Turned ac off from thermostat but condenser fan still runs

Problems related to residential installations.

Turned ac off from thermostat but condenser fan still runs

Postby mongoose5271 » Tue Jul 26, 2011 11:02 am

I have a Janitrol A/C unit and it's been running fine (just recently bought the house, so haven't used it all that much) but yesterday when I shut the unit off from the thermostat, the condenser fan kept running. I waited for about 30 minutes and finally went out to the unit and pulled the fuse plug (is that the right term?) from the box near the unit. I then waited for about an hour and put the plug back in and the fan started going immediately. I took it out again for fear of the motor burning out. What do I do? I'm pretty handy but please, if you're going to respond with something like "check this or check that" then tell me where "this or that" is located on the unit because I don't know much about A/C.
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- Turned ac off from thermostat but condenser fan still ru

Postby heatseeker » Tue Jul 26, 2011 11:27 am

Most likely you have a stuck contactor which is located inside of the electrical housing of the condenser unit. Don't go stickin your fingers in it cause you could get electrified. A repair company should have a contactor on the truck so you should call one. The other possibility is your unit might have a shorted winding causing a back feed of electricity to the motor in which case you need to call the repair man or woman.
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- Turned ac off from thermostat but condenser fan still ru

Postby mongoose5271 » Tue Jul 26, 2011 11:43 am

heatseeker -
> Most likely you have a stuck contactor which is located inside of the electrical
> housing of the condenser unit. Don't go stickin your fingers in it cause you could
> get electrified. A repair company should have a contactor on the truck so you should
> call one. The other possibility is your unit might have a shorted winding causing
> a back feed of electricity to the motor in which case you need to call the repair
> man or woman.


What do you think a rough estimate of the cost should be?
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- Turned ac off from thermostat but condenser fan still ru

Postby heatseeker » Tue Jul 26, 2011 3:56 pm

There's no telling, could be cheap could be expensive. Try to fix yourself could be very expensive.
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- Turned ac off from thermostat but condenser fan still ru

Postby mbales » Thu Jul 28, 2011 1:59 am

You can confirm a stuck contactor pretty easy.
Unplug that block again by the unit while it is running but the thermo is calling for nothing.
Take the cover off the business area of the unit, should have labels on that area, and a mess of screws to take it off.
Look for this, with some serious looking electrical wire coming/going from it, and some finer thermo looking wire going to it.
*.*/Category/10-contactors.aspx

And you'll probably find it jammed closed. Just tap the unit with the end of the screwdriver gently and it should pop open.

You may find a bug got in there and fried, holding it closed.
You can clean that area out too to confirm easy movement. Should be able to push the upper (relative depending on installation) plate down easily.
After doing that, plug block back in. Should be off.
Go turn thermo to call for cool. Should be on.
Go turn thermo off, should turn off.

Unplug block again. Put cover back on.

If it got stuck again, you can decide now that you have looked at it, how comfortable you feel in replacing it, or if more cleaning would be in order.
Don't spray in water!
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- Turned ac off from thermostat but condenser fan still ru

Postby nomadpeo » Thu Jul 28, 2011 7:47 am

the contacts on the contactor are probably welded together due to a surge. when the signal is disconnected from the coil operating this contactor, the high voltage relayed through its contacts stays intact. with no call for cooling, the fan inside is also off. this is a condition that can take out your compressor. leave it off and call a qualified service company. the burnt contactor is a symptom of a bigger problem, possibly involving a run capacitor, a starting problem requiring an additional hard start kit, a compressor failing, a freon level issue, a fan motor going south or a high resistance due to a baked wire. have it diagnosed by a professional. it could possibly save you money in the long run.
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- Turned ac off from thermostat but condenser fan still ru

Postby heatseeker » Thu Jul 28, 2011 9:01 am

don't go sticking your fingers in the unit even after you disconnect the fuse box because some installer could have hooked up the wiring wrong and you still could get a big jolt. Anybody thats been a tech for a fair amount of time could tell you that. Thats why you should leave high voltage work to the pros. Is it worth your life?
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- Turned ac off from thermostat but condenser fan still ru

Postby nomadpeo » Thu Jul 28, 2011 11:11 pm

i agree with your last statement heatseeker.
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