Central AC electrical overheating smell


Old 06-08-01, 08:20 PM
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Ok, fellas..
Bare with me a sec..I have an old central a/c unit in the attic. While inspecting it, i smelled the old familiar overheating smell of something electrical. Doing the old sniff test, i found the smell coming from the small box the power source goes into. Inside that box were two smaller things... The one that was emitting the odor was approx. 1" x 1" x 1 1/2", plain brown insulted matchbox looking thing with four wires coming off of it. It definitately was hot. The only writing I was able to make out on the box was Logan Portland 9105 I am very mechanical and I'll be doing this swapout myself. Any help you can lend will be greatly appreciated.
My questions are:
1. What is this box?
2. Is it an expensive part to buy
3. Once i buy the replacement, how in the heck do i know if the wiring configuration is the same?
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Old 06-09-01, 05:02 AM
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Sounds like

fan relay.If so coil has fried.2 wires should be 120volts to supple power to fan.The other 2 are 24volts.When tstat calls for fan or fan/cooling 24volts energizes the coil.makes contacts,which in turn send 120volts to fan motor.The 2 thinner wires are 24volts,the 2 thicker wires are 120volts.Mark and label all wires before removing.REMEMBER,power off for repairs.PDF
Old 06-09-01, 05:29 AM
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Thanks, PDF,
Is this part expensive, do you think? I recently had the limit switch changed out. Could there have been something done wrong in that replacement that have caused this relay to go out in 3 days? Before the limit switch was changed out, the unit was operated by flipping the breaker to turn it off and on. Could running the fan for too long of a time caused the relay to wear out? Thanks again for you help.
Old 06-09-01, 07:13 AM
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should be around 25$.It is starting to sound more like relay since you have had to shut off main power to stop unit.Can't tell you from here if problems are related.PDF

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