Rheem heat pump help

[vavet]

A couple weeks ago, we noticed the house feeling colder than usual, checked the thermostat. It was set to 70, but inside temp was 66. We set to emergency heat (propane, not electric resistance) until we could get it sorted.
i found the 3a fuse for the control circuit on the indoor unit open. It immediately (within 3 seconds) blows when regular heat is selected.
the reversing valve reads 16 ohms. The contactor control circuit reads 15 ohms.

if I press in the contactor, the outdoor fan runs. After releasing the contactor, I can hear gas equalizing, so I believe the compressor is also running. The 2 LEDs on the outdoor unit control board blink together. That means everything is ok according the table on the board itself.

I shotgunned an outdoor unit control board with no luck. The LEDs on both boards have the steady blink.

I had a soft start unit installed on it to help with starts when running on generator power, but I’ve removed that to eliminate that as a possibility.

i think now it is either the RV solenoid or the contactor. Note this is a rheem unit, so the RV solenoid is energized when calling for heat unlike other brands.

i Removed the Thermostat and jumped the contacts for fan and RV to the 24v power. The fuse blew.
I replaced the fuse and selected ac on the thermostat. The fuse blew.

my belief now is the contactor is drawing too much current, despite ohming at a reasonable level.

any other ideas?

 

[PoorUB]

any other ideas?

Unplug the control wire to the contactor, drop in a new fuse and try again. If the fuse holds toss a contactor in it.

 

[PWC Repair]

Unplug the control wire to the contactor, drop in a new fuse and try again. If the fuse holds toss a contactor in it.

This sounds like solid advice.

 

[bonneyman]

Could be a thermostat wiring short. Might be worth a look.

Sorry - edited response.

 

[vavet]

disregard…I’m an idiot. i never plugged the disconnect back in. I did it tonight, but the fuse blew as soon as I selected heat. The compressor and outdoor fan run if I manually push the contactor in. I double checked the connections on the control board and on the contactor. Everything looks like it is where it should be. The reversing valve ohms out at 16 ohms. I’m at a total loss.

New 3a fuse in. Turned to regular heat, bumped up t stat a few degrees. 6min and 40 seconds later, the indoor fan unit comes on, I’m thinking….yay, I won.
not so fast. The outdoor unit is not running. Not sure why, air is blowing inside, but it’s just the same 70 degree air already in the house. It’s not warm. At least the fuse didnt blow. That good.

I either messed up something when I replaced the contactor or when I removed the soft start device, it started pouring rain, so didn’t get to look at it any more.

 

[American Locomotive]

It sounds like you may have had a bad control wire going to the outdoor unit, and the short finally blew open?

 

[Bert_]

Just start unhooking things until the fuse doesn't blow. You won't spot the failed part with a visual check.

Your problem is in the control circuit, do not spend any time looking at the larger high voltage wires.

Sometimes reaching in and wiggling wires with everything powered up will locate an intermittent problem.

 

[Ohmthis]

I’ve seen this many times. Usually a geranimal of some type have chewed wires. The problem is in the little wires out to the HP. Do you have a tester that can do AC voltage? The control circuit is24v ac. Her are the typical colors for control. Red 24v, blue 24 v common, white furnace heat, yellow compressor (ac and HP), orange RV. Look at the wiring as it comes out of the house (it’s typically taped to the line set. Look for damage. Look where it goes into the unit for damage. Write the wiring connections down. Undo your wires and with a good fuse and it in regular heat check for power on BL to R, BL to Y, Bl to O. You should have 24 V on all those wires to blue. if all is good, there, start looking at the control wiring in the unit. The yellow will connect through safeties, high pressure, low pressure. The red will go to a defrost board along with the white, the orange and blue. I think you will find either a wire damaged or Touching the frame. Let us know what you find.

 

[fitter30]

Disconnect the two control wires in outside unit doesn't matter if power is on or off for the test. Control voltage comes from inside unit. If fuse blows problem not in outside unit.
Thermostat wires in outside unit normally in a separate compartment attached to the rest of electrical. Disconnecting wires off a device take a picture of it first.
Outside unit has a few components. Defrost control, pressure controls and coil temperature sensor.

 

[ericm]

When I had the same fuse blowing it turned out to be the contactor. It still had continuity but the resistance was out of spec. When i removed it to replace it I could see where the coil insulation was burned.

 

[vavet]

Final update: I spent several more hours and blew a few more fuses. i swapped the 24v compressor wire between the AH and the outdoor unit with an unused conductor in that cable, thinking maybe it rubbed and shorted out. No luck.

finally figured out that it only blew the fuse when the compressor was called for and the line voltage was present at the outdoor unit (disconnect in place).

I finally caved and called the hvac repairman. I wrote him a letter describing what I’d done and replaced Since I wouldn’t be here when he was. He was here less than an hour. He found one of the wires running between the outdoor unit control board and the high pressure switch was rubbed through and shorting on one of the copper tubes inside the unit. He replaced it and secured it and we’re back in business.