The Virtual Repairman's Appliance Help

[Bman.]

Good afternoon-

My heater : Bryant (25 years old +/-).
Thermostat : Digital (upstairs)

Here is my situation. Everything runs as it should right up until the burners turn off. The heater will run until desired temp is reached, the burners turn off, the blower fan continues for a few minutes and then shuts down.

3 seconds later, the blower turns on.... runs for 2 seconds and then turns off.

That's it. Why does my blower cycle up and run for two seconds at the end of the heating cycle... more importantly, what can I do to fix this?

Seems like a faulty heat sensor or something?

Any help is appreciated.

[Virtual Repairman]

These furnaces use a fan limit switch which consists of a long probe and a rotating sensor within the probe that controls the fan. When these wear out, the coil no longer retracts and stays retracted when the source of heat stops. Instead, it creeps back around and starts the fan to short-cycling. The simple solution is a new fan control. See someone in your area who sells A/C parts to obtain the right one for your Bryant. They are very common.

What a Fan Limit looks like-

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[Bman.]

Thanks for the quick reply! Awesome.

See the attached images - see if I can actually find the part online and locate which part it actually is on the case.

I think I have the model correct:
394GAD060150 (394GAD060150AEEA = product)

Where can I find the fan limit switch? Any how difficult are they to replace? I imagine it's plug an go.. but getting to it may be more difficult.








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[Virtual Repairman]

The limit does not appear to be in your pix, unless it is right behind the shot of the gas valve (too dark to tell). There are usually 4 wires going to it, 2 for the fan and 2 for the low-voltage circuit to the gas valve.

I recommend you do not touch or try to adjust this part, and you should use your model number to obtain one first before going further. Any decent A/C supply house or online store will have one. That's a bigass furnace

Be sure you do not have any of the ceiling registers closed off in the house, or the heater cannot effectively cool down as it should. All registers must be open to allow the heater to cycle off and on properly. After all, your furnace was made in 1987, so it is not uncommon for parts to wear out after 30+ years .
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[Bman.]

Yeah, the old furnace size matches my flipping utility bill about right too. It wouldn't be so bad if my wife didn't keep the heat cranked to an Sahara desert type of hot.

I will get my local HVAC folks out here to take a peak.

Everything is open and should be cooling correctly. So who knows? Sitting all summer must have done it in.

[Bman.]

Here is an easy question -

How critical is it that I get this fan limit switch replaced? When the limit switch goes completely out am I going to be stuck with no heater?

I am ultimately trying to determine the urgency of this issue.

Thanks-

Benjamin.

[Virtual Repairman]

it is not critical at this point, merely an annoyance.

The worst that might happen is the fan would stay on rather than shut off. Take your time about getting it replaced as long as you can ignore the cycling of the fan.
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