Fan And Compressor Not Coming On. Blower Comes On - Hot Air Comes Out Vent HELP!

Good Day. Its a hot day here in Florida, especially on the bottom floor of my home.

I'll preface my explanation of my A/C problem by listing the various parts I've replaced up until this point:

- Defrost Control Board (in heat pump - see pic)
- Contactor Relay
- Capacitor
- Replaced 5 amp fuse in Fan Control Board (in Air Handler)
- Transformer
- To test the T-Stat I took the one on the bottom floor and replace the second floor t-stat(T-Stat appears to be functioning)

Here is my A/C problem:

The motor/blower in the air handler inside the house turns on and air is blowing out the vents (hot air) when the thermostat is set to cool.

The outside unit (heat pump) fan is not kicking on and the compressor does not run until I manually press the contactor button.

When checking for voltage at the contactor I get 240VAC in and 240VAC across the contactor to the compressor.

When I press the contactor button the fan/compressor kicks on, at this point when I check for voltage across the contactor between the 24VAC leads I get 0 VAC. Seems to indicate something on the 24vac side is bad, not the 240vac???

Here is a manual that has a wiring diagram which looks similar to my system (I could not find the wiring diagram for my exact make/model Tempstar/tch236akd1):
http://icpindexing.toddsit.com/docum...2123320101.pdf

I tested the contactor with the help of similar videos like this:
AC not starting up - Air Conditioner condensing unit lost power - Replace Contact contactor relay - YouTube (Preview)

Does this appear to be an issue with the defrost control board? Perhaps its not relaying the 24vac signal to contactor or is there another direction I should be taking to troubleshoot this issue?

 

A few more of them and you might have a appetizer.

 

This is the second time that has happen with a frog committing suicide on the control board. Unfortunately, replacing the board didn't fix the issue like the last time it occurred. Any ideas on the actual problem. I appreciate the humor.

 

If you get 24v to the condenser it's got to be right there.Could not bring up diagram.Pressure switch or something.I might try if you get the 24v to go direct to contactor for a short bit to test.That's bypassing everything so for a short time.

 

The wiring diagram you linked to shows an optional high/low pressure switch in series with the 24VAC going to one side of the contactor coil (low voltage side). I don't know if your unit has the pressure switch or not, but if it does, check to see if it's open. If so, then you either have a bad pressure switch, or the system is likely low on refrigerant resulting in the pressure being too low, tripping the switch (assuming it's a low pressure switch).

 

Guyold, Here is a pic of the wiring schematic.

Guyold and Bob14525,

I did not get 24vac at the lead identified in the pic below last time I checked. I was getting 24vac on the top lead on the contactor (above the red text in the pic). Would you happen to know where I could get the correct wiring schematic for my heat pump? If there is a low pressure switch, would it have a button similar to a thermal fuse on an oven that could reset the system.

 

sounds like a pressure switch is tripped. Are you 100% sure you rewired the new board correctly?

 

When you check for voltage on contactor...... don't check to ground. Check the two blue wires directly on the contactor. I highlighted them with orange arrows.

 

PJmax,

I checked voltage at the two leads where the orange arrows point to in your picture. 0 VAC when the button is manually pressed in.

I also checked voltage at every lead on the control board today. See pic for readings. All voltage readings were taken when t-stat inside was set to cool and contactor button was pushed in:

 

points to a refrigerant pressure problem.......................

 

Should I try replacing the low pressure switch first before calling out a professional? Is there a possibility of a refrigerant leak when replacing the low pressure switch? What levels on the control board would typically point in the direction of the low pressure switch or refrigerant issue? Sorry for all the questions, I am an inquisitive network engineer type not an HVAC tech.

Thanks!

 

NO, you can't legally do that. You must be EPA certified to do anything with a sealed refrigerant system. It could be a low or high pressure issue, Its hard to say without seeing a schematic or being there to know what your system has. You have 30VAC going out PS1 on the control board, but 0VAC coming back to PS2.

 

hvactechfw, It was indeed a low pressure leak as you pointed out. It leaked 13 lbs of R-22 out of the accumulator. The cost to fix the 7 year old unit was going to be $875 for the accumulator, drier, and Freon, in addition to the $170 for the service call/diagnosis (I'm in the wrong business). Now I'm in the market for a new A/C unit.

This is an exceptional online community for us DIYers, and I greatly appreciate everyone's input. Unfortunately, it wasn't a better outcome, but at least I'll have a warranty and a new unit.

Thanks again!