air conditioning only runs for about a minute!

[doehunter]

Hi again,
'93 Explorer, 6 cyl. stock.
Ac blows cold for about a minute then gets hot. I looked and the compressor is not running. Things I did to troubleshoot:
1. I hot wired the compressor it so it would stay running for checking it out.
2. I checked the low side pressure and it's about 45 psi.
3. pulled the hot wire off.
4. check voltage with clutch wires disconnected, 14 volts.
5. check voltage with clutch wires connected, 0 volts.
6. Idle speeds up when I connect the clutch wires.
I'm an AC retard, but I'm hoping this will give you enough information to help me help myself! I really don't know how it all works.
thanks,
Jim

 

[Iron Weasel]

R-12 or R-134a?

Is the compressor clutch engaging then disengaging in a cyclic manner every few seconds or is it just not running at all?

 

[doehunter]

R-12 or R-134a?

Is the compressor clutch engaging then disengaging in a cyclic manner every few seconds or is it just not running at all?

No, well not really. I runs constant for a few seconds, then cycles, then stops running altogether. I have heard the cycling on/off indicates low refrigerant pressure. I checked the low side ( only have the one gage on a freon can) and it's good.

 

[Roadrunner777]

I'd get into a chiltons manual or autozone, see what's driving the clutch. I think there are a couple of pressure switches. But, it's not a huge jump to say that the system probably leaked down and needs a can of freon. I'm not an AC person either. When mine goes out, I'll probably just pull it all and convert to heat only.

 

[doehunter]

R-12 or R-134a?
R134A

Is the compressor clutch engaging then disengaging in a cyclic manner every few seconds or is it just not running at all?

 

[Iron Weasel]

Typically, if the system is above 25psi, then the clutch will engage and run until the pressure in the system hits 25psi then it'll shut off. For example, if you have a static (engine idling with A/C off) pressure of 45psi, the clutch will engage until the pressure drops to 25psi, then the clutch will disengage until the pressure builds back up to 45psi.

Hook your gauge up, start the engine then note the static pressure. Have someone else turn the A/C on while you continue to watch the gauge. If it drops below 25psi, then the clutch should disengage which results in warm air. Normally, the A/C system is closed, so if you're low on refrigerant and you haven't intentionally opened the system then chances are you have a leak.

 

[wood1]

Pretty sure Glacier went into great detail on how to work on the 1st gen air/con system. Do a search. BB is a wiz with that stuff too.

 

[jimpl]

Typically, if the system is above 25psi, then the clutch will engage and run until the pressure in the system hits 25psi then it'll shut off. For example, if you have a static (engine idling with A/C off) pressure of 45psi, the clutch will engage until the pressure drops to 25psi, then the clutch will disengage until the pressure builds back up to 45psi.

Hook your gauge up, start the engine then note the static pressure. Have someone else turn the A/C on while you continue to watch the gauge. If it drops below 25psi, then the clutch should disengage which results in warm air. Normally, the A/C system is closed, so if you're low on refrigerant and you haven't intentionally opened the system then chances are you have a leak.

I was checking the pressure with the ac running. That's why I wired the clutch direct to the battery, so I could do that. The pressure is good. In fact it was a little high and I let some out to get to 45 psi.
My son suggested it might be a pressure switch, but had no ideas on how to test.

 

[jimpl]

Pretty sure Glacier went into great detail on how to work on the 1st gen air/con system. Do a search. BB is a wiz with that stuff too.

Glacier as in on this site? OK I'll look.

 

[Nomad767]

I would def go to harbor freight and buy some cheap gauges. Much better to look at an a/c system with both the high and low pressure info. Without that, you are just assuming everything is running perfect when you know there is an issue somewhere. The easiest way to check the pressure sensor would be to jumper the plug for it. That will keep you compressor running constantly with no cycling from low pressure. But without some good gauges, i would not recommend playing around with anything since you don't know what the complete system pressures are.

 

[jimpl]

Pretty sure Glacier went into great detail on how to work on the 1st gen air/con system. Do a search. BB is a wiz with that stuff too.

OK I'm feeling like a moron now. I've been trying ti use the search thing, and I'm just getting frustrated. I can find a ton of stuff that doesn't apply, but nothing to help me.
A coworker offered to bring in his gage set today and I want to know what the pressures should be on high and low sides when it's running, but I can't find it.
Help?

 

[Iron Weasel]

High side pressure should be about 2.2 - 2.5 times the ambient air temperature. Keep in mind that this is a guideline and not an absolute.

So if it's 82 degrees outside, high side pressure should be 180psi - 205psi.

 

[jimpl]

High side pressure should be about 2.2 - 2.5 times the ambient air temperature. Keep in mind that this is a guideline and not an absolute.

So if it's 82 degrees outside, high side pressure should be 180psi - 205psi.

Thank you so very much.
This is even better than what I was looking for.
I'll go check it out now.

 

[jimpl]

My pressures were good. I bypassed the low pressure switch, and it worked good.
Hit the parts store, got the switch in, and now I can relax!
thanks guys.
Jim