80 volts to blower motor?
#1
Member
Thread Starter
Join Date: May 2011
Location: United States
Posts: 2
Upvotes: 0
Received 0 Upvotes
on
0 Posts
80 volts to blower motor?
Hi,
I'm having a problem with my American Standard Freedom 90 single stage natural gas furnace. I believe I have it diagnosed to a bad main board, or the blower motor. The unit fires up and seems to run fine. After about 45 seconds of it burning properly, it gives the signal for the blower motor to kick on and start circulating air, but the blower never starts. I measured the leads going to the blower motor. At first it's of course at 0. When it clicks to start the blower motor I'm reading about 80 volts. This should be 115-120, yes? At 80 volts, would the blower motor turn at all? Mine isn't even budging. Would it be safe to disconnect all leads coming from the blower to the main board, and then "hot wire" the blower with 115v to test it? Or if I'm showing 80 volts going to the blower is the problem definitely my board? Thanks!
I'm having a problem with my American Standard Freedom 90 single stage natural gas furnace. I believe I have it diagnosed to a bad main board, or the blower motor. The unit fires up and seems to run fine. After about 45 seconds of it burning properly, it gives the signal for the blower motor to kick on and start circulating air, but the blower never starts. I measured the leads going to the blower motor. At first it's of course at 0. When it clicks to start the blower motor I'm reading about 80 volts. This should be 115-120, yes? At 80 volts, would the blower motor turn at all? Mine isn't even budging. Would it be safe to disconnect all leads coming from the blower to the main board, and then "hot wire" the blower with 115v to test it? Or if I'm showing 80 volts going to the blower is the problem definitely my board? Thanks!
#2
you very well may have a bad control, but lets test first. what is the incoming voltage to the furnace? Turn your thermostat to off and select fan on... does the blower come on? if it does, then skip the rest. Turn the stat off and fan to auto, Next remove the black wire from x-fmr terminal on control board...then install black wire from the blower motor on the x-fmr terminal.... push in the door switch.... this will provide the motor with the same voltage as whatever is coming into the furnace. Does the motor start?
#4
Member
Thread Starter
Join Date: May 2011
Location: United States
Posts: 2
Upvotes: 0
Received 0 Upvotes
on
0 Posts
you very well may have a bad control, but lets test first. what is the incoming voltage to the furnace? Turn your thermostat to off and select fan on... does the blower come on? if it does, then skip the rest. Turn the stat off and fan to auto, Next remove the black wire from x-fmr terminal on control board...then install black wire from the blower motor on the x-fmr terminal.... push in the door switch.... this will provide the motor with the same voltage as whatever is coming into the furnace. Does the motor start?
#7
Sounds like you nailed it. I had a similar problem on a Carrier, at times it would go off on limit, voltage read showed low voltage to the heat speed( I've forgotten how low), pulled board and found bad solder joint on back side.