No, the blend doors do not activate the a/c compressor clutch, but, freon in the system does allow it to activate when it is switched on. So, if the system is empty the clutch will not activate. So, you'll need to start by hooking up some a/c gauges to see if the system has enough freon to operate.

 

No, the blend doors do not activate the a/c compressor clutch, but, freon in the system does allow it to activate when it is switched on. So, if the system is empty the clutch will not activate. So, you'll need to start by hooking up some a/c gauges to see if the system has enough freon to operate.

The system has plenty of refrigerant. I put a set of gauges on it and it has adequate pressure, but the compressor is not engaging. What would create heated air to come out of the vents when the temperature control is set to low and the AC is set to on or the AC is off and I'm trying to pull in fresh outside air that is currently 50° ?

I'm not familiar with AC system sequence of operation persa, what holds the compressor out due to another system component being energized or an end switch etc.

I'm sure there is some sequence of operation. Is the engine cooling fan commanded on when the AC is on?

Thanks

 

I always start by putting a can of freon in as the compressor not engaging is the classic sign of low freon.

 

Yea, over charging is not something I'm apted to do. I always recover the refrigerant, leak check, pull a vacuum and weigh in the factory specific amount of refrigerant. I definitely don't perform the guessing game. An over charged system is just a bad as an under charged system.

 

The a/c compressor will still operate even on full hot in these vehicles. You should probably check to see if you have 12v to the clutch field coil. A few here have replaced the a/c clutch due to non-operation.

 

So there is nothing that will hold the compressor out, safety, nothing?

 

You mean like a pressure switch? You said it had enough freon. From there you've got whatever switches it on in the HVAC controller AFAIK(don't ask me how to diagnose that).

 

Yup, plenty of refrigerant. I'm going to put a scope on it and actuate the compressor along with everything else in the AC system. Blowing heated air when it's calling for cooling has me puzzled. I'll find out soon enough. My buddy owns a high end shop, but he's out of town until Monday. The suspense is killing me. I'm a technology fella, but darn there is a tremendous amount of computers in that truck.

 

Yup, plenty of refrigerant. I'm going to put a scope on it and actuate the compressor along with everything else in the AC system. Blowing heated air when it's calling for cooling has me puzzled. I'll find out soon enough. My buddy owns a high end shop, but he's out of town until Monday. The suspense is killing me. I'm a technology fella, but darn there is a tremendous amount of computers in that truck.

Yeah, that's to de-humidify the air.

 

I have the entire wiring diagram for the vehicle , there is not a humidistat or humidity sensor in the climate control system. Air conditioning lowers the dew point by removing the moisture in the air, the heat does not. You can have humid 140° air. The higher the dew point the more moisture there is in the air.

 

Yup. That's why the compressor is always engaged. Temperature is regulated by the blend/mix/temp doors.

On a Pontiac Solstice, the a/c compressor never disengages, even with the system off. It only disengages when the engine is shut off and also under full throttle. It's a GM thing, I think.

 

A buddy had one of those POS and every time he'd pull out on the freeway the darn AC would shut off unti he came off the throttle.

I have the entire schematic for the SRX it definitely cycles. You can see the different components that cycle the compressor upon cooling temperature demand and in defrost mode.
The compressor is a variable displacement, not fixed.

 

A buddy had one of those POS and every time he'd pull out on the freeway the darn AC would shut off unti he came off the throttle.

I have the entire schematic for the SRX it definitely cycles. You can see the different components that cycle the compressor upon cooling temperature demand and in defrost mode.
The compressor is a variable displacement, not fixed.

Oh, I never meant to say that it doesn't cycle, I know that it has to to prevent freezing up. But, it doesn't cycle as a temperature adjustment, the blend doors do that.

 

It was always my understanding that a variable displacement compressor doesn't cycle and fixed does. But, I'm not looking at a manual. I could have it backwards. I'm just going off of memory and I've been retired a few years now.

 

I don't work on cars except my own LOL 😂. The fixed displacement compressor is designed for constant cycle, even strokes within the refrigerant system. Fixed displacement reaks havoc on the fella that likes to overcharge his AC system. I'm new to this Cadillac stuff, but I work on everything from my cars/ trucks to heavy equipment Hvac systems. Who wants to pay when you can repair it yourself.

 

Hey, I'm no expert, but this isn't rocket science. If your compressor doesn't engage it likely is low on freon. I don't use gauges to charge, I've done enough cars to have a good feel for it. I put a thermometer in the center vent and feel the lines with my hands to judge what's going on. When I see the temp drop I'm looking for I call it good and stop charging. Also my compressor cycles, sucker is loud and these cars. How can there be any doubt? You can tell 50 yards away it's cycling.

 

If you read my post there are two issues. 1) no compressor, 2) heat on when in cooling mode. With the technology today the feel the pipe and watch the condensate drip doesn't cut it. I prefer pulling the charge and weighing in the exact amount of refrigerant per the manufacturer specs. It's not like the systems grow and they need extra refrigerant. If you're adding refrigerant, you have a leak and it must be fixed. My issue is definitely not refrigerant related nor clutch issue. I'll conclude my venture once I put a scope on it.

 

If you read my post there are two issues. 1) no compressor, 2) heat on when in cooling mode. With the technology today the feel the pipe and watch the condensate drip doesn't cut it. I prefer pulling the charge and weighing in the exact amount of refrigerant per the manufacturer specs. It's not like the systems grow and they need extra refrigerant. If you're adding refrigerant, you have a leak and it must be fixed. My issue is definitely not refrigerant related nor clutch issue. I'll conclude my venture once I put a scope on it.

Please do. I'd like to know what it ends up being.