Waeco fridge compressor has died, any ideas why?

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dedwards

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I have a waeco cooling kit installed along with a 240v->12v transformer but it has completely stopped working. I'm trying to work out whats wrong with it but have run out of ideas.

No matter what I do, there is absolutely no sign of life.
I've disconnected the power terminals and measured over 13v at them (using boat batteries and shore power), i've replaced the thermostat control with a manual switch and disconnected the fan but still no life. I've also wired up an LED which supposedly gives diagnostic flashes but again no life. Assuming that the electronic module was dead I sent it off to Dometic who returned it saying theres nothing wrong with it so now i'm stumped.
the electronic module is model no 101N0200.
Any ideas what else I can try?
Is it possible to remove the compressor without specialist tools so I can test it at home/ send it off to be checked?
 
have you tried measuring the input voltage when its connected to the fridge, if it remains the same when the fridge is turned on and the module has been tested then it has to be the compressor. They do fail but its quite rare. maybe its gone past its heeling angle and come apart inside.
The compressors are still available and it can be removed with some spanners, all going well it wont leak past the self sealing couplings.

steve
 
mine went recently, £100 for new control module basically if there is power and you bridge the thermostat thats all it can be
 
I havent checked the voltage while connected to the fridge so will do that. Though I do have two separate power sources so I'm reluctant to blame that.

I am leaning towards the idea that the compressor is dead but that doesnt explain why I couldnt get the LED to light up as that is supposed to indicate compressor issues.

The only other explanation is that Dometic got it wrong about the control module being ok - but that also sounds pretty unlikely.
At least I now know I can remove the unit and get it sent off, thanks.

Any further suggestions still welcome....
 
just for info to correct an urban myth, the compressor consists of a little piston/pistons running just like an ordinary compressor, they give up the ghost because they wear out, just like an engine, heeling angles have nothing to do with it, this myth comes from the days of ammonia filled systems when if you tilted it the liquid got in the wrong place and it stopped working. To get back to the question, the compressor is probably shagged, try to bypass the controller and apply voltage direc to the compressor terminals and see if it starts.
Stu
 
Not quite the same unit, but simialr problem.

The actual compressor is run by a electrical (onic) box.

Its connected by a several wires, 12v supply, the thermostat switch, and power to the compressor.

Long way round to saying that the electrical box was U/S, and easily if not expensively replaced (160 squids)

Your unit might not be the same tho......

Weaco were fairly helpful when rung up.

Phone number is on the web somewhere.

Good luck

MJ
 
I don't believe the pump will be worn out on a boat fridge. Think about the fridge/freezer that's been in aunty Mauds house for 20 years without stopping, although it's getting noisy... Morgana's right, If I remember the pump runs on AC at some odd frequency (400cps?) Anyway, sticking a battery across it won't help. The Waeco system doesn't self-seal, so if you take it to bits, you will need to send the whole lot back to get it recharged ( unless you can source a local engineer with the vac pump etc.) If you have a "mobitronic" power supply, the battery volts go though it to the compressor (via internal relay) and become 24v when you're on shorepower. You must, therefore, measure at the push on connectors on the controller to see what's really happening (with the fridge switched on and turned up). If it has a fan, does that start? ( or the pump if it's water-cooled). (different part of the controller)
 
If the pump runs on AC, does it have a capacitor to start it? If so it could be a blown capacitor that is stopping it from running. If I remember correctly capacitor start AC motors have more starting torque than other types, and are therefore the logical choice for a motor which is directly coupled to a compressor and has to start against load. My own fridge compressors are not Waeco make, but I think both have starting capacitors.
 
OK, will try to reply to all:
Dometic (the owners of Waeco) tell me I cannot apply dc directly to the compressor so that option is not available.

The fan does not start.

The mobitronic unit delivers 24v!!??? I'm sure I measured 13v coming out of it.

because Dometic tell me that the control module is ok, i'm essentially at the point of deciding whether I need to remove the compressor or not.

I thought I had pretty conclusively eliminated the power source as the problem but if BilljRat is right about the shore power unit then I got something very wrong with the measurements.

I guess I need to go back and re-measure everything but this time while the unit is connected and turned on. What is really giving me doubts is the fact my LED isnt lighting up.
Has anybody else connected an LED to a danfoss compressor?

thanks all.
 
During the current spell of cr4ppy weather, I have been studying the Danfoss unit and the optional control unit, as mine was installed with the unit and control as it came in a kit. It is running on a 24 volt supply (which is a feature of boats with a Watermota engine of a certain age.) It has always been intolerant of low battery voltage and I have found out that this is because it is on 24 volts. On 12 volts the cut-out voltage is away down at 10.4 volts and cut-in at 11.7 but on 24 volts supp;y it cuts out at 22.8 and cuts in at 23.4. After running overnight, the battery voltage will not allow it to cut in. The control unit I have built provides for adjustment of theses tolerances and also incorporates leds to indicate power-on, fan on and the diagnostic led for reason for failure. I will fit it when the current series of atlantic lows passes over.
 
Ken,
that sounds interesting. A couple of questions:
1. Why have you included a power LED on top of the diagnostic LED? doesnt that fulfill both roles?
2. Do you know what sort of signal the control unit sends to the compressor? If I can't apply a current to the compressor, maybe I could at least put a multimeter on the connector (mine is the 3-pin type btw)
 
I did initially install it backwards but on realising my mistake I reversed it. There was no visible sign of damage to the LED from the mistake. When I get back to the boat I think i'll replace the LED with a voltmeter instead and see what I get.
 
I have put three LEDs because the one that connects between the fan +ve and F terminal does not show power on. It is the diagnostic one and flashes to tell what type of fault is present. 1 flash is batttery protection shutdown, 2 is fan overvoltage, 3 is compressor start-up fault, 4 is compressor overload, 5 is eloctronic fuse shutdown (whatever that is!). I also want one that tells me when the compressor is actually running, and the nice people at Waeco told me the simplest way to do that is from the fan + and - ve terminals. The fan negative is held at supply voltage until it comes on at which point it falls to 12 volts below supply, i.e. in my system it falls to +12 volts.

The electronic unit measures the voltage at switch-on. The system can operate on 12 or 24 volt systems without modification. If the thermostat is calling for cold, the unit then generates an ac current for the compressor at a frequency controlled by the resistance of the thermostat circuit. That threw me as I thought the T/stat was a simple switch. When I found the resistance of mine was about 700 ohms, I thought I had a problem, but this actually means that the compressor runs at 3000 rpm. Of it were zero ohms, the compressor speed would be 2000 rpm. I suspect that means that the ac frequency is 100 or 50 hertz to drive the induction motor at that speed. (I have never really got to grips with the reationship between frequenct and rotation speed and always had problems explaining to students why the 50 Hz mains caused a rotor to turn at 1500 and not 3000 rpm.)
 
Just to clarify: Your Mobitronic has two inputs - the battery or the mains. It has one output to the compressor, but the voltage supplied will be different depending on which input is dominant. Offshore, the 13.8v(!) is fed through the mobitronic to the compressor. If shorepower is available, the battery power is disconnected from the compressor and the mobitronic acts like a battery-charger to supply the compressor BUT AT 24VOLTS instead of 12. It just means that the current is lowered and components can be smaller. Just be aware of what you should be looking for under the particular operating conditions, and remember to measure AT THE COMPRESSOR TERMINALS (not the mobitronic output terminals). Did you install it? Do you where all the inline fuses are?
I'm not sure if Ken's unit is a Waeco or not, but you will be aware of the compressor varying it's speed between "economy" offshore and "fastfreeze" shorepower .
 
Ahh, that helps to explain things. I (naively) assumed that the diagnostic LED would be on if power is on and no faults found. So, it looks like the LED is probably working correctly after all.
 
No, the unit came with the boat. I did my measurements at the compressor terminals but with them disconnected from the compressor (easier access) which I have since found out was a mistake.

There is only about 20cm of wire between the mobitronic and the fridge and there is an inline fuse on it (which I have checked). Still, your assertion that the mobitronic supplies 24V means that when I thought I was testing the fridge on shore power (in order to eliminate my batteries from the equation) I wasnt because I was reading 13ish V.

So, my next course of action is to redo my voltage checks at the terminals while still connected to the compressor and while powered by shore power. If that shows over 24 volts then the problem must be the compressor, meaning I need to dissassemble it and send it off for repair.

Thanks guys for your help. i'll report back once i've got more info.
 
Hi All,

I've redone my measurements and have got results that make more sense:
(all readings taken at the compressor terminals)
With shorepower on, I am indeed reading 24v and the compressor works!
Without shorepower, I am getting 6v with the compressor connected but 12v with the compressor disconnected.
i.e. The battery power is losing 6v at the compressor when under load, however the rest of the boat seems to maintain 12v.
Am I right in thinking that this means there is a poor connection in the wiring somewhere between the compressor and the battery? If so, I guess I can take test readings at key points in the circuit to determine if the weakness is upstream or downstream of the test point.

Does all this sound correct?
 
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