AC help, please

[yotermanic]

So...my wife's Suburban's AC is making me look like an idiot. It's a 1997, 5.7L, Dual AC (front/rear).

Compressor wouldn't kick on, hit it with a UV light, no dye. Checked charge, empty, added refrigerant/dye, compressor glowed like a christmas light. Changed compressor/orifice/drier, everything works great all the way home.

Next day, wife says no AC. Hook up gauges, static pressure fine. Hit AC button, no light, no compressor. Check voltage into Heat/AC module, good. Check voltage out on light green wire to pressure switch/module, nothing. Order control head, put it in, everything works great and I'm looking like a champ.

Next day, wife says no AC. Check voltage to low pressure switch, nothing. Check voltage in adn out of control head, good voltage in, nothing out. Surely this control head couldn't have gone bad this soon? I checked the AC interrupt circuit from the blower selector and it seems to be operating as it should. Any of you gurus seen this?

I admit, I was a Ford mechanic so I don't have any in-depth knowledge as to how this control operates, are there other inputs that could shut down the system at the control head? I have a chilton's wiring diagram and its, well, er... you guys know. Any good input would be greatly appreciated.

Also, how stout is the low pressure switch? I am debating jumping the relay, running it through the switch, then to the compressor to get her up and going, it's been over 100 here and she drives my kiddos around. I would just jump the relay, but don't want her to drop pressure too low getting on the highway or something.

[MT-2500]

Only jump relay for testing.
It is a Good test for compressor clutch and circuit.

Some info on ac circuit.

The Ac circuit runs threw a lot of stuff.
Starting with 3 under hood fuses.
AC Maxi and IGN Mini and AC compressor fuse.
Also Ac comp fuse in IP panel.
But that is only the beging of circuit to compresser.
First is the AC control module and the VCM/PCM computer.
And then 3 pressure switches.
AC low and AC high and ac compressor switch aqnd relay.
Then if the cluctch signal/voltage gets threw all of that the ac cluch and coil and plug-in and wiring has to be good.

I would start with a jumper compressor clutch and make sure it works and check for lose of charge.
What is the low and high side readings with compressor jumped?

If good.
You will need to get a wiring diagram and a volt meter and start at beging of AC circuit and work threw it.
Also check wiring and plugins real close.

A good AC HAVC capable scanner reads out a lot of the stuff on AC circuit and aids in finding the problem are.
It usually shows AC pressure readings and AC compressor request threw computer and so on.

[j cAT]

Originally Posted by yotermanic

So...my wife's Suburban's AC is making me look like an idiot. It's a 1997, 5.7L, Dual AC (front/rear).

Compressor wouldn't kick on, hit it with a UV light, no dye. Checked charge, empty, added refrigerant/dye, compressor glowed like a christmas light. Changed compressor/orifice/drier, everything works great all the way home.

Next day, wife says no AC. Hook up gauges, static pressure fine. Hit AC button, no light, no compressor. Check voltage into Heat/AC module, good. Check voltage out on light green wire to pressure switch/module, nothing. Order control head, put it in, everything works great and I'm looking like a champ.

Next day, wife says no AC. Check voltage to low pressure switch, nothing. Check voltage in adn out of control head, good voltage in, nothing out. Surely this control head couldn't have gone bad this soon? I checked the AC interrupt circuit from the blower selector and it seems to be operating as it should. Any of you gurus seen this?

I admit, I was a Ford mechanic so I don't have any in-depth knowledge as to how this control operates, are there other inputs that could shut down the system at the control head? I have a chilton's wiring diagram and its, well, er... you guys know. Any good input would be greatly appreciated.

Also, how stout is the low pressure switch? I am debating jumping the relay, running it through the switch, then to the compressor to get her up and going, it's been over 100 here and she drives my kiddos around. I would just jump the relay, but don't want her to drop pressure too low getting on the highway or something.

get a wiring diagram for your vehicle and you should be able to find out whats going on..make sure the electrical grounds are clean and secure. to many electrical problems this is usually a ground issue ..need wiring diagram.

[yotermanic]

Anybody know where to get a good wiring diagram for this short of buying the manufacturer's manual? I KNOW with a good diagram, I can sort this out.

A/C Pressure seems pretty good, static is around 120-130 and low side is about 28-32 with compressor jumped. Afraid my high side gauge is busted and with work being slow as it is, I am not sure I can pick up a new one in the near future.

[MT-2500]

Originally Posted by yotermanic

Anybody know where to get a good wiring diagram for this short of buying the manufacturer's manual? I KNOW with a good diagram, I can sort this out.

A/C Pressure seems pretty good, static is around 120-130 and low side is about 28-32 with compressor jumped. Afraid my high side gauge is busted and with work being slow as it is, I am not sure I can pick up a new one in the near future.

All-Data and Mitchell on demand both have a on line DIY repair program that has all of the repair information and wiring and repair flow charts and TSB and recalls.
Will run you 25-35 for a one car one year on line subcription.

Or one of the members here may be able to private e mail you one.
Sorry I can not because of copy right on my repair info.

Public libarys and schools and repair shops and dealer service departments have that info and can print you offf a wiring diagram.

On charging and checking AC system it is a must and saftey isue to have both low and high side gauge.
Check around a gage can be found on old recharge mainfolds.

Good luck and let us know how it goes.

[j cAT]

Originally Posted by yotermanic

Anybody know where to get a good wiring diagram for this short of buying the manufacturer's manual? I KNOW with a good diagram, I can sort this out.

A/C Pressure seems pretty good, static is around 120-130 and low side is about 28-32 with compressor jumped. Afraid my high side gauge is busted and with work being slow as it is, I am not sure I can pick up a new one in the near future.

you need the high side pressures read to troubleshoot the ac system. call local ac/heating suppliers for a gauge that can fit your guage manifold set. should be about 25.oo I think...