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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 7743
Experience:  Furnace, A/C and heat pump specialist.
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I have a coldflow ac unit and I'm trying to find out where

Customer Question

Hello I have a coldflow ac unit and I'm trying to find out where to connect my c wire
JA: Did you double-check the thermostat? And what about the unit's filters?
Customer: I am replacing the thermostat that requires a c wire
JA: Do you plan on doing the work yourself?
Customer: Yes
JA: Anything else we should know to help you best?
Customer: No
Submitted: 3 months ago.
Category: HVAC
Expert:  airheatman replied 3 months ago.

Do you have model on the indoor unit? The transformer will have two low voltage wires.One is considered "HOT" and goes to R at thermostat.he other is COMMON.C at thermostat will go to that wire.

Do not rate until we are finished.

Customer: replied 3 months ago.
Here is a picture of the plate
Expert:  airheatman replied 3 months ago.

Looks like Coldflo has there wiring diagrams and manuals protected.Do you see a wiring diagram you can send a picture of?

Customer: replied 3 months ago.
Here is a pic
Expert:  airheatman replied 3 months ago.

Excellent .Thanks for the picture.

As noted, there are 2 low voltage wires coming from transformer. One goes to R at thermostat.The other is your C wire. It will go to C at thermostat and all components (Contactor,fan relay,timer ,etc)

Customer: replied 3 months ago.
Ok but I don't see where I can connect a "c" wire
Expert:  airheatman replied 3 months ago.

Pic gets a little blurry when I enlarge it. Look closely at the transformer and tell me if you see 24v marked on thermostat label and if so which wires I picture go to the 24v terminals.

I am thinking 24v common is this yellow wire

Expert:  airheatman replied 3 months ago.

That should say marked on transformer not thermostat

Customer: replied 3 months ago.
The yellow goes to a terminal that says "common "
Customer: replied 3 months ago.
I'm sending you a pic
Expert:  airheatman replied 3 months ago.

That should be your 24v common. Do you have a volt meter?

Customer: replied 3 months ago.
I do not. But when I do hook up my " c" wire to that, the thermostat turns on and off.....5 sec on and then 10 sec off 5 sec on and then 10 sec off and so on
Expert:  airheatman replied 3 months ago.

Not sure why it would be going on and off. WE should have constant 24v

Customer: replied 3 months ago.
correct that is what I've been reading. The ac works fine with the old battery powered unit. Just trying to add a "c" wire that I see was never hooked up
Expert:  airheatman replied 3 months ago.

If you can get a meter we can try to troubleshoot to see where it may be coming and going and what is breaking the circuit like that

Customer: replied 3 months ago.
Ok I will get one in the morning and will reply to you then 11:35 eastern.... All hardware stores are closed now
Expert:  airheatman replied 3 months ago.

Sounds good.Talk to you tomorrow.

Customer: replied 3 months ago.
Ok thanks.
Expert:  airheatman replied 3 months ago.

Thanks for letting me work with you.

Customer: replied 3 months ago.
Good morning. I have a voltage meter now.
Expert:  airheatman replied 3 months ago.

Excellent. Lets start by going to thermostat and putting one lead on C and one on R and make sure we are losing the 24v after 5 seconds.If so we wlil go back to air handler

Customer: replied 3 months ago.
Not loosing. Voltage does not drop
Customer: replied 3 months ago.
When compressor turns on I loose my voltage
Expert:  airheatman replied 3 months ago.

I would replace that transformer.It sounds like it is bleeding down under load.Make sure to use at least a 40VA transformer.

Customer: replied 3 months ago.
Ok. Can you tell me what the transformer looks like?