AC lines too hot

[fsjeep]

I got a 94 Chevy ext cab 350 last wk and going through fine tuning it. The system has been converted to r-134a (stickers on compressor and dryer, and correct connections on hoses, not retrofitted) The ac didn't work, leaking. So I fixed the leak, checked orifice (clean), pulled a vacuum and it held for about 30 min. Using a chart I found on here at 80° I charged it to 200psi (175-210 suggested) high and it only got to about 35 psi low (40-45 psi suggested). My thermometer in the vent showed it blowing 60°. Everything is working, awesome. When I pulled my guages off the high side the line just about burned my fingers. Then i checked the low side and it was only cool, not freezing. I remember seeing somewhere that a hot high side is a symptom for... I dont remember what. Also once the high side pressure gets over 150-ish psi the compressor starts to quietly growl.

[ChevLoRay]

to the forum!!

This is not the right weather to have AC troubles. Because I don't know AC systems and because there are people on here who do understand them, I'm just gonna have to hope they'll jump in here and offer some knowledge.

So, give us a little time and the right info should be seen on this very spot!!

[bwood]

The high side will be hot, hot enough to burn in some situations, thats normal. This is common of AC systems, thats why there is a condenser. The compressor in compressing refrigerant from a gas form to liquid form and this creates heat and pressure. The condeser cools the liquid down to a point that when it sprays through the oriface, it will easily turn back into a gas. As far your discharge air temp, you need to verify that the blend door is closed and you're not getting some hot air from the heater core. Your pressures are not that far off. Your chart matches mine (Interdynamics Chart?) Do you know how much refrig you put in / original system charge?

[ChevyTech]

Like bwood asked, I want to know how much refrigerant you put in it.

When I have a system empty I charge it up by installing the capacity listed and not by the pressure reached.

[bwood]

Ok, I just noticed your post says your truck is a 94, it should have been R-134a from the factory. How much refrig did you put in? The two 94's in my camp were R-134a originally and so was my aunt's 94.

[fsjeep]

I'll try to catch everyone's questions here:
bwood-I'll check the blend door, I found the chart here & don't know the original origins, less than 2 12 oz cans of freon (don't have a way to measure quantity), Guy at Oreilly told me they didn't get 134 until 95 but looking up the hose he sold me that is for a 94 has connections for 134... so it wasn't converted!
ChevyTech-like I said less than 2 12 oz cans

I'm no ac expert but I certain I have read that ac systems only reduce the air 20° from the ambient temp. So I thought dropping from 80° to 60° was good, should I be getting colder? Also when testing I didn't have the recirculation turned on.
Another major concern of mine is being a serpentine system, if the compressor locks up the belt burns up. I'd rather drive in the heat than walk in the heat. Is it normal for the compressor to growl slightly? What are the odds of it locking up? Or would only the clutch locking up cause this? (It's amazing what you can think of when writing something out!)

Thanks for all the help, this forum is a great wealth of information!

[ChevyTech]

You're welcome,

The amount of humidity has a big affect on the out air temp. The ambient temp and humidity are used to look up and acceptable outlet air temp on a chart.

Performance tests are done with the AC in the MAX/ recirc position, fan on high, with the engine @ 2000RPM, and the hood closed(yes it can make a difference).

Be careful what chart or spec you use.

I am fairly sure that 1993 was the last year R-12 was used in the C/K trucks.

The compressor can be seized, but if the clutch is not engaged the belt and pulley will turn just fine.

[bwood]

(2) 12 oz cans is only 1 lb 8 oz of refrig, I'm thinking it should be around the 2 lb range (1/2 can), it may say on top of the accumulator on the passenger side of the firewall. You generally don't get all of the refrig out of the cans, I usually figure about 1/2 oz left in the can when I'm done. A refrigerant based cooling system is usually good for at least a 20 degree difference (delta T) Minimum. Bringing in 80 and putting out 60, on the way home today, my 98 was bringing 100 and putting out 60, then in recirc it gets down to 40. Have you put it in recirc/Max, it should make its way down to the low 40's. Sitting still also is not a great way to test as you start to recirculate hot engine air back across the condenser lowering its effeciency. The growl is the unit loaded up, if it wasn't making a little noise (should sound like a "clatter" noise), I would think low charge.

Where's Ama, Tx, Amarillo?

[fsjeep]

Originally Posted by ChevyTech

You're welcome,

The amount of humidity has a big affect on the out air temp. The ambient temp and humidity are used to look up and acceptable outlet air temp on a chart.

Performance tests are done with the AC in the MAX/ recirc position, fan on high, with the engine @ 2000RPM, and the hood closed(yes it can make a difference).

Be careful what chart or spec you use.

I am fairly sure that 1993 was the last year R-12 was used in the C/K trucks.

The compressor can be seized, but if the clutch is not engaged the belt and pulley will turn just fine.

What chart is best to use, I don't have anything factoring in humidity. I'll check out the AC again today as I had the hood open and whatever the truck idled at. Awesome, being a black truck I'll just run the AC!

[fsjeep]

Originally Posted by bwood

(2) 12 oz cans is only 1 lb 8 oz of refrig, I'm thinking it should be around the 2 lb range (1/2 can), it may say on top of the accumulator on the passenger side of the firewall. You generally don't get all of the refrig out of the cans, I usually figure about 1/2 oz left in the can when I'm done. A refrigerant based cooling system is usually good for at least a 20 degree difference (delta T) Minimum. Bringing in 80 and putting out 60, on the way home today, my 98 was bringing 100 and putting out 60, then in recirc it gets down to 40. Have you put it in recirc/Max, it should make its way down to the low 40's. Sitting still also is not a great way to test as you start to recirculate hot engine air back across the condenser lowering its effeciency. The growl is the unit loaded up, if it wasn't making a little noise (should sound like a "clatter" noise), I would think low charge.

Where's Ama, Tx, Amarillo?

I'll mess with it more this afternoon. I stopped at 200 psi high side knowing overcharging the system is a no-no. But like I said I'm not factoring in humidity and it's been oddly humid here lately (usually nonexistent).
Yes sir big ol' Amarillo

[ChevLoRay]

If the smell from the stockyards was humidity, you guys would never get dried out.

[ChevyTech]

Originally Posted by fsjeep

What chart is best to use, I don't have anything factoring in humidity. I'll check out the AC again today as I had the hood open and whatever the truck idled at. Awesome, being a black truck I'll just run the AC!

I always just copied the chart out of the GM service manual to keep it handy for quick reference. I have one I made up for R-12 refrigerant on my computer but don't have one for 134A to share with you.