[gilkelley]

Let me start out by saying I am taking an open book training program and I am having trouple keeping (or maybe just getting) my head straight. I have a question that has me stumped and I am letting it get to me.

QUESTION: The refrigerator is not cooling. You find a frost build up on the evaporator coils. The compressor, condenser fan, and freezer are all runniing normally. When you advance the defrost timer manually to the defrost mode you read 120 volts on the defrost heater and the current draw is approximately 3 amps. The failure is?

(a) defrost heater
(b) defrost timer
(c) defrost thermostat
(d) temperature control

That is all the information they give me. I have talked myself into figuring that under the conditions all are ok.....The defrost heater works because you have 120 volts across it and 3 amps of current......The timer works when you advance it manually......The defrost thermostat is working or you would not have current flow.....and the temperature control is working because the compressor circuit was working......My only thought is that the defrost timer was not advancing, but before you manually advanced it you should have had cooling from the compressor circuit..............WHAT AM I MISSING.

Please tell me what you think is wrong and why.

Thank You

[kayakcrzy]

If you get 120 volts coming to the heater, and the unit is not defrosting, then the heater is your problem. Always remember the way voltage flows. LINE, LOAD, CONTROL, and RETURN. If you ever check any part, and you have power coming to it, and it does not function, then that conponent is your problem. If you need me you can reach me at my web site, at ApplianceEducator.com Tom

[gilkelley]

Thank you for your reply....I questioned the heater myself however when it stated that I had 3 amps of current that told me I had current flow thru the heater.

[woodchuck]

The defrost timer is your correct answer. The timer wasn't working thus the ice buildup. The compressor and other components will still work but the air flow is disrupted and the ice traps the cold in the evaporator.

[denman]

I'll throw my 2 cents in, I also vote for the defrost timer
Blown motor coil or a stripped gear

[kayakcrzy]

Denman or woodchuck, I have a question for you both. I don't use a amp probe, it just seems to me like 3 amps is low for a heater, can either of you gentlemen tell me the wattage of a defrost heater? I would hate to spend 50 bucks for a amp probe to prove myself wrong. LOL! but if either of you guys, can tell me the wattage of the heater, we can do ohms law, and figure out the amps, matematically. Tom

[woodchuck]

I don't do amps. I actually wouldn't have measured the voltage. I would have observed the heater when I advanced the timer. If it did work I check the timer. If it didn't work then I check voltage going to it. In his classroom problem just like peoples description of their problems some information is lacking and more questions need to be asked.

[denman]

Put your finger on the heater it will tell you if it is working real quick.

You are getting 320 watts so the question is , is this enough which depends on: the heater design and the coil design and the fridge size and probably a bunch more I do not know about.

I also do not own a amp probe, I have used the amp setting on my meter but only when working with solid state low volt, low amp circuits. Never seen a heater
coil/element draw low current. If there is a spot on it that does restrict current re: a higher resistance. It will overheat at this point and blow the heater open.