72 c10 Factory Air Conditioning Advice Needed?? Not blowing COLD!

[dlct3]

Ok, so here's the deal. I'm trying to get the factory ac working again.
Here's what I've been through over the past couple weeks and info regarding system. I've replaced the compressor with a remanufactured one, new a/c expansion valve, new R134 updated POA valve with clutch switch kit, 134 fittings, new control cables, all flaps working properly, new vacuum lines, & the condenser is flowing. Also, when I replaced the compressor today I looked to see if the bag had busted in the filters looking for little black pieces and found nothing which would make me think the condenser is fine. Just cant get it cold. vents say about 78-80degress maybe slightly colder while driving, but not under 70ish. Also, tried different lb amounts ranging from 2 lbs to 3 3/4lbs as recommended from factory (which makes the compressor knock slightly and sweat on the outside of the compressor itself)
Hope al this helps. Someone cure my woes!!

Thanks

[newstang79]

Make sure your heater hose valve to stop hot water to heater core is stopping flow to core. If it is allowing water to circulate (if they both are hot) you will never get cold air no matter what you do. If your large line (suction) is sweating back to compressor you have a full charge.

[Bigdav160]

Out of curiosity, what type of oil did you use? You didn't replace the drier?

I'm not saying that is the problem. The OE condenser is going to be too small for R134a

What are the pressures? That's important.

[dlct3]

[QUOTE=Bigdav160;6729854]Out of curiosity, what type of oil did you use? You didn't replace the drier?

I'm not saying that is the problem. The OE condenser is going to be too small for R134a

What are the pressures? That's

I'm not sure on these answers exactly as I had a mechanic completing most of these. I know he used an ac oil that was died green when he filled the compressor. I'll pass the info on to him about the co sensor and try to get answer on what the pressures were. Seems like hee ruined low side was around 40 but don't quote me for sure

[dlct3]

Originally Posted by newstang79

Make sure your heater hose valve to stop hot water to heater core is stopping flow to core. If it is allowing water to circulate (if they both are hot) you will never get cold air no matter what you do. If your large line (suction) is sweating back to compressor you have a full charge.

Ok. Can you lead me in the right direction as to where this is located and best way to check and test it? I do believe it was sweating. I'll verify. Thanks for the help guys. Really appreciate it. The next step he was going to take was replacing the compressor with a 10 valve

[GSFMECH]

You mentioned you used the POA valve w/ switch? If this is the one from Old Air products it has an adjustable pressure switch, you are going to have to adjust it so the low side pulls down to about 25- 26 psi or so. Pull the plug off and look in the end and you'll see a screw, this is the adjuster. Go only a little at a time. I never had luck with those, I personally like keeping the original POA valve and adjusting it down so it maintains 26 psi or so in the evaporator. It will take about 56 oz or so of 134A to fill it properly. I've been fighting these factory units for the last 25-30 years.

[dlct3]

Ok. More great tips. I'll pass these along. Here is what I have from classic parts
(1967-72) POA Valve Update Kit - R134
Item Number: 68-969B

Is this one adjustable as well you think?

[Bigdav160]

The switch is adjustable. There should be a screw head between the electrical blades.

[GSFMECH]

Most likely, if you pull the electric plug off, look between the prongs and there should be a screw, if you go too far with it it'll mess the switch up so take it easy. The valve newstang was talking about is in the heater hose and should be mounted to the inner fender, if you have leaking flaps it will affect it. Big thing is to get the charge right and get the pressure setting on the switch right and it should work, the problem I had was with the setup you have was it cycled too quickly, at first it would work good for a while and then freeze up. I think it may be because of this system having an expansion valve instead of a fixed orifice. I gave up and went with the original POA valve but you need to test them and readjust them for 134A.

[dlct3]

Ok, So heres a quick update. Any advice now?

The POA valve set screw should be working fine and adjuted correctly according to mechanic. He said it was going down to 25-26 on the low side. Also, I took a couple pair of flat vise grips and pinched the heater core lines off to check the heater valve and the air conditioner on high went from 85 degrees driving down the road to about 70 degrees driving at the center vent. so a decent swing, but still not cold. Mechanics going to drain the refigerant and refil as he said he had it colder when he had less lbs of r134. about 2.5 to 3 cans instead of the almost 5 cans factory recomends (12oz cans) The POA valve itself is cool and dripping, but not cold like it should be.

Anyone care to advise? Thanks again

[JointTech]

what temp should a factory AC be blowing? I read a post yesterday and it seemed like the guy was really stoked it was blowing at 65. From what I remember it should be way colder than that at the vent for modern cars.

[dlct3]

I've read and been told around 38-44 at the vent which is what others are seeing on same systems

[JointTech]

ok thats what I thought. Now to find that other thread and let that guy know his AC isnt cold maybe hes somewhere cold so it doesnt matter.

[leddzepp]

Your factory AC system will never get as cold as it should with R-134, unless you get a modern condensor designed for it. I played games with that crap on several trucks. I went back to R-12 and will never use R-134 again on a factory system. My truck stays ice cold sitting in dead stop traffic in 110 degree heat with no problems now.

[dlct3]

Originally Posted by leddzepp

Your factory AC system will never get as cold as it should with R-134, unless you get a modern condensor designed for it. I played games with that crap on several trucks. I went back to R-12 and will never use R-134 again on a factory system. My truck stays ice cold sitting in dead stop traffic in 110 degree heat with no problems now.

I think that may be my next step but I know of other systems on r-134 that are low 40's so what I have should certainly be a whole lot better. unfortunately, now i have a poa valve for r134 and if r12 doesnt make a difference I've wasted that $$ as well which probably isnt very cheap is it?

[1972SUPERSB]

I just rebuilt my factory AC and replaced just about everything in it. Only thing I kept was the evaporator and I just flushed it out. It blows 45 degrees out of the vents. If you do it right R134 is just fine

[dlct3]

Originally Posted by 1972SUPERSB

I just rebuilt my factory AC and replaced just about everything in it. Only thing I kept was the evaporator and I just flushed it out. It blows 45 degrees out of the vents. If you do it right R134 is just fine

Thansk for sharing. can you tell me what you replaced besides the compressor, poa valve, and evaporator? Also, what dryer did you use?

[joey8383]

The compressor sweating tells me the suction line is pretty cold and well below the dew point (and the evaporator is cold too). Really need to get the pressure readings, outdoor temp, and a cab temp. Roughly, your condensing temp (high side converted to temp) should be ABOUT 30 degrees higher than the outdoor temp. If it still has the small R12 condenser on it, you may see higher head pressure. The only way to get the charge right is to vacuum it and weigh it in. I suspect the heater valve is open and your heater core is flowing hot water through it. Are both heater core lines hot? Grab some crimp pliers and pinch off the heater hose and see what happens. But really need more info/readings. Good luck!

[1972SUPERSB]

Originally Posted by dlct3

Thansk for sharing. can you tell me what you replaced besides the compressor, poa valve, and evaporator? Also, what dryer did you use?

I replaced the compressor with the one from old air products, all new hoses, new AC delco drier, poa valve, new condenser, AC delco expansion valve,