fridge not "waking up"

[Lyra]

Bavaria 36, 2004
Danfoss BD35 compressor

When I turn on the fridge power, the compressor (and the fan inside the cooler compartment) operate for a few seconds and then stop. Leaving the switch on - this repeats itself (did'nt take the interval time, roughly 1 minute).
No problem of thermostat - I replaced in the past the original with an electronic unit and I see that the relevant terminals on the controller are shorted, so fridge should work.
Battery voltage - around 13V so should not be the problem

Suspects:
Defective controller (never opened one so don't know what could fail in it)
Defective compressor (maybe over current causing shutdown and the controller has some kind of recovery period that it tries again?)

Any ideas?

[SorinCT]

Danfoss compressors usualy have a diagnostic mode. If you check in the manual for the compressor, you rig a 12v bulb to one of the + and the - and the frequency of pulses indicates the trip/alarm. That can be over-current (also excessive heat on the motor is indicating that), low pressure cut-out  or high pressure cut-out.

[geoff]

Sounds like the low volts cutout. When the compressor starts it draws a fair bit of juice ,if there is a high resistance joint/switch in the line from the battery it will drop the voltage below the 10.5v in the blink of an eye[too quick to see on a multimeter. Wire the battery direct to the fridge . I had this problem a while ago ,a rewire cured it.Geoff

[SorinCT]

Sounds like the low volts cutout. When the compressor starts it draws a fair bit of juice ,if there is a high resistance joint/switch in the line from the battery it will drop the voltage below the 10.5v in the blink of an eye[too quick to see on a multimeter. Wire the battery direct to the fridge . I had this problem a while ago ,a rewire cured it.Geoff

That can also be tested by changing the external resistor wired to the controller.

[diverphil]

wire a bulb up or test light to the correct terminals, info can be found on here somewhere or on internet, i cant remember them from when we had a fault, that will give you an indication of what is causing it to cycle, but first off check the voltage at the ecu or controller as it can drop on start up if you have a bad connection. If you use the test lamp and it doesn't blink at all then the controller has failed, that is what happened to ours, new unit was around £60 easy to fit.

[diverphil]

just had a quick look for controller, there now banging them out at  £124, that's gone up a lot in 2 yrs, have a look at my post there is a link for the part in ynmars reply. search for" fridge packed in" in the search box at the top.

[Lyra]

Thanks all
Slipped my mind that due to the age of the boat conductors may have badly corroded along their length (had it on wires that went out like nav lights, but not inside the boat) - will test on Saturday a direct connection to the battery.

[Lyra]

Tried today direct connection from battery - same thing.
Thinking more about it, I do not think it is a mater of supply voltage drop because I think that would have prevented the compressor from working at all, since the ignition current (an voltage drop) would occur on the very beginning, and I see a ~3 seconds operation before turning off  - but I still do not discard this possibility (maybe the controller has to sense the voltage drop long enough before turning off).
Going further I would like to disconnect the controller from the compressor to check it offline - before doing any damage - is the white plastic a whole connector that should be pulled out, or is it a socket into which the 3 individual wires get plugged?

[geoff]

The connector is levered out sideways ,it fits over 3pegs in the compressor body. bloody tricky . Geoff

[Lyra]

Not much of an advance
After consulting another group someone said to make sure that the condenser fan (the one next to the compressor) works, as if it is not then the controller stops.
Checked the fan and indeed it did not work.
Dismantled, cleaned it, connected to 12v and it worked. In any case also ordered a cheap fan from Aliexpress.
Went to the boat today, connected the Chinese fan, turned everything on and it worked. 
Switched to the original fan - still worked.
Let it work several minutes and made sure that it not only works but also cools - looked OK.
Tidied up all connections and checked again - back to square one.
From that point on - could not get to the point where it works.

So at this point I know the compressor itself is OK and the problem is within the controller - just do not know what the problem is. Could be a problem with the driving circuit.

[SYJetzt]

Try to use the chinese fan once again. If the original fan has too much friction and draws too much current, the controller will cut out. There should be a value for the maximum current draw of the fan somewhere in the specs of the controller. If the problem is the fan, replace it with a original fan due to the high airflow demands of the condenser.