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a/c quit help please

Kain

Kain

3/4 ton status
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I Have put a serpentine belt system in my blazer in 2011. it has ran great only a few alternator problems but everything else works like its sapose to,until the a/c quit.

Now Im no expert but I can check to see if its getting signal and grounds so that's what i did.
And I have no signal to the compressor to engage it. If the pressure switch went out would it do this?
or do I need to check something else?

It is an 1982 body on a 77 chassis the ac stuff is 82. new condenser, compressor, evap canister ,orifus tube when it was installed. any help would be great as I cant afford the mechanic to look at it.
 
Check for power at the cycling switch on the accumulator. It may be that you have gotten a leak that released enough freon for the system to be low.
You could jump that plug and see if the clutch kicks in, but if it's low on freon, it won't cool and will be hard on the compressor.
 
well i can jump the compressor and it will run but i didnt do it long because i know it shut off for a reason and im just trying to find it. i bought on of those charging cans but when the compressor wasnt running it said 50 on the gauge when i jumped it it said 20 on the gauge. can afford to charge for a while. glad its about to get cold
 
Changing subject, but any opinions on doing a refrigerant conversion on an older K5? When I took the truck in 5 years ago, the guy acted like the old stuff is getting cheaper at this point and cools better anyway. Mine has a leak though, so I'll need to make a decision at some point. It would be nice to be able to charge it myself too.
 
134 is generally less heat efficient, so you'd want a larger condenser. There's a thread in here on the part number.
 
To address the initial problem, I think the best way to diagnose something like this is to rent an AC manifold at the local parts store and hook it up. You really only need the low side connected for this diagnosis. Then as @6872xtc said, jump the low pressure switch connector wires so the compressor turns on and then read the low pressure side of the gauge. If, you're under 20 PSI, then you are low and that's tripping the low pressure switch. Charging it should get you back in business. If you're at 0, you have a serious leak and the whole system will need to be examined. Charging it might be a pain if you don't know what kind of refrigerant is in it though. If you're already converted to R134-A, it's a breeze, if you're still using the factory R12, you need to call local AC shops to see if they still have any on hand. (you'd be surprised how many still have some).

Because these trucks are so old, many of them have had evaporators, condensers, hoses, dryers, etc. changed for aftermarket parts at some point, and to that point, its best not to charge the system based on weight, but rather charge it according to low and high side pressures that correspond to the outside temperature. When charging it, this little chart comes in handy.
m1410013_chart.jpg
 
Mastiff said:
Changing subject, but any opinions on doing a refrigerant conversion on an older K5? When I took the truck in 5 years ago, the guy acted like the old stuff is getting cheaper at this point and cools better anyway. Mine has a leak though, so I'll need to make a decision at some point. It would be nice to be able to charge it myself too.
Click to expand...

R-134A cools just fine. The reason people think it doesn't cool as well as the old stuff is because they usually convert their trucks to R-134A without changing any of the factory R12 designed components. The key is if you're doing this conversion, you should swap the OE condenser for a modern parallel flow condenser (about $100) which helps the R-134A dissipate heat more efficiently. Also, it doesn't hurt to install an electric pusher fan to the front of the condenser that switches on with the compressor to keep things cool. I did a full Classic Auto Air conversion on my factory AC truck, swapped the old four-season system for a sanden style compressor, new OE evaporator, new parallel flow condenser and pusher fan, new dryer and made all the lines in my garage. After charging the system and getting the recirculation door in the passenger kick panel to properly function, I can now get 40 degrees at the vents on High Fan in 100+ temp outside.

IMG_2135.JPG
 
1975Jimmy said:
To address the initial problem, I think the best way to diagnose something like this is to rent an AC manifold at the local parts store and hook it up. You really only need the low side connected for this diagnosis. Then as @6872xtc said, jump the low pressure switch connector wires so the compressor turns on and then read the low pressure side of the gauge. If, you're under 20 PSI, then you are low and that's tripping the low pressure switch. Charging it should get you back in business. If you're at 0, you have a serious leak and the whole system will need to be examined. Charging it might be a pain if you don't know what kind of refrigerant is in it though. If you're already converted to R134-A, it's a breeze, if you're still using the factory R12, you need to call local AC shops to see if they still have any on hand. (you'd be surprised how many still have some).

Because these trucks are so old, many of them have had evaporators, condensers, hoses, dryers, etc. changed for aftermarket parts at some point, and to that point, its best not to charge the system based on weight, but rather charge it according to low and high side pressures that correspond to the outside temperature. When charging it, this little chart comes in handy.
m1410013_chart.jpg
Click to expand...

One other point. Yes, if the low pressure switch failed, it could cause the no signal at compressor issue you noticed. Definitely check the pressures first before dropping a few bucks on a new switch though.
 
I got one at O'reilly for like $15. They're not that bad... $129 sounds like the parts guy had no f*ing clue what he was looking for.
 
Was looking online. Checking the voltage at the switch got volts going in but not out. So its got leak. But it had that green leak stuff in it and i cant find it. So off to the mechanic in october
 
If you don't see any green stuff, could be in the evaporator in the inside of the black box on cowl. It could also be a schrader valve. Could also be on the back side of the condenser behind the radiator.
 
the cap you pull off to check for pressure had the green stuff on it. is there a way to change the shradder valve without replacing the hole thing?
 
cant post pics till next month spent to much on front end rebuild, i can message em maybe
 
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