Trane Gas Forced Air Furnace Fan Relay/Limit Questions


Old 03-11-16, 10:48 PM
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Trane Gas Forced Air Furnace Fan Relay/Limit Questions My Shot at Replacement Control Board Fan Limit Original Relay Original Relay Trane Vs Original Furnace Model # Trane Replacement

My Trane 1980 Furnace had a blower motor issue. The Motor was original and was replaced. This is a single speed control board. Only 2 wires from the motor used. White and black(medium High). I had the Fan ON at the thermostat. New fan was working. Swithced over to Auto. As soon as the heat rose enough for the fan limit to trigger the Fan Relay I could hear the Limit click and the Fan Relay made a high pitched noise/pop. When I switch back to fan ON the fan runs and blows heat although the old relay gets hot. Called Trane got a replacement. The replacement does not have the same amount of contacts on the back. I plugged it in and it did not work. Wouldn't even run with the controls ON. Spoke to Trane they only know what the computer tells them. I saw the wiring diagram on the back of the relay. I tried get a relay with the correct wiring diagram. It is correct but I am not sure what all the Numbers on the sticker mean. My Fan limit does not seam to have a problem moving. Do you think I have the wrong Relay? Do you think it could be something else?
Any help would be greatly appreciated.
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Old 03-12-16, 05:32 PM
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Welcome to the forums.

When I switch back to fan ON the fan runs and blows heat although the old relay gets hot.
Yes.... that is correct. That relay turns the blower on when A/C is activated (if installed) or when the stat is in the FAN ON mode.

Usually two different speeds are used. High speed for A/C and FAN ON..... and a slower speed that is activated by the fan limit switch and is for heat only.

I can't see the numbers on the two relays in your comparison picture but it looks like the wrong relay. There are number on both relays. You should have contacts in the same place as the old one. Your replacement is missing one of those terminals.
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