Hopefully someone can help. During the summer my condensate line clogged from my AC unit. My neighbor helped unclogg it, but while unclogging it we also took the cover off of the “coils”? where the water runs and drains. When we put the unit back together, the fan would not shut off. I decided to wait a few days before worrying about it. Several days has now turned into 6+ months and the fan still has not shut off. The heat & AC both work as far as turning on based on the thermostat, but the fan never shuts off.
Today I dismantled the unit as I did in the summer and put it back together. I guess I was hoping to undo the vodoo put on it the first time. No such luck.
I will call a heating/air repairman if necessary, but I was hoping it might be a common problem that could be easily and cheaply repaired. Perhaps a breaker or something?
Any guesses?
Replies
I don't know of any fan control circuitry that would be in the A-frame area of your furnace. I think this is more coincidence than Vodoo. Although I hope you took the power down before doing any work on the AC.
The fan is run off a relay that is controlled by the termostat. Might be the relay is stuck and if it is, it should be replaced. Also check to see if a Fan delay is working properly ( if one is installed) If This all sounds Greek then a call to a HVAC service tech is your best bet.
Also a quick check is make sure the "fan on" switch is not selected on the thermostat. This should be set to "auto fan"
Good luck.
Call a HVAC guy. Furnaces usually don't run on voodoo...
> Call a HVAC guy. Furnaces usually don't run on voodoo...But they often stop due to doodoo.
Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot
My trailer furnace fan stopped due to wasp doodoo.
Mud wasps. Paper wasps built all over inside it, the mud wasps picked a single spot inside the squirrel cage.
Doesn't take much to keep one from starting.
Joe H
If the HVAC guy can't figure it out, call a witchdoctor.
First, check the thermostat to see if the "fan" switch is set to "on" instead of "auto". (Kind of an "Is it plugged in?" thing, I know.)
Next understant that in a "conventional" forced air furnace with A/C there are two different things that turn the fan on:
1) The fan relay, in many units a plug-in relay stuck in a socket on a junction box inside the unit.
2) The fan/limit switch, a sort of thermostat that sits against the area above the burner (but below the A/C coils), with a thermostat probe that sticks into the airflow of the furnace heat exchanger. (However, if you have a downward blowing furnace, the "fan" function of this switch is replaced by a separate thermal timer. If you have that you need to come back for more info.)
Either of these could be the problem.
If you can find the fan relay, and if it looks like the sort that unplugs, FIRST TURN OFF THE POWER AT THE BREAKER (or unplug the furnace, if it's set up with a plug) and then see if you can pull out the relay. There may be a retaining wire across it holding it in. If you get the relay out (is has nothing to do with heating, so you can leave it out for awhile), restore power to the furnace and see if the fan is still running.
If pulling the relay fixes the problem, then you have:
1) Broken thermostat (cheap and easy to replace)
2) Shorted thermostat wires (a pain in the posterior, unless you can easily see a short just looking at the wires)
3) Stuck relay (cheap and easy to replace)
(And obviously if you can't find and pull out the relay, these three things could still be at fault.)
The fan/limit switche is a deal that looks maybe a little like an index card box, and, if you pull off the cover, looks kind of like a timer switch inside. There is a dial, with three little levers arranged around it's perimeter. (IMPORTANT: NEVER ATTEMPT TO ADJUST THE LEVERS WITHOUT HOLDING THE DIAL TO KEEP IT FROM TURNING. Failure to observe this precaution can damage the thermostat sensor.)
But fan/limit switches don't generally get out of adjustment unless someone monkeys with them. Did you guys perhaps monkey in there when working on the system earlier?
Fan/limit switches can fail, of course, and it may be that yours has and needs to be replaced.
When I frist moved into my house I had that same problem. It was a limit switch (I cant remember if it was high or low limit). It was a relatively cheap fix. My switch was a bi metal type and it just gave up and stuck in the on position.