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A/C contactor, not engaging itself... need wiring diagram


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08-15-08, 06:29 PM   #1 (permalink)  
A/C contactor, not engaging itself... need wiring diagram

I thought it was just the contactor that was bad in our outside unit, as the unit worked fine if you pressed the switch manually... so I got the replacement for the contactor we had and installed it, but the same thing- if you press the switch both the fan and compressor come one, otherwise, with just turning the thermostat, nothing occurs. I'm wondering if i'm hooking it up right (since the wires have been undone in the past) Can anyone tell me what goes to the L1 L2 and T1 T2... it is a 2 pole 24V contactor. It engages when you push the switch, but will not stay engaged (you have to keep the button pushed for it to work)... any suggestions or wiring diagrams would be greatly appreciated.

 
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08-15-08, 07:10 PM   #2 (permalink)  
are you receiving 24 volts at the low voltage side of the contactor?...if not time to trace the wiring back to it's origin at the furnace air handler and check there. Sounds like high voltage may be right but could be one of many problems on the low voltage end.

 
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08-15-08, 07:36 PM   #3 (permalink)  
I won't be able to check this evening, so I'll have to wait until tomorrow... what are the possible outcomes if it's not showing 24v?

 
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08-15-08, 07:36 PM   #4 (permalink)  
Posted By: c2whitmore Can anyone tell me what goes to the L1 L2 and T1 T2... it is a 2 pole 24V contactor.
Sounds pretty basic. How did YOU hook it up?

......................

In response to post #3: If "nothing happens"(including no inside blower running) when turning stat, make sure furnace/handler circuit breaker is on. That a switch and/or combo switch and fuse on the side of the air handler/furnace is on/good. That possibly a 3 amp fuse, on a circuit board, in the furnace/air handler is not burned. That the blower door on the furnace/handler is not ajar. That you have 120 volts to it inside the handler/furnace. That you have 24 volts across the transformer's outgoing low volt wires. That you have 24 volts coming into and out of the thermostat. (Try to see if you can get indoor blower to run in say a heating mode either with stat set to auto or on, if you have central air with forced air furnace/handler)


Last edited by ecman51; 08-15-08 at 07:56 PM.
 
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08-15-08, 07:42 PM   #5 (permalink)  
I didn't write down how it is connected from the capacitor, circuit board, etc... and it's dark now, so I'll have to go out tomorrow in the morning. Though I know the major black and white connectors are going to the L1 and L2- the T2 and T1 end has two connections on each and the left and right have one connection to the coil of the contactor (I want to say that one yellow connection is coming from the circuit board)... Like I said though, I'll check them all in the morning... I just replaced it as it was and it had been messed with prior, so I'm unsure as to if it was hooked correctly to begin with.

 
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08-15-08, 07:55 PM   #6 (permalink)  
the low voltage signal could be anything from a low pressure switch, to damaged wiring from the a/c to the house from a weed whacker, to a faulty stat, to a bad board or fan relay. Being handy with a volt meter will answer all these questions.

 
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08-15-08, 08:02 PM   #7 (permalink)  
Please let us know if the indoor blower also does not work no matter what setting you put the stat on.

 
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08-15-08, 08:07 PM   #8 (permalink)  
The inside unit works- when placed on cool, you can hear it click at the thermostat to engage the outside unit- though nothing on the outside unit.. the fan mode works normally and as long as the contactor is manually pushed, everything works normally. I'm guessing the contactor isn't getting the signal to engage.

 
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08-16-08, 05:22 AM   #9 (permalink)  
I think your guessing correctly.

As stated earlier, you need to trace the 24v signal to the contactor.

Start at the stat and work towads the outdoor unit.

Just hearing the relays click in the stat doeas not mean that the contacts are actually closing.

Very hard for any of us to even start looking for correct diagrams, manuals etc. without a Manufacturer, Model and Serial Number.

 
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