Heat pump not defrosting

[JoeMcG]

Hey guys, looking for some guidance. We have a 3 1/2 ton Bryant Heat pump model 697CNX042000AAA in our home. I noticed two weeks ago that it was frozen up. We're talking 1" plus of ice on everything. Called one of the local HVAC places and the tec. told me that the defrost board was bad due to not being able to force it into defrost. Both the board and sensor were changed, but the unit still froze up. When he came back, he still couldn't get it to force defrost. He tested the coolant levels in the system and the pressures were in line with the factory specs. When the unit is switched over to A/C, the reversing value energizes, it switches to cooling mode, and the ice will melt like it was in defrost mode. The tech is baffled. He's waiting on a call back from Bryant, but I can't get past the fact that it won't even force defrost. When the test terminals are jumped across nothing happens regardless of how long you jump them out. (I know there speed up terminals) The fact that it switches over to A/C leads me to believe the coil and reversing value are O.K., right? What would stop the board from allowing a force defrost, or a regular defrost?

Any help would be great, I don't want to get screwed by replacing a unit that can be fixed.

Joe

[JoeMcG]

I spoke to the Tech. on the phone last night...He talked to Bryant, but they didn't really have anything to add to the cause. He "thinks" the reversing value is sticking since the inlet side of the value for heating started to frost up a bit when he was here last time and the unit does what it's supposed to when in A/C. When I asked him why that would stop a force defrost, he didn't have an answer. My thinking is, If it switches over during A/C then it should go into defrost. If it was sticking on the heating side then it wouldn't heat as well, correct? But it does. It just seems to me that's it's electrical. Is there anything electrical that I can check? There pushing me to put in a new unit but I"m still not convinced that it's not something simple. I guess the new board could have been bad, but that's the second one I've had in it. Any suggestions? I'm at wits end, and I've learned way more about heat pumps than I ever wanted to...

[JoeMcG]

Well, I believe I fixed it. It was not the reversing value as the Tech. insisted, but an electrical issue at the circuit board. Eric, one of the engineers from ICM controls, who I bought the circuit board from, walked me through trouble shooting the board and I was able to find the problem. Could have sworn that's what I paid the HVAC company for. The tech dropped off estimates for new heat pump systems today while I was at work. He felt it wasn't worth fixing the heat pump since it was so old, installed in '93.

[JoeMcG]

Oh yeah, can't wait to call the tech in the morning.

[Home Wrecker]

Well, I believe I fixed it. It was not the reversing value as the Tech. insisted, but an electrical issue at the circuit board. Eric, one of the engineers from ICM controls, who I bought the circuit board from, walked me through trouble shooting the board and I was able to find the problem.

So what was the issue at the board? Something you were able to fix locally, or did you have to put in yet another replacement board?

I've got a Bryant unit of similar age and I'm dreading the day the controls go belly up...

[JoeMcG]

There was nothing wrong with the new board or the old board, it was an issue with the wires that attached to the board. Two of the connections on the wires were bad, but you couldn't see them because they were covered with a plastic shroud. I found it when I was checking voltage to the terminals while troubleshooting the board with ICM. Replaced the connections, which took all of 5 min., and everything tested out the way it was supposed to.

As far as changing the board and DFT, it only took about 15 min. It's really easy to do. The HVAC company was going to charge me $500 to do it, but I did it for $194. I bought the parts from bestbuyheatingandairconditioning.com. The board comes with pretty good wiring diagram so you don't wire it wrong.

Joe

[Home Wrecker]

Excellent that you were able to find and fix that problem yourself. I'm certainly no heat pump expert, but I can answer one of your original questions...

"The fact that it switches over to A/C leads me to believe the coil and reversing [valve] are O.K., right?"

Right. (Obviously too late now, but right. )

Let's see... On my end, in the past three years, I've already replaced the main power contactor in the outdoor unit one year (which had welded itself closed in the middle of a summer A/C session), the compressor the next year (which I now suspect took damage when the contactor stuck shut), and the next year, the fan in the indoor air handler unit. I've not yet had trouble with any of the control boards, but I'm just waiting... I suspect it's inevitable.

Thanks for the tip on where to get the control boards. I was figuring that would be a last straw for me, but if one of mine fails and it's cheap enough, I may continue to throw good money after bad. I suspect that a new unit will be more efficient than my old one, and it might be a better idea to replace the entire system.

I'm in the same position as you... "I've learned way more about heat pumps than I ever wanted to..."

[JoeMcG]

If you replace the defrost board replace the dft as well. Total for mine with shipping was $194.

I agree with you, there gets a point where it is just best to replace the unit(s), but with mine, I knew it wasn't the reversing value. I called the company Thursday morning and told the secretary the whole story. She said she would talk to the owner about getting me the money for the service call back, but I'm not going to hold my breath. It's a shame, if they gave me back the money I paid for the service call that would tell me they cared about the customer and I'd have no problem calling them again, but not now. Satisfy a customer and he tells 5 people. Screw one over and he tells 50.

[Home Wrecker]

Yeah, that's a tough call about getting a refund for the service call.

Their side is that they spent time in thier truck, burned their gas, and paid thier employees while working on your heater. End of story.

Your side is "Well, if they sent someone who really knew what they were doing, they would have diagnosed the true underlying problem the first time I would not have spent an unnecessary $200 to replace parts that were never the problem in the first place."

And so on... Yuk. I wish you well, however it turns out.

[JoeMcG]

Right...it's not worth any more of my time or energy. Thanks for help.