Freezer motor start problem

[Turnip]

Hi folks,
Have a large Zanussi chest freezer to try mend, so wonder if anyone is familiar with the system.

Freezers used either to have a relay or PTC on the start up winding to get the thing going. This one has a 4Mfd cap permanently in circuit, but seems nothing to start the motor.

Notice several small motors use the system where starting torque isn't an issue, but to start a freezer compressor usually takes a whole heap of amps initially then consumption falls to half an amp or so.

4Mfd cap checked OK (tried others) then found it would start with a 25Mfd but running current was around 2.5amps and the motor thermal trip cut after a few minutes.

Tried a 10Mfd and freezer started, current dropping to half an amp - Freezer freezing like a good one - bit puzzled - any thoughts ? - Chris.

Forgot to mention that peak current when it doesn't start is a mere 5 amps, and when I left it on all night, temperature dropped to - 30C as the thermostat was also duff. Suspect freezer running flat out for some while could have caused problems with the motor, as it now gets a bit hot. But there again, they always do.

Later -

As freezer was a Gumtree bargain, didn't get serious until couldn't get the seller to accept it back for a refund, and eventually the time ran out as he was never at home to accept it, and I couldn't prove that I'd tried delivery, for Paypal to do a refund.

Gather if used a delivery service, they would note he wouldn't accept it, and a Paypal refund would be the biz. Trouble was, a non refundable £50 fee for non delivery.

Found the PTC had burned out (as they do) so got a few from Hong Kong - Freezer now mostly OK, just an issue with the thermostat, where it doesn't cut out at -20C on the lowest setting and freezes Nitrogen.

Guess just a thermostat job, as contacts seem to stick. Took it apart and found nothing obvious - noted an adjustment screw, so fiddled a while and got nowhere as it doesn't cut out at any temperature lower than -10C

Found a new one on the Flea, not exactly a Danfoss, but a third of the price - Freezing in progress.