The A/C hasn't worked since I got the pickup a few years ago. We've decided to use it as a family car but we have to get the A/C working (we're in Texas...). The other day I was checking it. On A/C and Max A/C the clutch wouldn't engage. Today I tried it and the clutch would engage, then click off, at regular intervals. It would run about 5-10 seconds, disengage, and after about 30 seconds it would reengage. It did this consistently.

Is this engage/disengage a specific symptom of something? Has anyone ever heard of it doing this/

Either way I'm thinking I'm going to have to replace it. And of course it's 100+* outside.

 

Need gauge readings...

 

Beats me. I can't even get gauge readings. They won't attach to the proper ports. Now I have to take these $115 gauge set back to the store for a refund. The compressor is turning on and off several times within a minute. The air is blowing hot out of the vents. You tell me.

 

well IMHO its low on pressure..if it's not then look at the pressure switch...

 

IMHO, it's high pressure. Can't tell for certain without gauges. That's why they make gauges - removes the guesswork.

If it were low on charge, it would be short cycling on both the engaged and disengaged time intervals. If it's cycling due to excessive discharge pressure, it takes more time for that pressure to drop from around 450 psi to 260 psi yielding a longer off time. If it's doing this, the hard line between the compressor manifold and the condenser will be extremely hot - hot enough to burn skin.

R134a fittings are standardized on all vehicles and compatible manifold gauge sets. They should fit unless they're defective or they're the wrong ones... or you got the low and high pressure ports wrong.

 

Well I probably shouldn't have had a few when I was trying to use the gauges and when I typed my smart a$$ reply.

Hooked the gauges up fine, let the system stabilized, and this is what I got:

High pressure: Compressor engages at 95, gets up to 128, then cycles off.
Lo press: When the high is at 95, the low is at 45. When the compressor is running the low press drops to about 20.
Once the compressor turns off the high side drops from 128 back to 95, and the low side raises from 20 to 45.

Turned off the system and both gauges showed 60. Bubble test showed no leaks at any of the visual lines or joints.

Later update:

Drove it 10 miles. Air was barely cool but not enough to cool the interior. Whenever I'd give it gas, say to get up a hill, the air would stop blowing out of the vents and blow out the floor or windshield. When I'd let off the gas, after about 30 sec it would switch back to vent. Got it back home and the gauges were reading 35 on low and 215 on high.

Added refrigerant to 180 on the high side. Now the compressor stays on, compresses for a while, then turns off. It fluctuates less but still 20 psi on both sides . But: the air is not cold. Line from compressor to evaporator is hot. Line from the accumulator to the compressor is lukewarm but becomes warmer.

I'm thinking a faulty pressure switch (as someone suggested) and possibly the condenser fins are clogged (extremely likely due to the age and farm environment).