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sully2 08-14-2011 10:49 AM

Lennox Heat Pump shuts down
Iím having problem with a 1996 Lennox heat pump Hp 026-037-7p
I believe the current problem was brought by the condenser fan
Going out over several weeks, and the unit getting to hot and short
cycling too many times. The condenser fan and coil have been replaced.
The air handler was replaced 1.5 years ago, itís a APH made by York.

At this point, the System will run for several hours (7-20) then shuts down.
The contactor will be in the run position, but the fan and compressor will not run.
The circuit board has two lights that blink steady, indicating ďnormal operationí
The condenser fan will occasionally kick on and off during this shut down phase.
My neighbor let me use his gauges to see whatís happening during shut down.
I monitored the gauges every half hour and found them to be steady at 65/200
while the system is running.
When the unit shut down the gauges went to 125/160 after a half hour, 150/160.

When the unit shut down, I turned the thermostat to the off position, and give it 1-2
Hours to cool down. After an hour I re-start and found the gauges to be 55/180.
Ive taped a cooking thermometer to the top of the compressor and found it to be running at a consistent 165 degrees F.

Any thoughts?

Master of Cold 08-14-2011 02:02 PM

Well first off your low on charge. Which will trip the thermal overload in the compressor. The fan not running is an indication of a defrost board problem.
You can take the black wire out of the relay (the thicker one) and put it on the top of the contactor, with the other black wires. This will bypass the relay and let the fan run.
You ned to have someone come out and find the leak, or at least charge it back up.

beenthere 08-15-2011 04:31 AM

Is the condenser fan spinning backwards?

sully2 08-15-2011 05:48 AM

the fan is shooting the air up wards out of the condensing unit.
My neighbor who supposedly does ac work for a living looked at the gauges and said the charge is good. I just looked at the chart on the inner panel, and it says for r22 the hp036 should be 78 on the suction side. is 65 low enough to cause it to keep shutting down?

The unit always trips off around 3-4 am when the ambient outdoor temp gets close to 78 where the thermstat is set. like it wont come back on after it cycles off.

last night I found one of the 2 thermals overload sensors was a closed circuit. the sensor looks a bit warn out. I unhooked it from the board where it was plugged into "OF" and "PF". I'll replace that in the morning.

@Master- the condensor fan runs whenever the compressor decides to run. I'd rather not bypass the contactor. Thanks Guys

beenthere 08-15-2011 04:04 PM

How hot was it outside and inside when he checked the pressure. SH and SC would tell whats going on with the charge, pressure doesn't tell you much.

Doc Holliday 08-15-2011 06:43 PM

I have the same problem on the same Lennox. The board in the condenser led one is solid meaning board failure. I have pi
cs ill post in a bit.

Doc Holliday 08-15-2011 06:47 PM

It has call to board and 240volts but not coming on.

Marty S. 08-15-2011 06:59 PM

Doc the only thing between the board and contactor is a high pressure switch. Double check the code because one solid and one off is also a high pressure lock out signal. Pull R from the board for a few seconds to reset the lock out.

Doc Holliday 08-15-2011 07:39 PM

Tunis Marty. I saw the legend and that was what it coded, led one solid meaning control board. Failure. So that's what i diagnosed it as.
I'm not familiar with heat pumps. Ill post the pic i took. Of the board with solid. Led one and legend when i get home.
Thanks Marty.

Doc Holliday 08-15-2011 07:40 PM

Tunis? Too funny! Thanks.

Master of Cold 08-15-2011 07:44 PM

There is a low pressure, and high pressure option on the board. Switch may or may not be there depending on the unit.

Master of Cold 08-15-2011 07:46 PM

Also..lennox residential boards have a terrible failure rate. Try grabbing the terminal block and twisting it.

Doc Holliday 08-15-2011 09:09 PM

Doc Holliday 08-15-2011 09:11 PM

Led on left is one: legend which might be unlegible states led one (or two) solid board failure.

Doc Holliday 08-15-2011 09:24 PM

And as you can see there is nothing between the call and the board. The call goes straight to and through the board and comes out the other side. There might be a pressure switch between the board and the high voltage fan/compressor "on", but I'm not sure.

Thanks guys, I can certainly use the help.

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