Central Air not turning on


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Old 12-15-09, 10:58 PM
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Central Air not turning on

I have a Rheem RBHC-21J11SFC that just decided to stop turning on. I've checked all the circuit breakers, they have all been reset and are not tripped.

After taking the cover off of our old Thermostat, I replaced the batteries, no go. the thermostat circuit board looked damaged around the screws, so I replaced it, connected all the wires in the same way as the old one (RC, RH bridged, W, Y, G).

I've tried both cool and heat, no luck. I see no ice on the outdoor part of the unit. Unit has a new filter.

If I flip the breaker built in to the front of the central air unit, I notice it sounds like the electricity is cutting off, so it seems the unit if getting power. Also, when I turn the thermostat to a position where the AC SHOULD kick on, a familiar "click" comes from the thermostat, but the AC unit just does not follow suit.

Odd thing: this morning, the unit suddenly turned on, we hadn't touched the therm since last night. Once it shut off, it did not come back on (again).

HELP
 
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Old 12-16-09, 04:54 AM
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Sound like you may have a loose low voltage connection. Do you have a meter and know how to use it?

From the M# you posted it seems you have a heat pump, however the thermostat terminals you posted indicate the stat you put on will not work for your system.

Did you have any wires left over?
 
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Old 12-16-09, 06:16 AM
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Originally Posted by dun11
Sound like you may have a loose low voltage connection. Do you have a meter and know how to use it?

From the M# you posted it seems you have a heat pump, however the thermostat terminals you posted indicate the stat you put on will not work for your system.

Did you have any wires left over?
I just mimicked the wiring on the original thermostat I replaced. There are 4 wires that are/were in use:

Red wire was leading to RC (which was bridged to RH)
Yellow to Y
Green to G
White to W.

Old therm only had connections for the 5 spots mentioned above. (rh, rc, w, y, g), I made sure to label them and move them over to the same spots on the new therm. I guess it's possible the original builders did some kind of ghetto-rig to make the old therm work with this AC unit, not sure.

New therm is universal and has spots for all types of combinations of wires. I placed the wires in the matching spots (along with the bridge) and set the jumpers as stated in the manual. Since it's universal, I should be able to get my unit to work with it, assuming I can sort out where the wires need to be placed.

The new therm is a ritetemp 6036, original one is a RobertShaw 9600.

No wires left over that were already in use. There is a blue wire in the cable bundle coming out of the wall that was cut very short and was not at all in use on the original therm.

I still have the original therm, so I can reconnect it if need be. Like I said, this stopped working while using the old therm, I just used this situation as an excuse to swap it out for a sexy new thermostat (hoping it would fix the problem)

I have a multimeter and I know how to (basically) use it. What voltage should I be looking for on the wires?

thanks for your help!
Carlos
 
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Old 12-16-09, 06:57 AM
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If you put the fan switch on the stat from "auto" to "on" does the blower work?

Turn off power to out door unit first.

At the outdoor unit check the disconnect on the wall, take off the cover after opening the door and chk if there are fuses in there if so are they good?

If they are good turn power back on to unit and set stat to call for cooling

Check the contactor in the condensing unit you should have 220V at L1 and L2 "incoming power" also check the contactor coil should have 24V.
 
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Old 12-16-09, 07:07 AM
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If you put the fan switch on the stat from "auto" to "on" does the blower work?

Turn off power to out door unit first.

At the outdoor unit check the disconnect on the wall, take off the cover after opening the door and chk if there are fuses in there if so are they good?

If they are good turn power back on to unit and set stat to call for cooling

Check the contactor in the condensing unit you should have 220V at L1 and L2 "incoming power" also check the contactor coil should have 24V.
 
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Old 12-16-09, 07:44 AM
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Originally Posted by dun11
If you put the fan switch on the stat from "auto" to "on" does the blower work?

Turn off power to out door unit first.

At the outdoor unit check the disconnect on the wall, take off the cover after opening the door and chk if there are fuses in there if so are they good?

If they are good turn power back on to unit and set stat to call for cooling

Check the contactor in the condensing unit you should have 220V at L1 and L2 "incoming power" also check the contactor coil should have 24V.
Nope, switched to "on" and the blower is still not .... blowing

The outdoor unit: The disconnect on the wall has some kind of "piece" that can be removed to open the circuit (don't know how to properly describe this). It's kind of a plastic handle that is pulled and removed to open the circuit... when inserted, the circuit is complete. I see no fuses or breakers there. (I can post pics of anything if that may help... let me know)

You said:
Check the contactor in the condensing unit you should have 220V at L1 and L2 "incoming power" also check the contactor coil should have 24V.

Where do I do this? I'm assuming I have to take panels off the condenser to reach the inside of the unit for this? Should I post the condenser model#?

Thanks again,
Newbie
 
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Old 12-16-09, 08:28 AM
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After you open the door on the disconnect below the pull handle you have to remove that cover to see the wire and or fuses.

And yes you have to remove the panal on the condensor where the elec wires enter the unit to get to the contactor etc.
 
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Old 12-16-09, 08:37 AM
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Originally Posted by dun11
After you open the door on the disconnect below the pull handle you have to remove that cover to see the wire and or fuses.

And yes you have to remove the panal on the condensor where the elec wires enter the unit to get to the contactor etc.
Thanks for all the great info... when I get home I'll check the wire/fuses and get into the condenser!
 
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Old 12-17-09, 11:25 AM
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Ok, the contactor Coil has 24v, but incoming Line 1 and Line 2 only have ~122v each.

EDIT: there were no fuses

Air started working normally for several hours last night, blower would turn on when set to "on" , the whole nine yards, then it stopped working just as suddenly as it started.
 
 

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