Air conditioning vacuum canister plumbing

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Animal Lawyer

Well-known member
Sep 3, 2020
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Ok so after replacing the hoses and valves etc on the engine side my a/c was not getting the car cold. I went to test the vacuum control system (as set forth in the service manual, and after running the car and turning it to acc the vacuum gauge went immediately to zero. When I got the car the canister was not connected and I attached the 2 hoses in what seemed the correct configuration (the larger engine vacuum line to the larger port and the smaller line (going to the ac control panel to the smaller port. However, after removing the old canister I realized none of the vacuum lines were original and that may not be correct.

1. Does anyone know which port the engine vacuum is supposed to go to (in other words, did I screw it up?) and 2. it is my understanding there is supposed to be a one way valve built into the canister, is there and if so, which port is it on and in which direction does it work (I am assuming it is on the engine vacuum side and prevents air from re-entering the canister when the vacuum on the line drops (thus keeping the canister "charged" to provide vacuum to the control even when the engine is not producing vacuum)

I'm hoping to troubleshoot the vacuum part of the system myself rather than paying my mechanic the hours to do it (I believe I am capable of setting the controls as instructed by the service manual, turning the car from run to acc and reading the gauge) 

Finally, on the right side of the control panel (behind the bezel) there are 2 electrical connectors, which color wires go to each position (as I moved the bezel to snake wires for the stereo install the 2 connectors came loose, I blindly reconnected them and the heater/defrost functions all seem to work well (at least when the car is idling and vacuum is high) but I want to assure myself that I did not cause the a/c issues by doing something stupid (like reversing the 2 plugs).

Thanks in advance. 


If these are the green/purple wires, it doesn't matter at all which wire goes onto the two pins.  Ford was very good to ensure that one couldn't screw up electrical connections: gender-oriented plugs, and when plugs didn't matter, you could go either way without harm.