Fan Center Relay

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Old 07-04-10, 09:13 AM
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Fan Center Relay

Sorry for the long post...

I have an old Stewart-Warner gas furnace with a newer Gibson compressor/condenser. The other night when I came home I noticed the a/c hadn't been running. No breakers were visibly tripped. I checked the Fan Center Relay and no voltage was present across R & C (read somewhere that should be 24v).

I went ahead and replaced the Fan Center Relay (R8239 A 1052). When I turned the breaker back on to the furnace, the relay hummed really loudly and nothing else happened. After troubleshooting for a while, I figured out if I disconnected the two wires running to the outside unit (they were connected to C & Y), the furnace would operate correctly when I flipped the breaker on. The blower worked etc., just no outside unit obviously.

I flipped the breaker for the furnace and the compressor off (I had not reset the compressor breaker before), hooked the two wires back to C & Y and then cycled both the breaker to the compressor and the furnace. It worked. Ran fine all night.

This morning, the first time it kicked on, the compressor ran for 2 seconds and then shut off. The Fan Center Relay appears to be cooked again (no low hum, no power etc.).

I am stumped. Any ideas? I'm pretty much resigned to a long, hot weekend and then trying to get someone out on Tuesday to fix it.

Appreciate any help!

Steve
 
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Old 07-04-10, 09:53 AM
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Fried fan center

I suggest starting by checking/replacing the wires between the fan center & the condensing unit. A short in those wires is often the cause of burned out transformers. A fuse (5 amp automotive type) in line with the "R" will often save a transformer.
 
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Old 07-06-10, 08:12 AM
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Right on Grady,...

Rodents are well known for eating into your control wires to the condenser and could be the reason for the short. Also check the condenser safety's like the low and high pressure sensor wiring, usually yellow and blue wires in series with your condenser contactor for any bare wires touching metal.

I bet its in the wiring from the fan center to the condenser just like Grady said.
 
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