Wiring help with thermostat and condensor

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Scott Baz

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I removed old thermostat and only had a 2/22 wire red/white
(I have ran a new 5/22 wire)
Looked at furnace wiring and have 2 black wires from Fan limit switch (one on 24vac transformer other on gas valve terminal)
White wire to thermostat on other gas valve lug, then red wire from thermostat to other terminal of 24vac transformer
I don't see any fan contact wires.
So my question is how do I wire in the new AC condenser and also be able to turn the fan on and off if wanted?

Thank You In Advance
SBAZ
 

Stuff

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With a fan/limit switch the fan has its 120v feed switched. Lots of those old furnaces required an a/c kit to enable fan control. This basically added a relay for the fan in parallel to the fan/limit switch.
 

Stuff

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Picture didn't come through. Do you have a make/model number of the furnace?
 

DonL

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Not really. Do you have a schematic ? That will show what needs to be done. Will also avoid smoking something.

upload_2019-7-25_9-34-38.png





 
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Stuff

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Something missing here. If there is a condenser then a pro should have been there to install and should be able to wire this. DonL's pic shows old system. Trace from fan/limit switch back to blower to see if there is a relay there.
 

WorthFlorida

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Please clear this up. You had a heating forced air furnace and you just had a central air system installed, The A coil was installed above the plenum on this furnace. How did the tech test the AC? Was it agreed that you do the wiring?
 
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