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Old 07-22-2020, 10:49 PM   #1
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Carrier A/C wiring diagram

Picked up my first bus today and noticed the rear A/C was blowing hot. Did some investigating and found a pressure switch wiring appears to be damaged and could be the reason why it doesn't work. Problem is I have no clue where this wire could go or if it has been bypassed.. Does anyone know where it should go or have a wiring diagram for the pressure switches on a factory carrier A/C? I searched and found an installation instructions but this doesn't show the wiring for the pressure switches. Any help is greatly appreciated.
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Old 07-23-2020, 12:22 AM   #2
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Originally Posted by rider5000 View Post
Picked up my first bus today and noticed the rear A/C was blowing hot. Did some investigating and found a pressure switch wiring appears to be damaged and could be the reason why it doesn't work. Problem is I have no clue where this wire could go or if it has been bypassed.. Does anyone know where it should go or have a wiring diagram for the pressure switches on a factory carrier A/C? I searched and found an installation instructions but this doesn't show the wiring for the pressure switches. Any help is greatly appreciated.
I would not bypass the switch. Do you know what model your A/C is? I was able to find a complete manual for my carrier system on the internet. It included wiring diagrams. Posting some pics of your A/C system would be helpful to find out what model it is.

Also where does that line with the sensor go?

Ted
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Old 07-23-2020, 11:28 AM   #3
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I'll snap some pics in a bit and find out what model it is. I wasn't saying that I want to bypass the switch, just that it may be bypassed and from what I can tell it is already. Looks like it is the LP switch and checking it with a meter it's closed which is good and has refrigerant in the lines. Also looking at my second unit there is a signal wire coming off TB6 then goes through both pressure switches then to the compressor, all in series. With my bad unit the wire comes off TB6 then through the HP switch and to the compressor, so the LP switch is bypassed and I'll have to fix that, but now I don't thing the pressure switch is my problem. I was spinning the compressors by hand and one is smooth while the other has a lot of resistance and feels like it is grinding. Anyone know what these should feel like normally when spinning by hand?
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Old 07-23-2020, 01:50 PM   #4
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the one thats spinning too freely may be low on freon.. im used to them having a decent resistance when they are full.. you can test run the units by themselves and see if both compressors engage.. you wont destroy the system from low freon if you start the compressor for a minute or so to check it...
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Old 07-23-2020, 09:52 PM   #5
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Thanks for the info cadillackid and I think your correct. I also found another interesting thing. I have 3 units interior units, the rear and middle are apart of one system. The front unit is the second system. For some reason when I turn the front unit, both the compressors engage and when I turn on the middle or rear unit, neither compressors engage. I think someone tied the signal to turn on both compressors to the front switch. If I unhook the compressor on the right, the front unit (the working one) stops blowing cold so that compressor is working. I may need to buy a set of gauges and check the pressure on the left side and see if is low or a bad compressor, which I'm thinking a bad compressor since that side has the HP, LP switch inline with the compressor signal. Also need to figure out why the units are tied together. A wire diagram would be really helpfull right now.
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Old 10-07-2020, 08:04 PM   #6
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Thanks for the info cadillackid and I think your correct. I also found another interesting thing. I have 3 units interior units, the rear and middle are apart of one system. The front unit is the second system. For some reason when I turn the front unit, both the compressors engage and when I turn on the middle or rear unit, neither compressors engage. I think someone tied the signal to turn on both compressors to the front switch. If I unhook the compressor on the right, the front unit (the working one) stops blowing cold so that compressor is working. I may need to buy a set of gauges and check the pressure on the left side and see if is low or a bad compressor, which I'm thinking a bad compressor since that side has the HP, LP switch inline with the compressor signal. Also need to figure out why the units are tied together. A wire diagram would be really helpfull right now.

I called transartic in South Georgia and Dale walked me through all of the wiring and sent over a diagram. 1-877coldair
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