroded terminal.

The controller should have a diagnostic LED. Search for the manual ..... It's probably a Danfoss BD35 or BD50 compressor and controller ..... possibly re-labled by Isotherm or whoever. The diagnostic light should tell you all you need to know. If it doesn't light, you have no power getting to your unit or the LED is crook.
 
You need to check that you are getting power to the unit. Doesn't sound as if you are. Probably a corroded terminal.

The controller should have a diagnostic LED. Search for the manual ..... It's probably a Danfoss BD35 or BD50 compressor and controller ..... possibly re-labled by Isotherm or whoever. The diagnostic light should tell you all you need to know. If it doesn't light, you have no power getting to your unit or the LED is crook.
 
Are you measuring >11 volts on the actual terminals (spades) not the push-on lucars - and is the thermostat telling the fridge to get on with it at the time?
I think from memory, that if you remove the thermostat connections, it should try to achieve absolute zero, so if doing that kicks it up you know where the problem lies.
You can also try to wake it up with two batteries in series, as these compressors run at 24v when on their mains adaptors. I assume it is fan-cooled, does the fan move at all?
 
Billjratt said:
Are you measuring >11 volts on the actual terminals (spades) not the push-on lucars and is the thermostat telling the fridge to get on with it at the time?
Click to expand...

I was looking at it hanging upside down through a hatch at about midnight, trying to get ready for the Scuttlebutt Cruise the next day. So not a comprehensive diagnostic session :). My (analogue) multimeter stupidly has a 10-volt range and then a 50-volt range, so to measure around 12v you have to be on the higher setting where small differences are harder to read (especially when you have both hands holding the probes and a torch in your mouth trying to see the scale!). So I'm not certain exactly what voltage I was reading, just that it was somewhere around 12v. The batteries should have been on charge at the time. I think I had one probe on the wire-end terminal and one touching the actual spade - but the connectors didn't look obviously corroded so I doubt there was much difference.

At the time I didn't know how the controller worked (I do now) so was flicking the switch backward and forward and winding the dial up and down. But either way, with the box at room temperature and the batteries on charge, it should have been trying to chill.

Billjratt said:
I think from memory, that if you remove the thermostat connections, it should try to achieve absolute zero, so if doing that kicks it up you know where the problem lies.
Click to expand...

The manual I've seen didn't say much about connections - am I right in thinking that the thermostat is the upper RJ11, above the power terminals? The cables are tucked away and not easy to trace.

Billjratt said:
I assume it is fan-cooled, does the fan move at all?
Click to expand...

Yes, it's fan cooled - no, the fan is not moving.

nigelmercier said:
You can't normally get to the compressor input, do you mean the control unit?
Click to expand...

Nope, I mean the compressor. Why would I not be able to get to the power input? It's just a pair of spade terminals.

Pete
 
nigelmercier said:
I'm only thinking of Danfoss units. They have the control unit mounted on the side, and a 3-pin plug with (230V ?) AC on it for the compressor.
Click to expand...

Seems a complete red herring to this thread, but to be clear, when I say "the compressor" I mean the whole unit mounted in a locker that takes in 12v and puts out coldness (stop twitching, physicists :) ). By "control unit", I mean the box on the galley bulkhead with the lights and switches, and by "plate" I mean the bit inside the fridge that gets cold.

Pete
 
prv said:
Seems a complete red herring to this thread, but to be clear, when I say "the compressor" I mean the whole unit mounted in a locker that takes in 12v and puts out coldness...
Click to expand...

Here is a bigger image:

3201.jpg


The control box is the rectangular bit on the left with a red face that is not covered by the evaporator, the compressor is the domed thing that it is mounted on. You can't easily get to the compressor input, as I said above.

Manual here: http://www.indelwebastomarineusa.com/Download_area/graphics/17_Download_Area_Manual_ASU3201.pdf with fault finding on Page 10.

If you can find out which terminals the thermostat goes to, bypass it to test.
 
Last edited:
nigelmercier said:
Try connecting terminals C and T on the control box, this will bypass the thermostat.
Click to expand...

Can't - that may be a compressor, but it's not my compressor :)

Billjratt seems to have a better handle on the unit I have.

I have spades for power input, RJ11 for what I think is the thermostat, and another plug (possibly RJ11 or RJ45) for the controller.

Pete
 
When I had nearly dud batteries, my fridge compressor failed to start. I put on the shore power charger and it would start. I decided the compressor must need a big starting current surge and was not having it supplied by the batteries. However, the unit did not run for much more than a year after that. It then refused to start at all and I had to replace it.
 
My Danfoss BD50 (now defunct :( ) had a 15A blade fuse fitted in an obscure position on the inverter. As Nigel has said the compressor itself is 230v Ac and has a built-in inverter.

I have had problems with a poor -ve connection to my fridge that seemed OK off-load, but caused excess voltage drop on-load and it cut out.
 
prv said:
I have spades for power input, RJ11 for what I think is the thermostat, and another plug (possibly RJ11 or RJ45) for the controller.

Pete
Click to expand...

RJ series connectors don't figure in any compressor I've met, so it's not a Waeco which has a vertical row of spades on the left hand side. The compressor and back end of the controller (attached to compressor pump) will be Danfoss or a Chinese Danfoss copy though, and probably still 12/24 volt DC in. The user control (for want of a better word) in the cabin, can be simply a thermostat or may have extra indicators for deep charging a holding plate, battery condition, error etc. I think a picture or two to help us identify the unit and put an end to the current conjecture.
I assume the battery supply goes to the pump controller which then feeds the user control, so it's reasonable for the LEDs to be dead if the power to the compressor is faulty - or the compressor is...
http://marine.dometicgroup.com/en/products/cooling_units_488.php shows a picture of a waeco with the contacts down the left - two are used for the fan, the rest are free in the pic.
Perhaps the bit with the RJ interfaces is an add-on to a standard unit?
Sorry, I've ground to a halt!
 
Billjratt said:
I think a picture or two to help us identify the unit and put an end to the current conjecture.
Click to expand...

?

I posted a link to a picture, model number, and manual in the very first post. I thought you'd read that, as everything you said up till now seemed to apply :)

Nigel has found and posted a bigger picture.

Pete
 
nigelmercier said:
It's got a holding plate!
Click to expand...

Yep!

From reading the manual, it seems to be a pretty good system, that shouldn't make too big a demand on the batteries as long as the engine (or shore power) gets used from time to time. Actually my main worry is everything getting frozen solid :)

Pete
 
These small hermetic compressors sometimes have a thermal cut out next to the compressor terminals, and may have a reset button or require a light tap to reset the bimetallic strip.

If you can get to the terminals of the comp itself might be worth applying power (presuming 12v) direct at the terminals. If it is a 240v from an inverter then I would not try this but would check the continuity through the winding first. In this case you may have three terminals with a run capacitor to the start terminal. If it is a single phase CSR (capacitor start & run) Try this link to a guide that explains how these work and how to check them out

http://www.axlr8demo.co.uk/thermagroup/documents/Issue2.pdf
 
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