HVAC Trouble

wrangler1217 · Jul 9, 2015

This isn't exactly pool related, but with as many people out there with all kinds of diverse backgrounds - I figured I'd try here first. Please move/delete if needed.

But my A/C compressor went out yesterday afternoon, so my pool is now the most comfortable place on my property, lol. Got home from work and the temp inside was 85 F...sweltering. My thermostat is a digital/programmable kind. When it is set on "Auto"....the blower/fan/handler whatever it is does nothing. When I set it to "on", the blower cuts on...but does not cool at all. So, with the blower on...I went outside to check the compressor. It was off. I checked and reset all the breakers...all good - the line has 240 going into the unit. The contactor is suspect though. If I manually push it in, the compressor cuts on just fine. So I googled it, and I'm supposed to have a 24v reading on the two side terminals of the coil from the wires coming from the thermostat. I got nothing. I even disconnected the thermostat wire from the coil and tested them then, and I still got nothing. So I followed the thermostat line back to the blower where the current is sent from - and I'm reading 24v there.

Originally, I thought it was the coil on the contactor...but after thinking about it - It's gotta be something else if I'm reading 0 from the outside thermostat wires, right? Does anyone know if there's some kinda cut off switch...like a pressure switch, that'd cut off the voltage from the thermostat wire in case the pressure got too high? And would how close to the unit would it be?

In my other house, the A-coil froze over and I had to let it thaw out - then cleaned the fins really good on it. Could this also be a cause too?

Thanks in advance!

Pool Tool · Jul 9, 2015

I don't know much about the contactor or switch, but a frozen coil is oddly enough a sign of refrigerant (freon) loss. I had a system that a small leak and it would freeze the coil.

cowboycasey · Jul 9, 2015

so, I have done this also, I usually trouble shoot it down to what I think it is and then call the pro's... I have managed to get better rates for doing this than if they came out and did the trouble shooting...

I just had to replace my indoor blower motor, i found out it was the motor, they found the motor, I went and picked it up the motor and they installed it.. saved me about 500 dollars that way...

if you know exactly what it is then you may be able to fix it, if not call the pro's

ps0303 · Jul 9, 2015

Well if your system has a overflow switch and the drain line is plugged up with gunk, it will prevent the unit from running. Not sure if it would kill the thermostat power or not. Some units have a fuse on the board inside also.

Good luck.

wrangler1217 · Jul 10, 2015

Well, I dug into it a little deeper and attempted to bypass the switch (if there was one) by running a separate line out to the contactor posts from the inside unit. I'm actually getting 21v from those leads...BUT I only get that when they're disconnected from the coil...with the contactor pushed in or out - doesn't matter, it's like that coil kills the current (if I'm even saying that right). But as safely as I could...I made a makeshift kit out of a rubber clamp and pvc pipe that pushed the contactor in at all times. So I let the unit run, and the house cooled down very easily from 85 to 72 in a couple of hours - so I've kinda ruled out the pressure theory, and the drain pan and pipes are good. The new contactor comes in today, so hopefully that'll fix it. Fingers crossed!

Knjakeman · Jul 10, 2015

This could be a couple of different things. If you have a pan switch or wet switch installed the air handler ( inside unit) , usually this will break the hot or common 24v feeding the t-stat. But it can be used to break any wire thus the yellow wire assuming color coded correct. If you don't have a pan or wet switch then the culprit sounds like the t-stat. If your thermostats calling for cool then you should have 24v at the coil outside.

Knj

Knjakeman · Jul 10, 2015

The best way to check if the contactor coil is good is by ohmmeter. With control wires disconnected you should read about 19 or 20 ohms. If it measures O.L then it's no good. If it measures 0 then it's also no good as that would indicate a dead short.

Knj

wrangler1217 · Jul 29, 2015

Meant to post this, but just now have access again to a computer (been on my 2 weeks annual training with the national guard). But while I was gone, a pro came to look at the problem. They said he fooled with it for a while, checking all kinds of different things. Even put new wiring in for the t-stat and out to the compressor...but still wouldn't work. Then he put on a new t-stat and the problem was fixed. $350 later. Well, actually $375 because I tossed his t-stat aside when I got home and replaced it with a cheap programmable one. It makes me feel a little better knowing that even he had trouble with it...at least until I look at the bill again

. Ah well, such as life.