A/C cool but not cold?

[kna4977]

Factory A/C system converted to r134a didn't really cool at all when I got the vehicle.

I noticed some leakage/oil around one of the accumulator hoses. I opened up the system and found an extra O-ring in that orifice that likely wasn't removed from some time before.

I replaced all O-rings for all the hoses I disconnected. I tested the POA valve and found that it was setup for R12 pressures around 30 so I recalibrated it for R134a around 26 or 27 IIRC.

Sealed everything back up and vacuumed it down for an hour or so and let it sit. Was going to just do it overnight, but it turned into a couple of days. System held vacuum with no apparent leaks as the gauge readings didn't change.

I charged the system. Has nearly but not quite 3 - 12oz cans of r134a in it.

The air from the vents is cold when the system is first turned on, but as it continues to run, it gets less cold and the pressure on the high side seems to continue to climb it's was in the lower 200s last time I tested it, but it made me uncomfortable so I shut it down.

I can also see what looks like some liquid flowing through the sight glass on the accumulator.

I'm not sure if it's just still low on refrigerant or if there is some sort of issue like a blockage or contamination or ?

Thoughts/ideas/suggestions? I'm usually good at troubleshooting and solving A/C issues, but this one I'm not sure about.

[leddzepp]

The heater core sits right next to the evaporator core. Is coolant flow to it been shut off?

[Bob B.]

Quick check- after you have run the A/C for a while and it starts to get warm, feel the pipes into and out of the evaporator. They should both be cold, close to the same temp.. If the outlet pipes are close to the same temp., you probably have a problem with hot water flow through the heater core or the temp. damper is not closing all the way. Otherwise, you might need more air flow through the condensor if the system is fully charged. Do you have a fan shroud?

[kna4977]

I do have a fan shroud, 7 blade fan, fan clutch etc., so any issues that existed there should be resolved and appear to be. I'll check these things.

I vacuum tested all of the diaphragms and they all hold vacuum and function like they should? Water valve holds vacuum too.

Is there another simple test for the water valve maybe hose to it warm and hose out of it to heater core cool if a/c on? I will say the valve looks brand new.

Vacuum reservoir how do you know if one is bad? I hooked the vacuum pump to the input from the intake and it will take on vacuum but makes a sound and I would imagine since the ac controls are set to max cool the vacuum is bled off from those diaphragms? If I vacuum through the output of it, holds vacuum no problem.

[Richard]

Charge should be about right but may need to be adjusted, 2.8lbs is 15% under r12 charge. Main question I will ask is how does it cool at speed on highway, does it cool better? IMHO the factory condenser and mounting does not offer enough heat rejection for a 134a conversion. I have a background in hvac and a couple of conversions under my belt.

[kna4977]

Originally Posted by Richard

Charge should be about right but may need to be adjusted, 2.8lbs is 15% under r12 charge. Main question I will ask is how does it cool at speed on highway, does it cool better? IMHO the factory condenser and mounting does not offer enough heat rejection for a 134a conversion. I have a background in hvac and a couple of conversions under my belt.

I haven't really driven it on the highway. I'm basing how it's cooling off of a couple of other vehicles that I've converted or rebuilt which are ice cold and driven in the same manner around the neighborhood.

It has slightly under 3 - 12 oz cans in it, probably around 32 or so ounces which which would not be a full charge at only 2 lbs, but I stopped adding refrigerant because the high side pressures kept climbing and were concerning to me.

I also don't think I should see cloudy liquid flowing through the sight glass.

[kna4977]

I think I was just undercharged which is why the high side would keep climbing and cooling would get warmer because the system was working harder and not able to cool efficiently. I added the rest of the 3rd can and approx 1/2 of another can and it seems pretty cold. Both hoses out of the evaporator are about the same temp and sometimes get frost on them.

Still concerned about liquid flowing through the sight glass is that something to worry about or possibly normal?

[howzzzit]

Originally Posted by kna4977

I think I was just undercharged which is why the high side would keep climbing and cooling would get warmer because the system was working harder and not able to cool efficiently. I added the rest of the 3rd can and approx 1/2 of another can and it seems pretty cold. Both hoses out of the evaporator are about the same temp and sometimes get frost on them.

Still concerned about liquid flowing through the sight glass is that something to worry about or possibly normal?

I figure about 41.6 ounces, but it may want more. You should have a clear sight glass. That means the condenser is doing what it should be doing. It means solid liquid going to the txv. The txv needs liquid only to do a correct job at the evaporator. Do you think you may have let air enter the system at some point? Here's a page from the service manual.

[kna4977]

Originally Posted by howzzzit

I figure about 41.6 ounces, but it may want more. You should have a clear sight glass. That means the condenser is doing what it should be doing. It means solid liquid going to the txv. The txv needs liquid only to do a correct job at the evaporator. Do you think you may have let air enter the system at some point? Here's a page from the service manual.

I’m certainly no expert but I have done a good bit of a/c work. I suppose it could have some air in it but it would be minuscule. I’m not seeing any bubbles only liquid flowing but it isn’t clear as in you can’t see through it. Perhaps the oil that’s mixed in with it? It is cooling effectively now.

[Terry Peerson]

I went through my A/C a few years ago and discovered that the new heater control valve did not shut off flow through the heater core completely. So, I installed a manual 1/4-turn ball valve in one of the heater hoses. VOILA! the A/C was working perfectly. It was just fighting the heater core. Pretty simple and it may not be your problem. But it might be something for you to try.

[davischevy]

Originally Posted by leddzepp

The heater core sits right next to the evaporator core. Is coolant flow to it been shut off?

This is key to getting the system to work. If the valve in the heater hose on the inner fender is not closing the AC will never work. The vacuum valve sticks open or may not have vacuum to it. They are available at parts stores or you can put a manual valve inline.

I ran mine for a summer with a pair of small ViceGrips on the heater hose.

[kna4977]

I've got it cooling now. I didn't add enough refrigerant to start with. All valves and vacuum pods work as they should.

I do want to replace the schrader valve in the POA but need to know what size anyone know what I'm looking for? Currently has an R134 adapter on it so it doesn't leak but if I take that off I hear a hiss at the service port.

Also need to get some OEM looking caps for that port and the one on the muffler. Are those supposed to be brass or aluminum? Round and ribbed on the sides like on corvettes and other Frigidaire systems of the period?

[kna4977]

Anyone know what size schrader valve I need to get to replace the one in the POA service port?

What caps should I look for and get for the 2 A/C service ports to make the system look like it did when new ?