I have an older air handler in my attic (20years) and an outdoor condenser unit that is about 10 years old. I just had one of those cheapo $30 maintenance services done, so I know that my freon level is OK. The guy mention that my rusted capacitor may go bad eventually. He noted that my plenum was detached and air ducts were damaged. Even with the attic being air-conditioned, due to the duct/plenum issues, I was still able to get the air down to 78 without having any real problems. I have since repaired the ducts and attached the plenum. The system was running very efficiently after the repairs. 3 days later, on the day my tenants moved in, the air started to suddenly blow hot, even tho the tenants had not adjusted the thermostat. When I got to the house to check it out, it was 99 inside and only 90 outside. It was literally blowing heat out of the vents. I figured this may be an issue with the thermostat, so I changed the batteries and got the unit to blow cold air again. The house then cooled from 99 back down to 80 throughout the day. Then the next day/this morning it started blowing hot again. So I thought I may need to actually replace the thermostat vs just change the batteries. When I put the new thermostat in, it was still blowing hot. So I got frustrated and put the old thermostat back up. It still blowed hot air, even on the settings that worked yesterday. Then in my extreme frustration, I disconnected the wires that go to the heating elements. Leaving only the a/c wires connected. Now it's blowing cold again. This makes no sense and is making me crazy (and my tenants upset). I'm worried it will start blowing hot air again tomorrow and i will have to call and pay for service. Does anyone have any ideas as to why this could be happening? Is there any troubleshooting I can do? The lines definitely weren't frozen. How can it go from hot to cold, hot to cold like that?...HELP PLEASE!!

 

Is this a heat pump system? If so, the reversing valve may be at fault.

$30 maintenance service? What did he do besides just look at it and take your money?

 

Thank you for your reply. Pretty much just look at it an take my money, haha, but I got to have my freon tested and pick the guy's brain. I knew what I was paying for ...Yes there is a heat pump. I did detach the orange wire that controls the reversing valve. How can I troubleshoot that valve? Is that something I can replace myself? I can do light electrical/plumbing on my own.

 

It will take a professional to replace the valve. But you need to check some other things before you replace the valve. Can you post the make and model number?

 

Unfortunately I cant make out the numbers on the unit since its gotten so weathered. It's a goodman inside and outside. The house is 800sq ft, so it's a smaller unit...Dumb question; how do I know if I have a heat pump for sure? The thermostat was originally wired for heat and I've never lived here in FL with a house that didn't have heat on the central a/c. I hadn't tested the heat since its summer. I do think I have it but I want to be sure. I have the white & orange wires disconnected from the thermostat as of now and it seemed to be blowing cool when I left. Thank you for your reply!

 

If the Orange wire was being used its probably a Heat pump. The only way to know for sure is open the unit up and see if it has a reversing valve. It could be the defrost board switching to defrost mode.

 

In your opinion; if it's blowing hot tomorrow, should I go ahead and call for service? Are there some things I could troubleshoot before I call for service? How much should a general service call cost? The company that did the $30 "service" has a $75 service fee. Thank you again for your help!

 

$75 is a fair price. There are a few things you check if you want to to get in to it.

 

I would like to get into the troubleshooting if you don't mind. I am not at the unit, since it's a rental. I will not be there until they text tomorrow complaining of heat. If you could provide me with a checklist of things I can possibly troubleshoot before I call for service, that would be great. I like to know what I may be dealing with, before some unscrupulous a/c guy comes over to scam a pretty young lady, haha. Thanks

 

Hey Nat, no problem. I will get back to you.

 

Ok first start the AC and let it run for 5 minutes. Then go outside to the unit, lightly touch the larger pipe. If this pipe is hot then it is in heat mode. Most likely the defrost board is bad.

 

The tenants say the air is working really well right now. We are in FL and they got it down to 75 at night/78 during the day with no problem. I have the heat wires (orange and white) disconnected from the thermostat right now. When the heat wires were connected, the air was cold- then hot - then cold - then hot, over the course of 2 days. When the air was blowing heat out of the vents (seemed like heat, not just attic air) the larger pipe on the outdoor unit was very cold, but never frozen. I can't do the troubleshooting step you suggest right now, but I have felt that pipe many times during this fiasco, and it was never hot, always very cold. Even while hot air was pouring from the vents. The tenants insist they don't care if I reconnect the heat. But I do want the unit to be running properly and I don't want to damage the system. I would like to get an idea of what the problem is. I really appreciate your replies and help! Thanks again skaggsje & tomf63

 

I would be inclined to leave well enough alone, at least for the time being. When the seasons change and it gets close to where you'll need heat, then connect up the disconnected wires and troubleshoot further. At least you then won't have heat coming out of the vents during the hottest part of the year.

 

Thanks, Bob. I think that's what I'm going to do. It will also be a lot easier to get a reliable tech out when the seasons change. This is a busy time for a/c repairs in FL, as you can probably imagine. I will likely be here asking more questions when winter comes and I play with those heat wires.