Scan Tool for Intermittent A/C Problem

[Servo]

Hi All,

 

I'm currently having an intermittent problem with my air conditioning system. Sometimes at idle or during downhill coasting my AC shuts off, and the temperature rises until the air coming out of the vents is at ambient.

 

Since the problem is intermittent I need a scan tool that I can use while driving around. Does anyone have any good recommendations for a scan tool? My basic tool does not give me the enhanced data that I need, and really didn't want to buy a $3000 Snap On model.

 

Thanks for all help!

Ken

[Chris]

Depending on your year, you could locate a tech 2. It wont be that cheap

[00Silverado4x4]

Just for giggles of it, have you check your refrigerant charge level?

[Servo]

I've had the gauges on when the system is working normally, and everything looked fine here. I have a thermometer in the air vent, and I can watch the temperature go from a cool 45 degrees while driving around up to 80 or 90 degrees when I get to a stop light. But this is only sometimes because the problem is intermittent.

 

I know that the clutch is not engaged when I have this problem, and I know that the low pressure switch is not the problem. Beyond that I have not been able to consistently probe around while the problem is occurring. Hence the need for a scan tool.

 

Based on the previous suggestion, I have seen Tech2 scanners go from $320 up to $1500. If I were to go the cheaper route would I still get all the functionality?

 

Thanks,

Ken

[Duelin]

What type of vehicle and type of A/C unit are you trying to diag.? The Tech ll scanners that cost $320-$1500 are Chinese knock offs. Unless they are used. A dealer based Tech ll Will cost between $3500 and $5000 depending on what is loaded on it.

[txab]

Have you checked the air gap on the clutch? As it wears, the gap can widen and it may not pull in when commanded or it may disengage prematurely.

[Servo]

It's a 1999 GMC Sierra 4WD with the Z71 package. It is very frustrating that scanners cost so much because everything is tied into the VCM.

 

I'll check the gap, but the compressor was replaced about two years ago.

 

Thanks,

Ken

[Duelin]

If your model has vacuum operated blend doors you could have a vacuum leak or a leaking vacuum tank. With the vacuum type units you have a vacuum tank so you have a reservoir of vacuum. The tank is needed for low vacuum conditions. If you don't have that reserve vacuum to keep the doors in position they can move in the opposite direction blocking off the cool air. And on some units letting hot air to start flowing thru the system.

[2016 Sierra Owner]

I'd check the radiator fan clutch as well. It sounds like the fan is not engaging at the red light to pull air through the radiator while you are stopped. Is the engine getting hot as well?

[MikeNH]

My 2003 used to do the same exact thing at stop lights and such. Never could figure out what was wrong. GM had a TSB to add an auxiliary e-fan on 6 liter vehicles for the same issue but it didn't issue one for the other engines.