GE Zoneline Vertical Heat Pump Help

gezone

I have a GE Zoneline vertical heat pump model #AZ91H12D3C-W1 installed in a condo that is on the fritz. I woke up freezing one morning and noticed no power at the thermostat and after checking the breaker and fuse on the unit, I ended up calling a local HVAC company to come take a look. The technician looked at the unit for less than 2 minutes, didn't try to power the unit on or remove anything except for the unit cover and diagnosed a failed control board and quoted me $1680 for the fix. I passed and started doing research to see if I could fix it.

I took the control board off and noticed the 10A fuse on the board was burned out. I replaced the fuse, plugged everything back in and turned power to the unit back on. Everything powered on ok and then when I switched to HEAT, the fuse on the board blew instantly. I thought maybe the technician was right so I bought a new control board online for $250 and replaced it for only the same thing to happen again.

At this point, I began trying to troubleshoot. I tried the following:

1. I took measurements at the breaker and the control board and voltage is correct up to the fuse. Couldn't measure past it due to space limitations.
2. There was a simplified schematic on the unit cover - I checked continuity across all accessible circuits and measured voltage where I could. All is ok. The unit's capacitor is also ok.
3. With HEAT/COOL OFF and FAN in AUTO, the control board fuse does not blow (obviously cause nothing is on).
4. Turning the FAN to ON - control board fuse blows instantly.
5. Turning HEAT to ON (FAN AUTO) - control board fuse blows instantly.
6. Turning COOL to ON (FAN AUTO) - control board fuse blows in 20 or so seconds.
7. The 20A unit fuse never blows - just the control board fuse.
8. The display on the unit only shows two error codes, 14 and 24. Both of these are unused according to the manual. I'm confused about this one.

I'm pretty certain at this point there is something wrong with the fan motor so I unplugged the fan from the control board and retried all of my tests - the control board fuse never blew.

I looked everywhere online but I can't find any similar issues or really any troubleshooting information on this unit. Can anyone tell me if I'm heading in the right direction? Are there any fan contacts deeper in the unit that can be causing this issue and not the fan motor itself? The unit is installed on the second floor in a closet where the walls were built AFTER it was installed so doing anything to fix it will be a challenge. Hoping to get some advice before having to do any surgery. Thanks!

mattmia2

certainly sounds like the fan motor is shorted but would need to see the schematic.

gezone

Here is the schematic. If it is the fan motor, are these easy to replace on PTAC units?

mattmia2

Could be a bad capacitor. Normally it would trip the overload on the motor when it doesn't start but in this case the fuse on the control board could be the overload protection on the motor. Does the motor spin freely? You can try disconnecting the fan terminal on the capacitor and see if it still blows the fuse. If it doesn't then it is probably the capacitor but if it still blows the fuse it could still be the capacitor and it blows the fuse because the motor didn't start. if you disconnect the cap and give the fan a spin as you energize it, it may start and not blow the fuse.