No voltage ac compressor plug

[Jesseyourcalipers]

2010 Chevy Malibu 4cyl 2.4l. Girlfriends Ac not blowing cold. No voltage at the plug. Checked with ground and positive finder. Ground lights green, no red light though can’t find current. Tried voltage meter and even put needles in the wires directly same thing. Tried all combinations of key ok ac on car on car off. No voltage at the green wire. Clutch engages when tested from direct power supply. System is fully charged. Possibly over charged a bit. Fuses are all good relays were changed. Question is can a pressure switch on the pressure line cause no voltage at the plug with key and ac on engine off? I know the switch can cause an ac compressor to not turn on but I thought it was pressure that makes it do its job. Any thought greatly appreciated from a dummy DIYer

 

[zrxkawboy]

Question is can a pressure switch on the pressure line cause no voltage at the plug with key and ac on engine off?

The clutch will not be powered with the engine off.

 

[Nukeman7]

Odds are high that if the refrigerant charge is normal, the low pressure switch is good. They typically fail by losing their seal and leaking refrigerant. Personally, I have never seen one that failed electrically. You can easily test it for continuity with a multimeter.

 

[Jesseyourcalipers]

The clutch will not be powered with the engine off.

Odds are high that if the refrigerant charge is normal, the low pressure switch is good. They typically fail by losing their seal and leaking refrigerant. Personally, I have never seen one that failed electrically. You can easily test it for continuity with a multimeter.

my dad did that looks good I also found it hard to believe it would fail electronically

 

[mk378]

This car has a sensor on the high side line, not a switch. The sensor is connected to the ECM and probably can be read as live data with a scanner. If the ECM sees the pressure is within the acceptable range, the engine is running at acceptable rpm, and the control panel is calling for A/C, the ECM pulls in the compressor relay.

 

[FowVay]

Fiddle with the A/C clutch relay in the fuse box under the hood. There's a fuse and a relay that you should check out just for the fun of it. See if power is making it to the relay. If it is then try jumping the relay to see if it is the problem. If it proves to be in working order then that's one less thing to consider and easy to isolate.

 

[brages]

Personally, I have never seen one that failed electrically. You can easily test it for continuity with a multimeter.

I had a pressure switch fail electrically on my Ranger

 

[berniedd]

Just last month, the Ford's aircon wasn't cooling the air. I checked what I could at home: circuit fuse ok, power relay to the aircon circuit ok. I thought maybe low on refrigerant? Brought it to the shop, they attached their gauges. Nope, system's full. They found the problem to be a failed pressure switch that didn't allow power to get to the compressor (original to the car, 15 yrs old).

 

[Marcozi]

Even cars of that vintage have computerized climate control modules (CCM). Before the module activates the compressor clutch several conditions have to be met:
- the engine computer signals the CCM that it's ok to engage the clutch
- the refrigerant pressure has to be within range
- the outside temperature is above a specific value
- the electric engine fan had to have passed the start up test
- system voltage is within range
- the CCM had to have passed the start up test