air conditioning diagnosis?

[AKBroncoII]

Is there a pressure switch on the AC system that keeps you from engaging the compressor clutch when the pressure gets too low? This is on a 91 explorer. I can't get power to my clutch and can't figure out why. Tired of not having AC and need to get it fixed.

Once I get it figured out, how hard is it to refill the system? My chiltons just says to take it to a qualified AC specialist.

 

[snoman6115]

check ur relay, replace it with like the wiper motor one or sumtina nd see if it works then

 

[4x4junkie]

If the pressure is too low, the pressure switch will not engage the compressor, yes (there is no relay).

Probably be a good idea to flush everything out and convert it to run on R-134a at the same time too (and replace any leaky components).

To refill it requires evacuating the system with a vacuum pump for ½ hour before admitting the specified quantity of refrigerant into it.

 

[AKBroncoII]

How do I evacuate the system with a vacuum pump? What is required to swap to R134A? Is there a way to pressurize the system to figure out where it's leaking before I have it filled or fill it myself? My guess currently is the pressure is too low and won't allow the clutch to engage. I need to do this as cheaply as possible.

 

[RobbieD]

Your guess is probably right on.

I wish that there was a cheap way to fix your air (I'm into "cheap" fixes myself, brother). But, if you can find a can or two of R12, it'll be expensive. And, you very most likely have a leak in the system, so it'll just be a temporary fix; plus, leaking R12 into the atmosphere ain't good. Honestly, saving up to do a correct R134a retrofit is the best thing you can do. Sorry.

So, I'll try to help you out, with your other questions:

Your low pressure switch is on the drier / accumulator. It can be temporarily jumpered, FOR TESTING ONLY.

A vacuum pump is connected to the system with a standard AC gauge set.

There are "sniffer" leak detectors, and there's dye that can be put into the system. Another method, is if the system will hold a vacuum, after it's evacuated (with the pump). However, the best method is the next point.

One added benefit of a correct conversion, is that all of the system's o-rings should be replaced. Thus a lot of times, the conversion will also correct the fault in a system that has leaked out.

The sticky post at the top of this forum is a good writeup by MAKG on doing the conversion. Basically, and simplified, it involves replacing the drier, replacing all of the o-rings, flushing the system's components, adding the correct amount of compatible oil and R134a refrigerant. Once you open the system, evaluate it for "black death" (trashed compressor) and if the orifice will be reusable (it's really better to just replace it).

Hope this helps some, and good luck.

 

[4x4junkie]

Yeah the orifice tube is like $3. Just replace it.

The A/C on my Ranger developed a leak where the factory rubber hose was crimped into the metal end fitting. Check for ANY oily residue around these fittings. If you find any, that hose will likely need to be replaced or repaired.
The compressor seals are another likely source of a leak. Again, look for any oily residue or dust collecting all over it.

 

[AKBroncoII]

The problem is I won't find any oil around the hoses. I completely washed EVERYTHING before I pulled the tranny and did the oil pan gasket. I just hate that the system doesn't work. Only thing on the truck that doesn't work is the AC. I doubt I would use it much but for resale I see it being a problem.

 

[RobbieD]

Only thing on the truck that doesn't work is the AC. I doubt I would use it much but for resale I see it being a problem.

It sounds like a nice truck except for the non-functioning AC. So on the other hand, an R134a conversion may be a recoverable investment, as it would enhance the resale value. If you're able to do the work yourself, the parts cost is not too bad.

 

[Earl43P]

So, you have no idea what's wrong with it.

Unplug the connector on the low pressure switch. It is located on the pipe to the accumulator. Jumper the connector's two pins with a paper clip. Keep it from touching any ground (tape). See if the clutch will engage on the compressor.

If it does, you are low on refrigerant. They sell cans of an R-12 replacement, but I don't recall the brands. Follow the directions on the servicing hose package or read the Hayne's manual. I highly suggest using a thermometer in the duct. When it stops getting colder (~40*) stop adding refrigerant. I suck it in @ 1500+ rpm for efficiency and keep it in Norm and Med fan speed for the temp readings.