Hello,

Working on a new problem with my old carrier heat pump. Recently, it started this problem (while on heat) of clicking once or twice on the thermostat, and then going to wait.

Outside, I checked things out, and after testing the start caps, which was below specs, I ordered a new one. Of course, it didn't fix. I then started looking at the contactor, which I've replaced before. When I opened the unit, the contactor had a lizard that had been electrocuted "action movie style" right across the high voltage contactors at the top. I still don't know if that can break a contactor or not, but anyway, I manually pushed in the contactor and verified that my compressor and fan were still working (had a hot refrigerant pipe).

I've since taken the contactor off twice, broke the corner off of it, and tested the coil which is at about 11ohms, so I think the coil is OK. The problems seems to be that I can't easily test for low voltage at the contactor because of this compressor delay thing that keeps kicking in with my honeywell thermostat. Thing is, the contactor clicks and tried to engage right as the thermostat clicks inside. So, I *think* there may be proper voltage at the contactor , briefly, but something is causing it to short out in some way. What I'm wondering is if the contactor could have a "good" coil , but some other kind of mechanical problem (like the damaged pads I had on the previous), or if this is an issue with the circuit board on the outside unit, or even a thermostat problem.

I'm seeing myself getting confused on this one Thanks much for any ideas!

 

What type of thermostat are we dealing with?
Geo

 

I don't know the exact model, but i'm pretty sure it's a honeywell. Looks like this on the outside. has setback, schedule, etc.

 

Just did some more digging. I forgot this thermostat had battery. They were dead, and completely explode Managed to clean out, put new batteries in, but I'm not sure if things are right, because the thermostat is DEAD until plug into the wall socket with the wiring.

Put the connector back on again, and thought it might work. Still no go. Went out and had meter connected to low voltage at contactor. It appears that no voltage is getting to contactor, and the contactor wasn't what was clicking. Something inside the unit is clicking, and the only thing I know about in there is the reversing valve, which I replaced about 5 years ago. Is that likely what is clicking, and would a short there cause no voltage to reach the contactor?

On a side note, the unit has been running in heat mode (winter) up until this break. I do know from the previous reverse valve failure that the valve is normally in heat mode anyway, and must be energized to move to cool. So, I guess it could be shorted or stuck and unit would still put out heat when forced on manually at the contactor, as it is now.

 

If you have a short the fuse would blow on the furnace control board.

 

I have seen that thermostat click to Wait when a short is present. This occurs fast enough to save the fuse.

I would check the wires to the pressure switches in the outdoor unit for a short.
I would also check the wires to the temperature sensor clamped to a ubend on the outdoor coil.

If you do not see a spot that has rubbed through the wire insulation causing a short between the lo voltage wire and a copper pipe or the body of the outdoor unit, remove and isolate the Y wire to the outdoor unit at the heat pump and give the thermostat a heating demand to prove if the short is outside.

 

I don't have much experience in the HVAC field,

 

thanks houston, but i'm not sure i understand your troubleshooting steps. How do I "remove" or isolate that wire? Also, any idea what's clicking inside the outdoor unit?

I think I incorrectly stated that I had replaced the reversing valve on this unit. I think what was actually replaced before was the reversing valve solenoid. Incidentally, this solenoid was causing a clicking inside the unit, as I'm hearing now.

 

Take off the orange wire nut that connects the stat wire to the heat pump Y wire outside to isolate Y.

The reversing valve should not have 24 volts to it in heat mode. It gets 24 volts in cool mode.

 

So the Y wire should have 24v when heat is engaged?

I can check that tomorrow.

What I meant by the clicking, is that it happens the same in heat and cool mode. I was confused by that, because in heat mode, I would think the reversing valve wouldn't get any power at all, yet something is still clicking in there in both cool and heat.

 

Thanks Houston. I checked across the Y and B and had the 24 volts, and t-stat stayed on.

Well, I'm thinking my hunch on the reversing valve was correct. With the reversing valve coil unplugged, the unit works in heat mode.

Removed coil, and it tests at about 17OHMS. Is this a stuck valve or a possible bad coil?

 

17 ohms is a good reading for a reversing valve coil.
I have seen 3 ohms cause the Wait error.

What does the wiring to the solenoid look like?
Are you sure that you have a Carrier?
Do you have 24 volts across the 2 leads to the reversing valve?
Is thermostat function 190 set to 0 or 1?

 

The wiring to the solenoid looks OK. Two brown wires going to the plug. The wire has always been tight as it feeds up into the electrical panel on the outside unit.

When I test voltage , I'm getting about 10 volts to the solenoid plug (while in heat mode), which doesn't make sense to me. Could that be the sign of a faulty defrost board?

Yes, of course I'm sure it's a Carrier. This is my home unit, and I've been fixing it for 10 years now

On the thermostat, I checked and it is a TH8000 series. I don't see the option for the 190, or anything like that in advanced settings on this one, but maybe I missed something?

 

just checked in cool mode, and there is 24 volts. so it's reading 10 volts to solenoid in heat, and 24 in cool, but when it's connected, the reversing valve just makes a single clicking noise, and the contactor never energizes. thermostat goes to "wait".

stuck reversing valve? i'm not sure on that, because as i understand it, the system won't "know" anything about the condition of the reversing valve, as it's just energizing that coil. is that correct?

 

It sounds like something may be wrong with the defrost timer board. Do you have 0 volts between O and C outside when a demand for heat is present?
Is 10 volts still present when you disconnect O to the heat pump at the outdoor control wire connections?


If you hit System to clear the bottom buttons and hold the buttons on either side if the center button you will enter the advanced installer functions. The center button only enters a limited function homeowner menu.
It sounds like 190 is correctly configured.

 

Thanks Houston. It's getting tougher to debug this problem outside.

In short, I'm getting voltage all over out there, even with thermostat completely unplugged from wall.

When I isolated and checked blue/orange, I got kind of the same results as down at the reversing valve. 10 volt in heat, and about 27 in cool.

It appears that the reversing valve never stops getting power (enough to get burning hot) unless it is physically unplugged now. I also had 27 volts at the yellow wire, even with the system set to "off" on the thermostat, which I'm confused about, because the system seemed to be shutting off OK.

I'm wondering if I have a transformer or short issue inside the air handler.

 

I think I should check voltage at the leads going to the wall socket for the thermostat, but I am not sure what those voltages should be.

 

If you disconnect O outside at the heat pump you can eliminate the stat, the air handler and the control wire between the stat and the air handler as well as the control wire between the air handler and the heat pump as the cause of this problem.

 

OK, disco'd and isolated O at the heat pump. Connected rev valve coil, and all other connections. Same as expected. Unit runs in (default) heat mode, and I have about 10 volts at O from the wire going inside.

Also, checked thermostat socket with O and B disco'd outside. 27v on R, 4-5v on Y and O.

forgot to add, with O disconnected at heat pump, there is no voltage at the reversing valve coil while in heat mode ... but with O connected, I believe there is currently always voltage. either 10 or 24+

 

You have proven it isn't the defrost timer.
I would isolate and test at the air handler next.


R = 24 volt power
C = 24 volt common
Y = compressor
G = fan
Aux = heat strip
E = heat strip (may be Aux/E)
O = reversing valve

R to C should read 24 volts AC
every other terminal should read 0 volts to C when the stat is removed and you measure the terminals on the subbase.

 

yeah, I tested the sub base earlier, and it's doesn't appear right...

"Also, checked thermostat socket with O and B disco'd outside. 27v on R, 4-5v on Y and O."

 

Do you have 10 volts between O and C at the subbase?
If it is present it proves the problem isn't the stat.


Is O connected to the air handler?
What is the air handler model number if O is connected to it?
Do you have any unused control wires that you can sub for orange? (like blue)

 

What I typed just before. It's 4-5 volts for O and Y at the stat base (stat unplugged). When connected out at the heat pump, it becomes 10 volts or more. I agree, that it seems something is definitely wrong in the air handler .. but I'm not sure how to figure out what. Had the cover off. Will take a picture and check the model.

 

Is that measuring Y to O or O to C?
We want to measure O to C.

 

Pretty sure I measure all points to common. At least that's what I was trying to do I'll check again. Also, getting picture of air handler.

I can see the O wire going in to handler, but not sure if/how it connects to anything.

 

OK. Good thing I checked the sub base again. All is OK there, except for O. Still have 3-4V from O to C at the sub base.

Here is the model info, wiring diag for handler, and picture of handler.

 

It doesn't connect to that air handler board but it can short to the air handler body...

 

Just wanted to follow up and say thanks again Houston.

Strangely, the problem just went away, and in the end I did nothing besides replace the run capacitor on the compressor - which I think was needless anyway.

I'm not sure if a very small crack in wire casing or what, but it seems just pulling things apart, losing a few screws, and putting it back together, resolved that short. I guess it may return, and surely if it does, it will be at a bad time.