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This the second time this problem has come up. Our home has electric heat. For the second time I awoke in a home close to 80 degrees. Even though the thermostat was no longer calling for heat, the central air fan and the electric heat strips were still running. Only way I could stop it was to cut the breakers to the unit. The first time this happened, I thought the digital thermostat may be going out. While the breaker was off, I went to Walmart (after midnight) and found another thermostat. Before installing the new thermostat, I turned the breaker back on and everything is working fine. Few weeks later it happened again. This time I managed to get the AC compressor to turn on to cool down the home. Problem was the electric heat strips were also running so the air wasn't as cool as it should have been. Once again, left the breakers off for a few hours and when turned back on, everything seems fine.
Is this a problem with the Relay (hope so cause it's even cheaper than the thermostat)?
Yep, quite likely a relay that has corrosion and has become "sticky". If the relay is easily accessible, you can tell if this is the problem by waiting to the next event, then tapping the relay with the handle of a screwdriver. If it is sticking, this will release it. If the coil to the relay is energized and it doesn't release, the the problem is most likely in the controller board.
Yep, quite likely a relay that has corrosion and has become "sticky". If the relay is easily accessible, you can tell if this is the problem by waiting to the next event, then tapping the relay with the handle of a screwdriver. If it is sticking, this will release it. If the coil to the relay is energized and it doesn't release, the the problem is most likely in the controller board.
Getting to the relay isn't the problem. Tapping on the relay is the problem. It's surrounded by a series of wires which makes giving it a good tap difficult. My unit is a mobile home Intertherm unit. The I literally have to lay on the floor to look directly at the relay. By "controller board", do you mean my digital thermostat? Keep in mind this unit is at least ten years old but the thermostat is all digital and only a few years old. I don't doubt it's possible these digital thermostats can go bad after a few years.
Oh, forgot to add that the first time this happened, I even went so far as to power down the digital thermostat and remove it from the wall but it still kept running. According to the Grainger catalog, these types of relays cost less than $20. Just need to find the correct part number for the relay and get with Grainger Monday when they open.
Usually the unit itself has a computer board that provides the power and switching needed to actuate the relays (contactors). If you see some capacitors and transformers and heat sinks on a circuit board, chances are that is the controller board. Do be careful. Some caps can retain a nasty charge even when the breaker or disconnect are eliminating outside power. There should be a schematic in your destruction manual or a basic schematic on the back of one of the tin covers.
Usually the unit itself has a computer board that provides the power and switching needed to actuate the relays (contactors). If you see some capacitors and transformers and heat sinks on a circuit board, chances are that is the controller board. Do be careful. Some caps can retain a nasty charge even when the breaker or disconnect are eliminating outside power. There should be a schematic in your destruction manual or a basic schematic on the back of one of the tin covers.
the schematic didn't show a circuit board. It showed a trasformer, relay, and wiring to the heating element and the fan. What I may do later is take a photo and post it online later.
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Be careful laying on the floor doing this Dave!!
