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Dianne4098
Furnace blower won't run
Dianne4098

When I turn the heat on, my furnace just hums. It would take a few seconds to "warm up" in previous years before the blower actually started blowing but I have let it hum for a minute or more & it doesn't come on. The a/c works fine, now and this past summer, but I did have to turn it off manually b/c it wouldn't shut off by itself. Any ideas what it might be? I have an old dial t-stat, not programmable one, just in case that's important.

Thanks

function
Re: Furnace blower won't run
function

Time to go check out what the error code is on the system. You can google the service manual for your furnace if you do not have it, and then proceed to look for the error codes. It may be a bad blower motor or a number of other things, fortunately most manuals will have a troubleshooting guide.

dj1
Re: Furnace blower won't run
dj1

In addition, you need to have the unit inspected, as you could have one or more faulty components. Call a tech.

If you have experience and want to do it yourself, start with the t-stat. If it's old, replace with a non-programmable one. Make sure all wires are correctly installed.

From there, you could have a bad gas valve, bad igniter (or pilot light if it's an old furnace), bad blower, bad circuit board, and so on.

This is not job for a novice, guessing/replacing the wrong parts will cost you more and drive you crazy.

Dianne4098
Re: Furnace blower won't run
Dianne4098

Thanks for the input. It is an old furnace, about 25 yrs old. 1 more question...is the hot water heater pilot light in any way connected to the pilot light on the furnace? Just curious.

Fencepost
Re: Furnace blower won't run
Fencepost
Dianne4098 wrote:

Thanks for the input. It is an old furnace, about 25 yrs old. 1 more question...is the hot water heater pilot light in any way connected to the pilot light on the furnace? Just curious.

Only by the gas supply line. Otherwise, they are two separate systems.

Your furnace may have a faulty fan/limit switch, which is failing to start the fan when the combustion chamber reaches operating temperature. You may also have a faulty blower motor.

Do you have a "fan" switch, either on the thermostat or on the furnace itself? If you turn that switch on, does the blower start? If not, you may have a faulty blower motor or relay.

You should probably call a technician.

ed21
Re: Furnace blower won't run
ed21

Ditto call a HVAC company to have it checked. The a/c not turning off and the humming with heat may or may not be related. Time to get it fixed right.

A. Spruce
Re: Furnace blower won't run
A. Spruce

I have had similar problems with my furnace, both with the hum and with poor operation.
1 - bad thermocoupler
2 - bad fan switch (multiple switches, actually )

As has been said, let a professional handle it, as most items on a furnace are not DIY. While the items mentioned don't seem like a big deal, unless you know how to test for them and how to install the parts safely and correctly, you're simply going to cause yourself even more heartache.

dj1
Re: Furnace blower won't run
dj1

I knew that your furnace is old. At 25 years, it's inefficient, probably noisy too, and starting to break down. You keep it and it will drain your pockets.

Fixing it will cost you time and money as I said, but if you have the money, go get yourself a new furnace. You can keep the a/c and heat exchange, just replace the furnace.

Last winter I replaced two of them and I chose RHEEM. The furnace can be any brand, doesn't have to be the same brand as the a/c, just try to find one the same physical size, so no installation modifications will be needed.

However, if you ask HVAC contractors, you won't many of them willing to replace the furnace only. It has to do with warranty and $$$.

ed21
Re: Furnace blower won't run
ed21

I added a furnace to replace a heat pump. I kept the a/c side and outdoor unit until I had it replaced many years later. In my case the heat pump performance was marginal, but the a/c was okay.
My point is companies will generally work with you and you can possibly spread out the cost over years if needed.

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