[shocker]

My heat pump wasn't working and I checked the thermostat and it was flashing heat on. I called someone who said the fuse was blown and replaced it to do troubleshooting. They came to the conclusion it was the defrost board which they replaced. They also replaced my thermostat. This occurred in the spring of last year. Early December the same thing happens my thermostat is flashing and I put it in Emergency Heat until a tech can come look at it. They did some troubleshooting and replaced the thermostat with another. Not sure what they did but it ran fine until this week! Same thing the thermostat began flashing heat on after it ran fine for over a month!

 

[jimn]

Sounds like they are fixing the symptom rather than the problem . Kind of like replacing a tire multiple time because the tread is worn on the inside rather fixing the suspension system . The only knowledge I have of heat pumps is from this forum and thanks to this forum you couldn't sell me a house with one of these if I lived in a northern clime where heat is all important . Lots of guys here who can perhaps offer some insight. But I suggest you might want to shop around for a company that actually employs people who can diagnose an issue .

 

[Bitters]

I agree with jim01. Changing the stat and defrost board makes no sense to me. Are you talking about the fuse on the control board in the furnace?

 

[shocker]

Yes the fuse in the control board. They troubleshooted the wiring and the going from the air handler to the outdoor unit and found nothing. If the system is in Aux heat it works with no issues.

 

[jeepgrady]

Just had a similar issue. Look at my post from several days ago, titled,"No Heat". Turned out a wire inside the outdoor unit was just touching one of the copper tubes. This caused a minute hole in the insulation on the wire. Apparently, under certain vibration scenarios, the bare portion of the wire touched the copper tube and shorted out causing fuse to blow.

 

[shocker]

That was all checked but could have missed something.

 

[Bitters]

I would double check the stat wires outside and in the unit.

 

[shocker]

Thats the thing thats odd both wires were checked for continuity. I was standing right there.

 

[Bitters]

Checking continuity won't tell that 2 wires are shorted together.

 

[supers05]

Checking it against an insulation tester may not yield results either, since it may only be shorting once every few hours of vibration. While rare, finding that kind of short can be fairly difficult

Cheers!

 

[gladiatormaniac]

I have serviced at least a thousand furnaces, not heat pumps but I know that when I show up to a customers house and the unit is working normal, and I try to make it fail by turning it on and off but it still works fine, then it is a intermittent problem that would take too much time to find. I can ohm test the thermostat wiring, but I can't test a control board unless is fails in front of me. Especially if I have 5 more customers to attend to that day. Changing the thermostat is a cheap fix

Sent from my XT1254 using Tapatalk

 

[gladiatormaniac]

But I would like to mention the best way to find intermittent problems with a thermostat is to check ohms from r to w at the furnace with one of the wires disconnected from the furnace. I had the customer turn up and down the thermostat many times. I had .6 ohms every time the thermostat had a call for heat, and than OL when there was not. But I have had random ohms to thermostats or swiches of any kind to tell me that the contacts are pitted.

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[DOUG1111]

What was the fix??????????

 

[beenthere]

Might have a low or high pressure switch's wire intermittently shorting to ground. Could also be the RV's coil is shorting out when it goes into defrost. Or the contactor's coil shorting at times.

 

[supers05]

Had a intermittent short just yesterday. We'd blow fuses very rarely with this unit, but couldn't figure out why. Finally got a black spot forming from the arcing. It was where the high voltage wires went through the box, and connector. Hidden by both the metal and the box connector, and ohmed out just fine. Would only short with very specific vibrations and wind patterns.

Granted this was high voltage (600v), so easier to find then low voltage, because the arcing causes more carbon buildup. However, it was still a pain in the behind to find.

Cheers!