Hvac help

noway2

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Thought I would post the question and see if anyone has any suggestions.

~15 year old Tempstar heat pump quit cooling suddenly. Contactor not engaging, causing neither condenser fan or compressor to run. Depress plunger and they start. Relays "click" when unit is commended on, meaning it is getting the 24 volts. Contactor works if you apply 24 volts.

My guess is an issue with the circuit board. Any thoughts or suggestions? Would rather not replace it but I would get an R410 machine before dumping a bunch of money into an old R22 machine.
 
To give you some perspective. Ours were original, two 25yo units. On average I was spending $300-400/yr to maintain them where they could cool.

Decided to rip and replace with "better" units (heat and air). Looking at the the total cost vs the maintenance and energy sayings I'm only paying $50/mo extra. Plus the house is cooler, less dust and a piece of mind due to a 7 year warranty. I figure after 4 years that extra $50 will be well spent.
 
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Does the 24 volts go through safeties? Does this machine have a manual reset high pressure switch?
 
Did you check to see if the condensate drain for your air handler is clogged up? If it is - or if the condensate pump goes out, it can prevent the condenser from starting.
 
there may be a loss of charge (low pressure ) switch. take a cap off of the valve and use something pointed to depress the shrader core to see if there is any pressure . may have developed a leak and lost the charge. the loss of charge switch is designed to keep the compressor from running with an empty system
 
Update. With some help from Jack Daniels (a friend, not the booze) we put it back together. Turned it on without the 240vac and the contact pulled in. Head scratch. Turned it off, turned it on and waited for the time out, it kicked on and started both fan and compressor. As of now it’s cooling down. Best guess is corrosion on a contact or cold solder joint got moved.

Does the 24 volts go through safeties? Does this machine have a manual reset high pressure switch?
Don’t know if it has a manual or automatic switch. We tried measuring the 24v. The wiring diagram shows it coming off one of the P&B relays, which doesn’t make sense unless they’re obfuscating the circuit. Weren’t able to read it on the second set of posts but it pulled in the contact.
Did you check to see if the condensate drain for your air handler is clogged up? If it is - or if the condensate pump goes out, it can prevent the condenser from starting.
Shouldn't be clogged. It clogged once before and overflowed to the pan which drains on to the deck in front of the kitchen window. That won’t shut it down.

there may be a loss of charge (low pressure ) switch. take a cap off of the valve and use something pointed to depress the shrader core to see if there is any pressure . may have developed a leak and lost the charge. the loss of charge switch is designed to keep the compressor from running with an empty system
I had issues with this one having a slow leak. After it got serviced last time, they put pipe dope and a metal cap on the low side Schrader valve. I haven’t had to add any gas in a couple of seasons. It was keeping up fine until it spontaneously quit.

The only oddity that I noticed briefly was when I thought I turned it on the thermostat displayed 73 which would be the heat set point, not the ambient or cooling set point, but I can’t say for sure. I wonder if it screwed up and went to heat mode or something?
 
My unit quit last week (York A/C only added to existing furnace in 90's) and the condenser fan and compresses not running, but air handler fan was running. Motor start capacitor in condenser had failed, and it apparently provides start delay for both motors.
 
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Fried bugs in one side of the contractor not allowing line voltage to pass to motors. Change contactor. Spray the electrical compartment with bug spray every year and place one moth ball on the electrical compartment ledge.

To change contractor turn off both the air handler and condenser breakers. Verify with a meter no power is present. Take a picture of the wiring and label each wire with a number from a electrical wire label sticky sheet. Change the contactor and reattached the wires being careful to put them in the same place. Put the cover back on and turn both breakers back on.

Contactor points are low quality Chinese with low silver content now. They should be replaced every three years before they get pitted and arc weld together. I had a guy tell me his got stuck and his power bill was $700.00 in July. Small price for a service call for having a normal power bill and not ruining a compressor.
 
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Change contactor. Spray the electrical compartment with bug spray every year and place one mouth ball on the electrical compartment ledge.
Funny that you should mention that. On the ground near one of the units we found a mothball. We were wondering where it came from.

Oh, and take two or three pictures. I took one before removing the contactor but some of the wires were hidden. Fortunately between the picture and the wiring diagram I was able to get it all back.
 
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