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Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 854
Experience:  I have been an HVAC/R mechanic/technician for 30+ years.
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AF80MPA100B5-A I have this model furnace. the a/c runs

Customer Question

AF80MPA100B5-A I have this model furnace. the a/c runs for a couple hours then shuts down. I opened it up and I'm trying to find the run capacitor but I don't see it. I have pics, can you help locate it. FYI, the outside unit runs perfectly fine, its the blower in the attic that is in the furnace
Submitted: 1 year ago.
Category: HVAC
Expert:  Brian HVAC Guy replied 1 year ago.

Hi I'm Brian and I'm here to help!

Yes, please send the pics! In the meantime, I'll try to find some info on your furnace. Usually the capacitor is mounted directly to the blower housing near the end bell of the motor.

Thanks,

Brian

Customer: replied 1 year ago.
pic attached
Expert:  Brian HVAC Guy replied 1 year ago.

If that happens but nothing happens when you do the wire twist checks, then it's very possible the 24 volt transformer is blown. It is the device between the contactor and blower relay. Replace that and you may be golden.

Thanks,

Brian

Customer: replied 1 year ago.
what is the wire twist check?
Expert:  Brian HVAC Guy replied 1 year ago.

Sorry that was meant for a previous customer. I'll have a look at the pics. I haven't found an exploded diagram yet.

Thanks

Brian

Expert:  Brian HVAC Guy replied 1 year ago.

Sorry again for that errant post. That was an internet hiccup! The capacitor for your blower motor will be in the other section of the furnace from the pic you sent. The pic is of the burner section. If you remove the other panel on the furnace you should see the blower housing and controls inside and the capacitor should be mounted to the blower housing. I did find out it is a 15Mfd capacitor at 440 volts ac.

Customer: replied 1 year ago.
I'll have to go up and take a look
Customer: replied 1 year ago.
however, does the problem sound to you like it is the capacitor?
Expert:  Brian HVAC Guy replied 1 year ago.

Sorry for the delay, I had a response typed out and my computer display crapped. I had to get on another laptop!

It's hard to say, a blower motor won't usually run ok for two hours if the cap is bad. If the cap is weak, it might. Are there any other symptoms? Does your outdoor unit continue to run when the blower stops?

Customer: replied 1 year ago.
as I mentioned previously. outdoor unit runs fine, keeps running. No other symptoms, no leaks, no freezing, air is cold
Expert:  Brian HVAC Guy replied 1 year ago.

I just wanted to make sure the outdoor unit stays running when the blower quits. That wasn't very clear to me before. It would point to different problems depending on which were the case. Since the outside unit continues to run when the blower doesn't, it points to either a pretty weak capacitor, a failing blower motor or a failing furnace control board fan relay. If we could trouble shoot with a meter while in failure mode, we could determine which. If you have a meter with a capacitance function, the capacitor can be tested. Short of that, it's a replace and see scenario. The capacitor is the cheapest so I would try that first like you were about to do. If that turns out not to be it, then it's a toss up whether it's the board or the motor. An amp clamp meter might help but voltage probing with a meter during the failure condition is the only true way to see what's failing.

Customer: replied 1 year ago.
ok yeah thats all beyond me, I don't have that type of equipment. Still can't find the capacitor, I opened the other side
Expert:  Brian HVAC Guy replied 1 year ago.

I did find a manual and a parts list for the furnace but no exploded parts diagram in either. The capacitor should be mounted on the side of the blower housing near the the motor.