No A/C in '97 Ranger - please advise

[aweiss2k]

Long story short, with the A/C on full blast in my '97 Ranger, warm air comes out. After the blend door fix, everything worked great until I left the truck with a friend for 12 months while I was abroad and it just sat.

With a pressure gauge hooked up to the low-pressure port, the PSI fluctuates on a (roughly) 10 second cycle. It starts at 35 PSI and builds over 6-8 seconds up to about 60 PSI, then the A/C clutch kicks in for 2 seconds and the pressure drops back to 35 PSI and begins building again.

Is this is a sign that the pressure is too low? Too high (not sure how that could be...)? Any ideas what's going on here? Where should I be looking for problems?

Thanks,
Aaron

 

[shadetree]

Sounds as if it is low on freon. What is the high side reading? What is the reading with the engine off?shady

 

[aweiss2k]

Thanks for the reply. Unfortunately, I don't have a manifold gauge set to check the high side.

Is 35PSI low enough to activate the low-pressure cutoff switch and cause the compressor to disengage?? Should I short the switch or put enough new freon in the system to get the compressor to kick in? How much pressure on the low end can the system handle?

Thx,
A

 

[KELLY88]

My 97 was doing what you described. I had (and still have) a leak in the system. Take it to a shop. A lot of them are doing cheap A/C system tests. They'll tell you where the problem lies and you can go from there.

 

[shadetree]

Thanks for the reply. Unfortunately, I don't have a manifold gauge set to check the high side.

Is 35PSI low enough to activate the low-pressure cutoff switch and cause the compressor to disengage?? Should I short the switch or put enough new freon in the system to get the compressor to kick in? How much pressure on the low end can the system handle?

Thx,
A

It will handle 25lbs on the low side ok.shady

 

[Dweano]

I wish i had AC to cause me problems...darn base ac free base model lol

 

[aweiss2k]

turns out...not so bad

After reading more about how the A/C systems works (and eying a manifold gauge set and vacuum pump from Harbor Freight) it seemed to me that the problem was the low-side sensor. The compressor would kick in every time the low-side got above 55PSI (exactly) and then kick off below an exact threshold. So, I decided the bypass the sensor and connect the wires directly.

Just as I was about to cut the wires, I noticed that - somehow - one of them had already been cut (torn) about 90% of the way through! After cutting the damaged part out and repairing the wire (and adding about a can of new refrigerant), everything works fine.

I suppose there must be a gradual leak somewhere, but the system seems to be holding pressure fine now, so I'm not worried about it.

Thanks for all the help.

Cheers,
Aaron