I didn't try the contactor yet. I just don't want to do anything to screw it up to cause more damage

 

I work on commercial garage door openers all the time and have some knowledge of how relays,capacitors and contractors work but this thing has me confused

 

You need a voltmeter and check for power on board between y and c. I am not at home to type a long troubleshooting guide. You really need a voltmeter. I don't recommend pushing the contacts in as it is 240 volt. If you can get a voltmeter pm me your number and I can walk you through some steps.

 

Thanks a lot

 

Pushing the contactor in wont harm anything. It'll just start the fan and compressor in the condensing unit. Absolute worst thing you can do is hold it down for a long time, (hours and hours) and you turn your condensing unit in to a block of ice. I recommend giving it a try as it'll immediately tell you if that half of setup is working or not. And not all units are 240. Some are 115. Not that is makes much difference.

 

I am not going to get into an argument about pushing in the contactor, it is dangerous and can kill you if something goes bad! I have never seen a 120 volt set up on a condensing unit, not going to say they don't exist, but again, I have never seen one. Even at that, 120 is enough to kill you. Now we all know that it's not the volts but the amps that kill you, with that said, what is at that condensing unit CAN kill you and I recommend that you DO NOT do that! Sorry if that sounded dickish, do not mean it to be, I just take safety very seriously when working on units.

Now if you choose to push the contactor in, it can cause damage. If you are low on refrigerant it can damage the compressor, as the refrigerant is what cools the compressor. Probably won't, if it is done quickly enough but not worth it as it does not tell you anything that a voltmeter and some jumper wires on the low voltage side cannot tell you.

There are so many issues it could be, so these troubleshooting tips may seem to jump all over the place, but I will try to make them as much in order as I can.

I would start in the furnace (air handler), I would check to see if you have 24 volts at terminals Y and C on the board. If you do have power there, then I would go outside to see if you have have power at the coil on the contactor. If you have power there then you need to see if you have power across the contacts. If you do not have power across the contacts, then the contactor is bad. If you do not have power at the coil on the contactor, then you need to check power in and out of the pressure switches in the condensing unit. If you do not have power in to any of them, then you may have a broken wire from the board to the contactor coil. If you do have power in and nothing out on one of them, you need to find out if it is low or high pressure switch. Almost certainly going to be low pressure though. At this point you will need to hook up gauges to verify you have low pressure, if you have pressure that is not low, then the pressure switch is bad.

Now back to Y and C, if you do not have power at Y and C, then you need to check the thermostat or the wires from the thermostat to the the board. You pull the thermostat off to expose the sub base, you can jump between R and Y. If this energizes the condensing unit, then your thermostat is bad. If it does not energize I would start looking at wiring between the thermostat and board.

Earlier I wanted you turn the fan switch on the thermostat to the on position and see if the blower in the furnace energizes. This eliminates a few things, like the transformer and blown fuse on the board, etc.....

You stated the furnace works, so I am assuming the board has power and the last step is not needed, but worth a check. You can also check terminals R and C at the board to eliminate the step of turning fan switch from auto to on. If you do not have power at R and C, then I would look at the transformer or the 3 or 5 amp fuse on the board, then check primary side of transformer for power, if you don't have primary power, you need to go back to the SSU or SSY (switch on the side of the furnace that looks like a light switch) and look at the slow blow fuse there. If you do have power at primary, then check secondary side. If no secondary side power then the transformer is bad.

Does the air handler blower come on when you turn the thermostat to AC and call for cooling? If nothing comes on, I would think your thermostat is bad, and again this can be checked by jumping the R and Y terminals on the sub base of the thermostat. Your board could be bad too, but that would require to find out what pin outs are on the plugs and check in and out to see if a relay on the board is bad.

I may have and probably missed something why trying to type this. It is much easier to do when you are sitting in front of it instead of trying to recall from memory. I am no expert in this field, but I have had some education and been in the field for awhile. Everyone has different troubleshooting techniques and styles of figuring what is wrong. Like, hey, push the contactor in and see if the fan and compressor work. Again that tells you nothing that cannot be found out safely with a voltmeter and jumper wires. And even after pushing in the contactor, you still need to do the troubleshooting steps mentioned above.

If you are checking the voltages at the air handler, when that bottom cover is off you do need to have something to hold the door switch closed or else you will not have any power anywhere.

 

I have my own HVAC business. Most everything I read so far is correct. An easy (safe) way to tell if you have 24 volts going to the contact on the AC is have someone turn the ac on at the thermostat, while you watch and listen outside. You'll hear & see the contactor click on. If it does you can rule out any furnace issue. Any other questions you have feel free to ask.

 

Well did the technician come out and fix it? What was wrong?

 

My dumb *** wired up the thermostat that I replaced a while ago wrong.

 

Hahaha, I have ran into that on many occasions, usually the customer fails to mention they replaced the thermostat! Then once the diagnosis has been made, they are like........ Oh yeah, I forgot, I put a new thermostat on! Always tell the technician everything, it will save them time and you money, the homeowner is one of the best troubleshooting tools the technician has.

How much did they charge? Could have saved you the money if you had a voltmeter and followed this step from above:

"Now back to Y and C, if you do not have power at Y and C, then you need to check the thermostat or the wires from the thermostat to the the board. You pull the thermostat off to expose the sub base, you can jump between R and Y. If this energizes the condensing unit, then your thermostat is bad. If it does not energize I would start looking at wiring between the thermostat and board."