Goodman GMPN080-4

[kcamp99186]

Hi. This is Ken Campbell and I'm new to the forum.

I have a Goodman Furnace GMPN080-4 that is blowing the 3A fuse on the control board. The issue is the AC won't work. I replaced the fuse only to have it blow when power was reapplied. Thermostat calls for cooling but I have nothing. AC and furnace breakers are ok. Furnace fuse is good too. I can manually operate the contactor on the condenser and confirm that it is working. Can anyone point me in the right direction please?

[leamy]

contactor winding may be shorted. common issue .. ants, moisture, Chinese crap design....

try disconnecting the 24 volt connector on contactor and see if fuse pops

 

Leamy

[Hiroshi]

So by "confirm that it is working" means both the compressor and condenser fan motor kick on when you "manually" operate the contactor? For the contactor to work correctly it needs to be able to close itself...

1) A demand for cooling is initiated. · The control checks for an open limit. If an open limit is detected the furnace will remain inoperable until the condition is corrected. During an open limit condition the circulating air blower will be energized. The status light will blink four (4) times. ·

2) The condenser contactor will close. ·

3) After approximately five (5) seconds the circulating air blower will start on the cooling speed. ·

4) After the room thermostat is satisfied the condenser contactor will open. · The circulating air blower will remain in operation for approximately sixty (60) seconds.

If you are blowing fuses at step 2, what Leamy says makes sense- because that 24v circuit has to pull the contacts together before anything receives power...and you have been testing it "manually," I am guessing that means you are pushing the contacts together yourself?

[kcamp99186]

Yes, I do mean pushing the contactor closed by hand and the fuse blows immediately when power is switched back on. I replaced the fuse with a 5A, all I had left, just to see if it would blow and the AC ran fine.

I believe the thermostat wire is bad. I had spliced it several years ago where it wore against the frame. While it was running again, I decided to check it and the compressor shut down as I moved the wire about. Wiggling the wire caused it to start back up again.

I've shut it down and am replacing the thermostat wire today as well as the power wire from the outdoor shut-off. It has some damage as well. Does it sound like I'm on the right track?

Thanks for the help.

 

[alamo1718]

It sounds like a broken/shorting low voltage wire. When you install the new stat wire, feed it through some clear plastic tubing to protect it, before you install it.  You could even get real fancy and use some blue PVC conduit, ENT, from lowes or home depot. The ENT has ends that will screw into the control box and really protect the low voltage wire. I've even seen the wire sheath that you see in cars added after the wire its installed.   Don't forget to replace that 5 with a 3 amp fuse. It is sized to protect the transformer and other components. If it shorts again with the 5A still installed, it could take out something else. 

[leamy]

did the same thing a few years back came back to a open low voltage transformer and a finally totally smoked contactor.

check the contactor, or you may be back with more parts...

[kcamp99186]

Thanks so much guys. I found that the stat wire was rubbed bare inside the case. Must have been from vibration over the years. Replaced both the thermostat wire and the electrical cable. Put the electric in liquidtight conduit. Didn't think about the Thermostat wire. Will redo that soon! Good idea. And have replaced that fuse as well.

Appreciate the advice.

 

[Hiroshi]

Nice shooting, Alamo!