Goodman heat pump blows fuses

The defrost temperature sensor resistance will vary depending on what the temperature is that it is reading. If you have one cold and one hot..... the resistance reading will not be the same. You need to have the DFT wire disconnected from the control board when measuring the resistance. You measure the resistance strictly across the sensor without the board changing it.

Both those sequencer (W) terminal resistances are ok. Neither of those values will cause a short.

In order for the low voltage fuse to blow..... you are looking for anything that measured to ground reads down near several ohms. Under 5 ohms is considered a short. 60 ohms will not blow the fuse. 180 ohms to ground will not blow the fuse either.

Your heat sequencers are connected to the W thermostat wire. That W wire is the same wire that also connects to the W on the defrost board. If you run your thermostat on E heat.... only the W wire will be energized with 24v and the sequencer operates. When you have your unit in heat pump mode.... the compressor operates to heat. When the compressor cannot keep up with the heating demand...... the W line is energized and then the heatpump and the electric heat both run until the heatpump catches up.

So it's good you are checking things but you need to find something that is almost grounded. Something that measure near 0 ohms.

If your E heat works without blowing the fuse.... your W line is not a problem. If the defrost sensor was bad or shorted..... you would have a defrost problem but the fuse would not blow

Merry Christmas.

 

Hi Pete. The problem is still unsolved. A tech came today and checked my unit. He could not find any short in my system. He checked for obvious short but didn't find anything (I was still charged for a flat fee which is bad). The unit didn't blow fuse when he was checking. I told him the unit run fine in E heat mode. It often blows fuses after running a while (one to few hours). He said it died when the unit went into defrost mode and suggested to change the defrost board and the ambient sensor for $300 labor LOL. I asked if he can confirm that these changes would solve the problem but he can't. Anyway, do you have any idea what could cause the unit to blow fuses after a while (NOT instantly)? Bad solenoid coil, temperature sensor, etc? I am also planning to rewires all the wires in the heat pump unit. This at least will remove the short problem due to wiring at heat pump. Any suggestions would be really appreciated.

 

Ok...... here's how I handle these kinds of problems. It's up to you if you want to follow it.

I'm fairly certain the defrost sensor can't cause the fuse to blow. I'm fairly certain that the defrost board itself won't cause the fuse to blow unless the back of it is hitting metal.

No need to change any of the high voltage wiring. You're interested in the low voltage wiring only.

There are two suspect items. The contactor and the reversing valve. I put a temporary 2A fuse and fuseholder on each one. Then I watch and see which one blows. Put the fuses near the defrost board.

 

Thank you very much for your suggestions. They make more sense to me than the suggestions by the tech that stopped by yesterday.