Heat Pump Not Turning On

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Old 11-15-15, 06:47 AM
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Heat Pump Not Turning On

As of this morning, my heat pump is working. I did a visual inspection and there are no burnt or disconnected wires, no bulging capacitors, and there is 240V present. The heat pump isn't making any buzzing or clicking noises. I'm wondering if the issue is with the thermostat. I can hear the relays click when I turn the heat on. What are some tests I can do to isolate the issue? The heat pump is a Goodman and the thermostat is a 3M filtrete programmable unit with C, O, W2, Y, RH, RC, and G wires (RH AND RC jumpered). Five wire electric heat pump with auxiliary heat. Indoor unit (air handler) is a two year old Goodman ARUF 2-1/2 ton. Outdoor unit is 12 years old BTW. And last night was the coldest night of the year so kind of ironic. Can I short a couple terminals together at the thermostat to see if the heat pump then turns on? I'm getting 27Vac on G, RH/RC, and Y. No voltage on any other wires. According to the manual, Y is "cool control", so I'm not sure why it has voltage. Y has 27V regardless if in heat or cool mode. Heat pump doesn't turn on in cool mode either and there is no voltage on RH/RC when the thermostat is off.
 

Last edited by mossman; 11-15-15 at 07:15 AM.
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Old 11-15-15, 07:38 AM
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After poking and prodding and a power cycle, the heat pump is alive again. So I'm good for now, but have no clue what the issue was. Perhaps the control board was stuck in some protection mode or something? Guess I better start budgeting for a new one. I'm surprised it has lasted this long.
 
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Old 11-15-15, 09:31 AM
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The Y terminal is the compressor line so it should be active in the summer and winter. Anytime the compressor needs to run. In order for the condensor to know whether it's in the cool or heat mode.... power is applied to the orange wire to activate the reversing valve in cooling mode.

If you had power on the Y terminal.... the compressor should have been running. There is a board in the condensor that controls defrost. That board could keep the compressor from running.
You could also be low on refrigerant. That would also keep the compressor from running.

You may need to check out the contactor in the condensor to see if it's getting worn or burned.
 

Last edited by PJmax; 11-15-15 at 03:10 PM. Reason: typo
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Old 11-15-15, 01:20 PM
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I had voltage on both sides of the contactor, but 120V on all three capacitor leads, which doesn't seem right. How can I check if the heat pump is not on because of low refrigerant, other than having the charge checked? Wouldn't my coil freeze up if I had a leak or does that only happen in cooling mode?
 

Last edited by mossman; 11-15-15 at 01:42 PM.
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Old 11-15-15, 03:12 PM
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If your contactor was closed you would be ok on refrigerant.


Did you have 240vac across the incoming and outgoing terminals on the contactor ?
 
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Old 11-15-15, 07:11 PM
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I measured from ground to each contact and all of them had 120V, so yes.
 
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Old 11-15-15, 07:29 PM
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If you have only 1 leg of power to the unit you can still measure 120 volts to ground on L1 to ground and L2 to ground because of backfeeding.

The correct test to prove 240 volts is to measure for 240 volts between L1 and L2.
 
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Old 11-16-15, 05:20 AM
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Okay. I'll measure again. Heat pump worked all night but is not working again this morning. Since the past two nights have been the coldest this season, I'm thinking it has to be something sensitive to temperature change, such as a faulty switch or maybe a bad solder joint on the control board. If I dont have 240 across the contactor switch, what is the best way to test if the switch is the issue or if the signal controlling the switch is the issue? I'll post photos shortly.
 
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Old 11-16-15, 05:55 AM
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Okay. I had no voltage on the downstream side of the contactor switch and could clearly see that the switch was open. I used a plastic screwdriver and pressed the contact inward and the unit turned on until I let go. I then jumpered the R wire on the control board to the Y wire and the switch closed/unit turned on. It is running as I type this but it will surely fail again. So apparently the switch is fine and I now suspect the control circuitry. What voltages should. Be seeing in the control wires coming into the unit and out of the control board? I have 27Vac on the R wire and measured 15Vac on the yellow coming off the control board with respect to ground.
 
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Old 11-16-15, 07:17 AM
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Here are a few photos of my unit. Does the fact that I can tap power to the yellow wire and the until remains on isolate the problem at all? While awaiting additional feedback, I may clean all the connections with contact cleaner, replace the wire nuts, and reflow the solder joints on the control board just to be sure everything has a good connection. I've seen several defrost control boards online for under $50, so I may just replace the board.

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Last edited by mossman; 11-16-15 at 07:47 AM.
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Old 11-16-15, 07:48 AM
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There is a board in the condensor that controls defrost. That board could keep the compressor from running.
What test(s) can I do to see if the defrost board is keeping the contactor switch from closing?

I found a Q&A session online describing the same issue I am having. I'm going to check my unit per this conversation and see if I can isolate the problem. The technician says to check for continuity of the pressure switch. He says to check between the purple wire on the board and the yellow wire to be sure they are connected/shorted. However, I believe the purple wire goes to the condensor fan??? There are no other purple wires.

http://www.justanswer.com/hvac/46vnn...html#re.v/327/

To reiterate, once I get the heat pump running, it blows very warm air and runs fine all day. It is only at nighttime after the outside temperature drops into the 30's and 40's that it will not turn back on. Daytime temps have been in the mid to upper 60's.
 

Last edited by mossman; 11-16-15 at 09:52 AM.
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Old 11-16-15, 10:25 AM
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I have 27Vac on the R wire and measured 15Vac on the yellow coming off the control board with respect to ground.
Did you measure voltages to ground ? Usually the C terminal is used for voltage measurements as the C terminal is not always ground.

The 15vac on the Y terminal is coming from the thermostat.

When the unit is calling for heat or cool..... the Y voltage (24v) is sent from the stat to the air handler. At the air handler it connects with Y wire going outside to the condensor. It needs to be 24vac everywhere it's checked.
 
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Old 11-16-15, 10:42 AM
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I believe I found a schematic very similar to my unit. This will help me with troubleshooting. I went ahead and ordered a new control board and contactor so I have them on-hand if needed.
 
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Last edited by mossman; 11-16-15 at 10:57 AM.
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Old 11-16-15, 11:01 AM
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Did you measure voltages to ground ? Usually the C terminal is used for voltage measurements as the C terminal is not always ground.

The 15vac on the Y terminal is coming from the thermostat.

When the unit is calling for heat or cool..... the Y voltage (24v) is sent from the stat to the air handler. At the air handler it connects with Y wire going outside to the condensor. It needs to be 24vac everywhere it's checked.
I realize now that I should be measuring between common/C (blue wire) to get the proper voltages. I seem to remember getting only a couple volts when probing between Y and C. The diagram I found shows a low pressure switch in series with the yellow wire, but I believe my yellow wire is connected directly to Y on the control board. I'll have to check again this evening when I get home.
 
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Old 11-16-15, 11:05 AM
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You need to measure the Y wire at the air handler.
Then measure is where it connects to the condensor.... before any safeties..... measure it right at the wirenuts or screw connections.

You need to diagnose whether the problem is inside or out.
 
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Old 11-16-15, 11:12 AM
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I measured 27V on the yellow wire at the air handler (actually measured across the transformer output -- blue and yellow wires). I will check for 27V on the yellow wire at the incoming connection to the heat pump when I get home this evening. If I have 27V, then I know my issue is with the heat pump control board. If not, then a break in the wire from the air handler to the heat pump. Air handler is only two years old and the wiring is 30 years old.
 

Last edited by mossman; 11-16-15 at 11:38 AM.
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Old 11-16-15, 07:06 PM
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I likely won't be able to look at it again until Wednesday, but the heat pump is still operational so no biggie. I've been studying the wiring diagram and watching a few videos in the functionality of defrost boards and if I understand correctly, the defrost board would not keep the contactor and compressor from turning on. When there is 24V on the yellow compressor wire, the fan and the compressor should turn on. Also, it looks like I actually do have a low pressure switch in series with the yellow wire. That being said, it seems to me that I either have low pressure (don't think I do...duct air is very warm) or an issue with the wiring, either a corroded connection or broken wire. Do you guys agree that if the yellow wire has 24V, that at least the compressor should be on regardless if the defrost board is faulty? I suppose the low pressure switch itself could be bad. That should be easy to test. If so, I'll just bypass it (I'm assuming the system would need to be evacuated and recharged if I remove and replace it with a new one?).
 
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Old 11-16-15, 07:21 PM
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After looking at my photos again, it appears that the yellow wire from the t-stat is connected directly to the contactor coil. I definitely have some sort of sensor on the high pressure freon line with two yellow wires leading into the control area, but I don't think they are connected to anything. I'll stop rambling until I hear back from someone or have more definitive information to share.
 
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Old 11-16-15, 08:57 PM
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As long as the yellow wire has power.....the contactor should be closed.

The defrost board does several things.....
1) it turns off power to the reversing valve which turns the heat pump back into an air conditioner. The system now uses inside heat to unthaw the outside coils.
2) it turns off or cycle the condensor fan during defrost mode.
3) it turns on the electric reheat coils inside the air handler so the house doesn't get too cold during defrost.

You said the compressor wasn't running when it gets real cold. That could mean that the system is low on refrigerant which would interrupt power to the contactor. The pressure switch is supposed to be in the yellow line to the contactor.

You may need to have the refrigerant level checked.
 
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Old 11-17-15, 04:29 AM
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I isolated the problem. The heat pump stopped running sometime last night again, so I went out this morning to take another look. I had 27V on the yellow wire coming into the unit, but nothing across the contactor coil. Turns out the low pressure switch IS connected. The wires are all bundled up so it was hard to see what was going where. As a temporary solution, I bypassed the LPS. How sensitive are these switches? Do they get more sensitive or even fail after a while? Reason I ask is because my duct air is very warm, almost too warm (no, the heating coils are not coming on). How low would I need to be on freon before I would notice it? And what potential is there for damage by bypassing the sensor? I imagine if the pressure got low enough that it would damage the compressor due to lack of lubrication. Everything sounds fine and is heating great so my guess is either the switch is overly sensitive or faulty. What do you guys think? And am I correct by assuming the system would need recharging if I removed and replaced the LPS?

Oh, and the wiring diagram is on the inside if the controls cover. Should have known to check there!
 
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Old 11-17-15, 06:52 AM
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Let me recap for those overwhelmed with details:

My Goodman CPLE30-1C heat pump stopped working completely (no compressor, no fan) as of two days ago. I determined the low pressure switch is not closing and thus 27V is not being applied to the contactor relay coil. I temporarily jumped 27V from the red wire to the yellow (feeding positive side of contactor relay coil) and the unit came on and stayed on. It cycled several times throughout the day no problem, but shut off again sometime during the night. This morning, I bypassed the low pressure switch and the heat pump is running again. Duct air is nice and warm, compressor sounds good, no visible or audible leaks.

My outstanding questions are as follows:

- If the system is low on freon, will the low pressure sensor be able to detect this while the compressor is running? Or can it only detect low pressure while the system is off?

- Is the system pressure slightly lower when the ambient temperature is cooler? Higher when warmer? I ask this because it has been cooler the past couple of nights.

- Since I was able to get the heat pump running by momentarily connecting 27V to the contactor coil, the low pressure switch obviously closed upon me doing so (because the heat pump continued to run). Does this mean the low pressure switch is faulty or is it closing because the compressor is running and the system is now under increased pressure?

- How low does the freon need to be before it has a noticeable affect on heating?

- Is it common for low pressure switches to fail after several years or become more sensitive? My unit is 12 years old.

- Can I replace the low pressure sensor without evacuating and recharging the system?

- Is there any harm in bypassing the low pressure sensor if there isn't actually a leak in the system? This would only be temporary until I either replace the sensor or replace the unit. I planned on replacing the unit eventually anyhow, so I'm not overly concerned if the compressor craps out. However, I'd like to get a few more months out of it.

- If there is a leak in the system and this is what is causing the low pressure switch to open, how long until my system would be entirely depleted of charge? Hours? Days?
 

Last edited by mossman; 11-17-15 at 07:08 AM.
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Old 11-17-15, 09:58 AM
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As the ambient air temperature goes down..... so does the system pressure. Once the system is running the heat generated may keep the low pressure side high enough to keep the switch satisfied. Once the system shuts down and the pressure drops..... it drops below the threshold set by the low pressure switch.

No... you do not remove the low pressure switch.
Do low pressure switches go bad.... yes... but very rarely.
If you bypass it you run the risk of seizing the compressor.

Now way for us to know the extent of your leak.
As mentioned previously..... you need to get refrigerant level checked.
 
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Old 11-17-15, 11:07 AM
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No... you do not remove the low pressure switch.
I'm not sure which question you are referencing. Can you rephrase please? Are you telling me to not remove the pressure switch? Don't bypass it? Check the pressure first then replace if necessary?
 
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Old 11-17-15, 11:09 AM
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Yes...... don't bypass it unless you don't care what happens to the compressor.
 
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Old 11-17-15, 11:11 AM
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Gotcha. I'm not overly concerned at this point. If I notice a decrease in air temperature, then I'll think about maybe having it leak checked, charged, or maybe just replaced.
 
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Old 11-17-15, 11:16 AM
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A buddy of mine said he has a gauge with short hose on it that I can borrow to measure the pressure on the liquid line. I found an R-22 temperature/pressure chart. Is determining the correct pressure pretty straightforward as long as I know the freon temp?
 
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Old 11-17-15, 06:24 PM
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Sorry.... according to DIY policy... I can't discuss any problems or questions directly related to system pressures.
 
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Old 11-18-15, 04:32 PM
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Rather than trying to figure out and measure the correct pressure, I'd like to determine what the threshold pressure is of the low pressure switch. That way I can monitor the switch position while observing the pressure. This will tell me if the switch is working properly. I'm having difficulty finding what the psi of my switch is though. It's a Goodman 594511/ B1360719. Anyone know? Maybe it's printed on the switch?
 
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Old 11-18-15, 09:15 PM
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From the Goodman service manual.......

The low pressure control senses the pressure in the suction line and will open its contacts on a drop in pressure. The low pressure control will automatically reset itself with a rise in pressure. The low pressure control is designed to cut-out (open) at approximately 50 PSIG. It will automatically cut-in (close) at approximately 85 PSIG. Test for continuity using a VOM and if not as above, replace
 
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Old 11-19-15, 04:06 AM
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Thanks. I was thinking the sensor was on the high side/liquid line. Regardless, I'll see what I have. Won't be able to look at it until Saturday.
 
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Old 11-20-15, 01:31 PM
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I had a similar issue with the high pressure switch in my York heat pump.
I jumpered around it to keep things running.
With the HPressure switch leads isolated, I put an ohmeter (analogue preferred because it's much quicker) across the leads and then manipulated / jiggled the lead wires ... to discover that there was a break in the wire where it entered the switch potting.
It was very expensive to have the switch replaced because it is brazed in the line, so the evacuate / purge / weigh in routine had to be done besides a fair bit of dis-assembly to expose the switch for brazing.

So, bad engineering for the replacement ease, and curses for the choice of such low quality components .

Just in case your LPS is the same kind of imported junk....
 
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Old 11-20-15, 02:31 PM
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Not sure if it's brazed in or not. This is the one I have:Goodman B1360719 Low Pressure Switch.

I just fiddled with it for a couple minutes...I connected my meter across the sensor and got about 500 ohms. Then I momentarily pressed the contactor switch to allow the heat pump to run for about three seconds. Upon doing so, the pressure switch closed immediately (meter read zero ohms). When the heat pump turned off, the pressure switch stayed close for about a minute, after which I got about 25 to 50 ohms, then eventually an open circuit. Next, I put a gauge in the suction side and read 100 psig. Then I put the gauge on the liquid side and also read 100 psig. So at 100 psig, the switch was open, which tells me the switch is bad. I'm still confused as to why the low pressure switch is on the liquid line (smaller of the two). Isn't the liquid line the high pressure side? It is the only pressure sensor present and has two yellow wires going to it, which according to the schematic is the LPS that is in series with the contactor relay.
 
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Old 11-22-15, 01:44 PM
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I connected a gauge to the low side then the high side while the unit was running, and I got 220 psig on both sides. This is with an ambient temp of 45, indoor temp of 70 and the unit had been running for five minutes. The gauge I am using has a leak in it so I'm sure the actual pressures are higher, but is it normal for the low/suction side to be so high? I expected it to be less than 100 psig.
 
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Old 11-22-15, 02:36 PM
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If the pressure switch is on the small copper line it's a high pressure. But remember, in heat mode the large copper is the high side and the smaller line is the low side.
 
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Old 11-22-15, 03:01 PM
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That's what's confusing...the pressure switch is on the smaller/liquid line and the wiring diagram calls it a low pressure switch ("LPS").
 
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Old 11-22-15, 04:31 PM
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We're treading on thin ice here.... the admins of the DIY board do not allow us to discuss issues pertaining to refrigerant charging and pressures as those are matters handled by an EPA licensed technician.
 
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