Ac working intermittently

[French02chris]

Hi
Today my ac was acting up...
I started to drive on the highway , put the ac in low setting (always do low setting) and cold air was fine..
Stopped at Walmart, got back to interstate, put ac on... Only warm air coming in..
Turned off the ac, drive a few minutes with open sunroof, then tried ac again : back to cld air!!
Stopped somewhere else, then same thing happened!!!! Warm air, then after turning ac on and off a few times : cold air!!!
What could it be???
(good thing we are getting in lower temperature in North Florida now.. Lol)

 

[Jlaa]

Hi
Today my ac was acting up...
I started to drive on the highway , put the ac in low setting (always do low setting) and cold air was fine..
Stopped at Walmart, got back to interstate, put ac on... Only warm air coming in..
Turned off the ac, drive a few minutes with open sunroof, then tried ac again : back to cld air!!
Stopped somewhere else, then same thing happened!!!! Warm air, then after turning ac on and off a few times : cold air!!!
What could it be???
(good thing we are getting in lower temperature in North Florida now.. Lol)

Some years ago I had an intermittent issue with the AC compressor not engaging.
I was going to look into it, but got sidetracked as I then replaced by original upper wiring harness first.
That was years ago. Since replacing the upper wiring harness, my AC compressor issue went away.

Is your upper wiring harness updated? (just thinking about getting everything to a known-good state first before further troubleshooting)

 

[French02chris]

Some years ago I had an intermittent issue with the AC compressor not engaging.
I was going to look into it, but got sidetracked as I then replaced by original upper wiring harness first.
That was years ago. Since replacing the upper wiring harness, my AC compressor issue went away.

Is your upper wiring harness updated? (just thinking about getting everything to a known-good state first before further troubleshooting)

That thing has been replaced years ago.. I have been driving that car for almost 8 now.. Lol
I got 344k miles on it
Compressor was replaced a couple years ago

 

[gerryvz]

Likely you have low refrigerant in the system, which is not triggering the pressure switch to turn on the compressor. Probably based in part on ambient temp.

Put some gauges on the system (high and low side) and see what the pressures are, particularly on the low side. You may just need a bit of a recharge.

That said, if you need a recharge, and you just replaced your compressor a couple of years ago, you also may have a leak in the system somwehere. You can get R-134 (if your refrigerant does prove to be low) with UV dye already in it, so that you can identify where any leak would be a bit down the road using a black light and special glasses. You can get the black light and glasses at any AutoZone or said "McFLAPS" type auto parts store (or Amazon).

Another thing you can do immediately is to jumper the pressure switch and see if that turns the compressor on. If so, then you also have a pretty good idea that either you don't have enough pressure (refrigerant) in the system, or you have a bad pressure switch.

Other things to check after you ascertain refrigerant condition and whether there's a leak:

1) electrical connection at the compressor
2) Base Module (GM) in the CAN box

 

[French02chris]

Likely you have low refrigerant in the system, which is not triggering the pressure switch to turn on the compressor. Probably based in part on ambient temp.

Put some gauges on the system (high and low side) and see what the pressures are, particularly on the low side. You may just need a bit of a recharge.

That said, if you need a recharge, and you just replaced your compressor a couple of years ago, you also may have a leak in the system somwehere. You can get R-134 (if your refrigerant does prove to be low) with UV dye already in it, so that you can identify where any leak would be a bit down the road using a black light and special glasses. You can get the black light and glasses at any AutoZone or said "McFLAPS" type auto parts store (or Amazon).

Another thing you can do immediately is to jumper the pressure switch and see if that turns the compressor on. If so, then you also have a pretty good idea that either you don't have enough pressure (refrigerant) in the system, or you have a bad pressure switch.

Other things to check after you ascertain refrigerant condition and whether there's a leak:

1) electrical connection at the compressor
2) Base Module (GM) in the CAN box

Since it has been 2 weeks now, and a round trip from Florida to Cape Cod, I decided to give an update
Ac is working fine!! The problem never came back!!! So, probably a glitch in the matrix!! Lol
I tried to turn off & on the ac numerous times while driving, but the issue never came back..

 

[jhodg5ck]

Good to hear, FWIW the speed sensors can become intermittant as well. If it's not working again try a quick restart and see what happens.

43 degrees this moring in the ATL. No ac required ;-)

 

[maw1124]

Did you ever replace your pressure switch? I've had 2 intermittent A/C issues. One was that switch and the other was a failing tensioner.

maw

 

[Black 034]

I need correct wiring for AC compressor 3 prong plug. I have seen 1-white, 2 red,3 Blue and also 1 red, 2 white, 3 blue or does it not matter on red and white since they go to speed sensor?

 

[gsxr]

Shouldn't matter if speed sensor wires are reversed, AFAIK.

FSM schematic at this link, screenshot below. Wire colors are for the chassis harness, not the compressor itself.

1 = Red/Blue (sensor)
2 = White/Blue (sensor)
3 = Blue/Green (clutch)

 

[Black 034]

I will go with that thanks alot!