Heat Pump does not start

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Old 01-04-14, 10:25 AM
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Heat Pump does not start

Hello,
I have a 2 years old, self-contained, 5 ton, Goodman heat pump (gpc/gph13 series) that does not heat.

I opened the panel where all the electrical components are located, checked if there was voltage at the contactor, and I only found the 240 volt at one side of the contactor, but zero volts at the contactor coil.

The transformer readings were 240 volts on the primary and 26 volts on the secondary.

This was done with the inside thermostat set on heat and at 70 degrees, while the outside temperature was 34 degrees and the inside temperature reading on the thermostat was 57 degrees.

There's any way I could bypass the control board operation or close manually a circuit, in order to feed the 24 volts to the contactor coil just to check if the compressor comes up and the pump starts to heat?

How do I troubleshoot the control board?

Any other suggestion will also be greatly appreciated.... and thank you in advance.

alexpio
 
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Old 01-04-14, 10:34 AM
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Alex we must make sure that you are correctly placing the meter leads to check for voltage. It can be confusing on where to place the meter leads to get a correct reading. I would like for you to go back to the contactor and with the meter set to AC 250 or 300 volts range check between the 2 main lugs coming into the contactor and then on the outlet end of the contactor. Nothing to be ashamed of I have seen seasoned techs take false readings at times. Now while you are there on the contactor low voltage coil I want you to take a reading from EACH side back to the C pin on the terminal board. Holler back when you get those readings. I will be around for a few minutes here.
 
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Old 01-04-14, 11:27 AM
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voltage readings

ok,

here's my readings:

T1 - T2 = 0 volts

L1 - L2 = 245/246 volts

reading between the 2 terminals of contactor coil = 0 volts

reading between upper terminal of contactor coil and C pin = 3 volts

reading between lower terminal of contactor coil and C pin = 1 volts

Thank you buddy
 
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Old 01-04-14, 11:36 AM
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Excellent info thanks for getting back to me. That tells us that main power is good and that we have NO low voltage getting to the contactor so now lets find the terminal board inside the unit where the tstat wires go to and check the following from R to C from Y to C from G to C from W to C Also do you have some alligator clip jumpers per chance?
 
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Old 01-04-14, 12:08 PM
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Here it is:

R - C = 28.2
Y - C = 27.9/28.3
W -C = 27.3


I don't see a G pin, but I see an O pin, a DFT pin and an Rdft and took measurements from those also:

O - C = 1 ----- orange wire here

DFT - C = 27.7
Rdft - C = 27.6
 
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Old 01-04-14, 01:01 PM
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Per those readings the tsat is sending voltage to the terminal board so we have eliminated the tstat and transformer as the problem. Now trace the 24 volt HOT wire from the contactor back and see where it terminates check for 24 to 29 volts to C as you back up and see which device is cutting the power. Note C common side of the contactor low voltage coil will have continuity back to C pin (probably to ground also but some systems are floating so check everything back to C Pin) the other side of the 24 volt contactor coil is the HOT side that is what we want to trace back and start checking for the power loss. If you found your alligator jumers we may be in business here in a few minutes just be sure to remember which side of the contactor coil 24 volt checks out as the HOT side
 
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Old 01-04-14, 02:44 PM
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Not sure if I understood it correctly, but here is what I did:

First of all, there are 2 wires connected at each terminal of the contactor coil.

On the upper terminal, one wire comes from the 24 volt transformer, and the other goes down to the inside thermostat.

On the lower terminal, one wire goes to the fan blower, and the other goes to the CNT pin on the board.

With the tester set at 20KOhm, the reading from both the terminals to the C pin is zero.

With the tester set at 20 volts, the reading from both the terminals to the C pin is 17.3.

With the tester set at 200 volts, the reading from both the terminals to the terminal of the 24 volt transformer is 27.3.

Again, not sure if this is what you were looking for, but I am in a limbo. What's next?

thanks,
Alex
 
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Old 01-05-14, 02:17 AM
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Alex sorry I have been away from the computer I did not mean to leave you stranded (The unit does heat in emergency heat mode correct?) I suspect that you have a loss of charge safety limit kicked out or a bad board. Here is a link to the actual servicing checks for you unit http://johnstonesupply9.com/TechDocs...vice%20Man.pdf looks like around page 29 or so they mention checking the low charge safety switch. I would not replace the board unless I was sure that it is bad. You seem to be proficient with the meter so just be careful around the HOT wires and follow the instructions and have fun.
 
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Old 01-05-14, 11:50 AM
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Thanks for your help Master.

I've been looking at the troubleshooting table and, I may be wrong, but everything points out to a faulty thermostat or to shorted or broken wires.

The table gives me a scenario that fits my picture, where compressor and condenser fan don't start and all the possible causes:

1) blown fuse ---- I have voltage, so this one is to be excluded.
2) shorted or broken wires ------ this could be one of the possible cause, even I really hope it is NOT.
3) faulty thermostat ------- hope this is it
4) faulty transformer ------to be excluded ---- I have 24 volts on the secondary
5) faulty contactor ------- to be excluded at this stage ----- there's
continuity in the coil but not enough voltage to get it excited.

Now, before I search for other causes, if I want to test the thermostat, can I take the following steps?

1) set the thermostat to heat with the temperature set at 80 degrees, while the inside temperature reading is 65 degrees, go to the electrical panel, unplug the wire from the W pin and check that wire for continuity with the C pin. Should I have a zero reading if the thermostat is working?

2) set the thermostat to cool with the temperature set at 55 degrees, while the inside temperature reading is 65 degrees, go to the electrical panel, unplug the wire from the Y pin and check that wire for continuity with the C pin. Should I have a zero reading if the thermostat is working?

Will this procedure work? I don't have an amprobe to follow the procedure outlined in the troubleshooting table.

Thanks,
alex
 
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Old 01-12-14, 07:50 PM
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About two weeks ago I noticed my ac was not blowing cold air. I noticed the outside unit fan was not spinning. After doing a few hours of web research I decided to change the capacitor. Wa la!! It worked.... For about a week. A couple of days ago I noticed that the problem had returned again! Now nothin is working at all. At least the first time I heard a loud humming and when I used a stick the fan and motor would kick on. Now nothing. Please help!
 
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