air handler will not turn off

Problems related to residential installations.

air handler will not turn off

Postby mm2580 » Wed Aug 03, 2011 2:51 pm

I have an older Kenmore a/c / propane furnace and air handler. This house was a foreclosure and I have had it for a few months, so I do not have much history on the unit or installation info. Immediately on getting possession of the property (it was cold out), I discovered that the air handler blower would turn on apparently randomly regardless of what the thermostat was set at. Now that it is hot out, we are having difficulties with a/c. I am hoping somebody can point me in the right direction. It seems to be an electrical issue to me.

So...this is what -

The air handler and compressor will run and keep the temperature as set on the thermostat. It will continue to work fine for several hours.

At some point, the compressor unit will not come on but the air handler will, then the air handler will not shut off despite turning the thermostat to the off position. The only way to stop the air handler (that I know of) is to turn it off at the breaker.

Once the breaker is off, turning the breaker back on will immediately kick on the air handler but not the compressor, regardless of the thermostat setting.

Once the breaker is off for several hours (the breaking point seems to be around 4 hours), turning the breaker back on will not turn on the air handler automatically and the unit will function properly as controlled by the thermostat...for several hours, until it again reaches the point where the compressor and air handler do not come on concurrently.

If both are running properly and I shut off the thermostat, everything will shut down properly. However, even with the thermostat in the off position, the air handler will kick on indefinitely at some point on its own accord, and again cannot be turned off unless hitting the breaker. If this occurs, the compressor unit will not come on, ever, unless the breaker is off for several hours.

This has been occurring since we have had the house. Last night I noticed that the a/c was still functioning properly before I went to sleep (unusual). I shut down the thermostat and everything turned off. I left the breaker on. This morning I awoke to the air handler running but no compressor. I turned off the breaker. Approximately 3 hours later, when we went to turn on the a/c, the compressor would not come on, air handler was stuck on. The thermostat was showing a "flashing snowflake," which apparently indicates a fail-safe overheating measure to keep the compressor from kicking on and off too quickly and overheating, but the compressor had not been on at all.

After having the breaker off a couple more hours, it is back to normal. Compressor and air handler cycling as usual. Tonight will be the same story again.

I have tried reprogramming and resetting the temp on the thermostat. Resetting the target temperature works fine, if the system is in "running properly mode," that is, the air handler is not running indefinitely. Once the handler goes rogue, all bets are off. No amount of programming on the thermostat will affect the air handler.

Any thoughts?

To me this seems rather odd as sometimes the air handler follows the thermostat, other times not so much. The compressor always turns off by the thermostat, but not on. I cannot rule out the possibility that the unit was wired by a previous owner and was done totally incorrectly, as was the case with the plumbing and electrical systems, but I do not know enough about hvac wiring to determine what type of fault this could be.
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- air handler will not turn off

Postby ss1968 » Thu Aug 04, 2011 7:38 pm

I have the same issue although a different unit(rudd deluxe 90 plus). The blower in the furnace, at times, will not kick off when the thermostat temp is reached although the outside A/C unit does. When this happens the A/C will not kick back on when the temperature warrants. The only way to shut off the blower is to cut power. After a while, turning it back on, it will operate normally for anywhere from 12 hrs to 2 weeks and then start again. The A/C does not appear to operate unless they switch on concurrently. I have searched every discussion board I can find and havent found the same problem, only a similar problem related to the heating function. Since the heating is handled all within the same unit, not two seperate units as in the A/C operation, I dont think those apply. This am i messed with the wires on the limit switch and it shut off. May have been just a coincidence since I thought the limit switch was related to the heat function. I would like to see a good reply to this problem besides "make sure your thermostat is on".
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- air handler will not turn off

Postby heatseeker » Fri Aug 05, 2011 9:45 am

Make sure your tstat is on. Really though, sounds like some relay problems or circuit board problems maybe a faulty safety switch on the heating side, yes that will happen or maybe just some loose control voltage wiring. Also condenser contactor could be sticking. This is basic troubleshooting stuff that a competent tech could figure out, if its not a simple tstat issue or loose wire why waste time and energy letting the equipment operate this could cause things like compressors or blower motors to fail then you will really have to reach into your pocket. Your next post will read "my compressors not running could it be the fuse or breaker?' No you tried to save money and it cost you more, come on people think about it. athanks I'm done.
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- air handler will not turn off

Postby ss1968 » Fri Aug 05, 2011 9:12 pm

Actually it is lose wiring in the limit switch. I was able to fix it. The problem is finding a "compitent tech". Peasonally I can't afford the hunderds of dollars...multiple service calls...trial and error method of a tech. My local hvac company came out in the winter for a heating problem with the same unit. It wouldnt ignite or heat. I noticed that the the water line was clogging when trying to drain. When it did drain, it would work a while later. So they came out, had no clue so i told him what i observed. He cleaned out the drainage and it was totally clogged. So the unit still doesnt work. so he says its a shot heat exchanger and i need to replace the whole unit. He proceeds to show me rust lines on the exchanger with a flashlight and says the unit is shot, exchanger it cracked, and there is too much air being taken into the exchanger and it will continue to blow out the pilot. Meantime the unit will still not ignite. So 30 minutes later slick willie shows to quote me a new unit. 3k. Well i am thinking about what to do and after about 4 hours the unit sparks, fires, and works all winter. The problem? the water from the clogged line was backing up into the unit, getting the inside wet, and keeping it from * lines were from the backing up water. So I prefer to find someone with a similar problem that found a solution.
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