Furnace Blower

[Anonymous]

Posted by: Jimbo (old forum transfer)
Posted - 03/02/2002 : 13:30:45

5-yr old Carrier HVAC. Overnight temp set to 63, so when I got up this morning and house temp was 60, I knew there was a problem. I could hear burners coming on, then going off after warmup. Turned fan from auto to on, but blower still didn't come on. Checked filter; it was somewhat dirty, but you could see light through it, easily. But replaced it anyway. An hour later, furnace came back on, working apparently OK, and has been for about 3 hours.

Will a barely-clogged filter cause a blower to overheat and shut itself down? If so, should I pay for a service call to make sure it's not damaged, or just hang loose and see if everything continues to work well?

[Anonymous]

Posted by: Wgoodrich
Posted - 03/02/2002 : 13:53:42

I doubt you will find the filter as you discribed would cause a motor to overheat.

I would lean on a bad bearing or weak motor or bad connection.

This bad connection may be in the furnace supplying power to your or may be a contactor with a bad connection or contactor point. Remember that you have an HVAC thermostat that is low voltage and the fan is high voltage so you have a transformer and contactor in your furnace so the low voltage controls the high voltage. A bad connection in your thermostat can fail to activate the contactor in your furnace to make the motor run. This is a common happening that matches what you discribe, also.

Try your switch on your thermostat that turns your fan on constant. See if it makes the fan come on while the furnace is not calling for heat. If it works then I would wait to see if the fan motor fails to work again. If it fails to work again enter the furnace where the fan motor is and see if the wires going to the motor is hot or not. If the wires are feeding power to your fan motor then you have a problem in your motor. If the wires going to the motor is dead then look for your contactor that supplies power to the motor and see if you have power on the line side and hte load side of that contactor and also look to see if the contactor is making contact on the high voltage side. If the contactor is not closed then check for low voltage present on the contactor's magnetic coil. If no voltage on the magnetic contactor is present pulling in the contactor then you are back to a bad connection in the fan switch or the thermostat.


One of those ideas should be where your problem is. Sounds like an intermittent problem leading you to believe a bad connection somewhere in the low voltage or high voltage system. More likely low voltage [thrmostat circuit] that high voltage [contactor and fan switch]

I would wait to see if your problem reappears then try the ideas above.

let us know what you find.


Good Luck

Wg

[Anonymous]

Posted by: Jimbo
Posted - 03/02/2002 : 21:33:11

Well, I don't have the knowledge tools to go prowling around in there, but I sure hope you're right that it's a contact or relay or somesuch. Am having a repair person over Monday, so as to avoid weekend charges.

[Anonymous]

Posted by: Jimbo
Posted - 03/06/2002 : 21:38:14

Well, it was the "logic board," the guy called it. And would you believe it? The first time I've ever been one week on the good side of a 5 year warrenty

[Anonymous]

Posted by: Wgoodrich
Posted - 03/06/2002 : 21:55:09

Congrats you won one for the good guys. Glad you came out alright.

Wg