HVAC won't turn on at all...for no obvious reason.


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Old 06-20-10, 11:01 PM
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HVAC won't turn on at all...for no obvious reason.

HVAC is heat + AC, had separate fan AUTO/ON control. Stopped turning on.
Flipped the breaker back and forth. Checked thermostat batteries-corroded. New batteries-thermostat still dead.
Changed thermostat.
Installed a new Honeywell RTH230B.
The wires are correctly matched, I took a picture of the old one (Lux TX500E which I hated) to be able to double check. 4 wires, read yellow green read white I think , plus jumper from Rh to Rc.
Still nothing. Seems too coincidental the HVAC would break right when the batteries died.
Any ideas? I'll call a service person if necessary, but would hate to do that just to find out there is some switch or breaker on the unit I could have fixed myself.
 
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Old 06-21-10, 04:30 AM
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Does the furnace fan come on when you switch the fan switch to "ON"?

When you changed out the t-sat, did you turn off the power on the system?

If not, you may of shorted/touched the wires, and cause either the fuse on the furnace to blow, or the transformer burned out.
 
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Old 06-22-10, 01:14 AM
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Originally Posted by Jay11J
Does the furnace fan come on when you switch the fan switch to "ON"?
No

Originally Posted by Jay11J
When you changed out the t-sat, did you turn off the power on the system?

If not, you may of shorted/touched the wires, and cause either the fuse on the furnace to blow, or the transformer burned out.
Mmm...I set the Tstat to OFF. But I'm wondering if I thought to shut off the main breaker again. Maybe not, dummy me
(Although I'm quite sure I didn't short the wires, I moved them one at a time).

Seems time to call a technician, thanks.
 
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Old 06-22-10, 04:34 AM
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Yeah, if you didn't turn off the main power on the equipment, a simple little short can blow a fuse or burn out the transformer.

Not sure what brand you got, but check on your board for a fuse, most brand has fuse like you find in your car. It may be hard to find since there may be a lot of wires. If it's an older one, then it may not have it.

Do you have a meter to check for power?
 
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Old 06-28-10, 11:02 PM
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Did you get it going?

Does outside unit come on? If you take red wire and jump to green the fan should pull the fan relay in. If outside unit comes on that's a start. Go to where air handler (furnace) is and look for transformer, see if you are getting 24 volts from where red and common connections are. When I put in thermostat's I always try to stay away from the ones that run on just batteries.
I like the ones that also run off the common 24 volts wire set up.
If you have 24 volts than see if you hear fan relay click. You may have a bad fan relay. The first thing is to see if you have control voltage 24 volts to thermostat, condensing unit, indoor fan relay, etc. Let us know...Beer 4U2
 
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Old 06-29-10, 01:54 PM
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I'm not AC expert at all but I had something similar happen. The blower unit door had vibrated open. So the safety switch was not depressed and the unit would not start.

Just something to check before calling someone.

Daniel
 
 

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