refrigerator defrost timer

[hickeydrf]

I have just replaced the defrost timer on my hoover fridge freezer. However the timer is still not functioning. My suspicion is it is not being powered. I've read a lot on line about testing the various components of the defrost heater but nowhere has anything mentioned how the timer is powered. The fridge functions and I believe the power to the compressor has to pass through the timer and the timer diverts the power from the compressor to the heater to defrost the coils but how is the electric timer powered or is there somting else I have to do to activate it?

This is an extract from the "How to repair appliances" on this site.

The defrost timer controls the defrost cycle of the appliance. The timer runs continuously and roughly every six hours, shuts off power to the cooling system and sends power to the defrost heater. As the timer advances the heating element shuts off and power is restored to the cooling system. If the timer does not advance, the appliance will be stuck either in defrost or refrigerate mode, resulting in, respectively, warming or frost build-up.

How does the timer run continuously??

[richapplyguy]

There are 5 pins on the defrost timer. One pin is isolated from the other, the middle terminal of the other pins should have power measured between that pin and the isolated one. If not you have a bad wire somewhere.

[hickeydrf]

Thanks for your reply. I went looking for a bad wire and found a fuse in the heater circuit was broken. I bypassed the fuse and the timer started wirrrring away. I'll now run it through a 6 hour cycle and if all is ok I'll see if I can purchase the fuse. I suppose it's likely the heater is faulty if the fuse has blown. The resistance across the heater is 300 ohms. I also checked the thermostat which appears to be working (closing at low temp and opening at high temp).

Regards

David

[richapplyguy]

If a black steel case heater look for a short to ground. If not you may have a burnt/shorting wire near the element.