This sure seems like a stupid question, but here goes.

I bought a can of 134A freon with the leak stop in it to see if that's all I need to get back to optimum.

My AC still blows, sometimes cool, sometimes not quite as cool, and every once in a while with an odor. One time it blew some visible smoke of some kind, but just that once.

It still works well enough to call it AC, so there's that.

So the can, and common sense, says to use the low-pressure Schrader valve, which should be between the compressor and the evaporator/firewall.

I can only find two Schraders, the high-pressure one between the compressor and the condenser, and another between the condenser and the firewall. This one I would call intermediate, but still doesn't seem like the one I should be using.

The suction line comes from the firewall, into the accumulator/receiver, then on to the back of the compressor. The only other thing on the top of the accumulator/receiver is what I would assume is the low-pressure cut-off switch.

I do commercial and residential AC service, so I know the basics of the process, but I have no experience with automotive systems, layout, or R134A.

 

If it's the smaller diameter schrader fitting then it's low pressure. High pressure is always the larger diameter connector.

 

On my 95 it is forward right side of compartment.Forward of the battery next to the radiator.

 

Low pressure is closer to the firewall...high pressure is near the condensor up front.

If it's a store-bought a/c tune-up-in-a-can it should only fit that valve. Sometimes they come with a gauge on it that tells you when the pressure is in the "good" range.

 

So then unless I'm supposed to use the one between the condenser at the evaporator (which on a residential or commercial system is still high), then I don't have one, which makes no sense.

I can see no valve between the firewall and the compressor.

I'm going to go outside and look AGAIN.

Is this valve between condenser and evaporator considered low on cars?

 

Can you be more specific? I can't see any valves near the firewall.

 

Again, please be specific. What are you calling a low-pressure valve? The one on my truck in that location is on the tube between the condenser and the evaporator, NOT between the evaporator and the compressor.

 

I was finally able to confirm that this is the right answer. Apparently, cars can have the "low" be in between the condenser and evaporator, even though in the rest of the world this would still be the "high" until it leaves the evaporator on the way to the compressor. WEIRD.

The can's instructions said after evaporator, too, which is why this was confusing.

Anyway, it was in the green before I started, but in the lower half, and not matching up with what the dial would say for my ambient. I added enough to bring it to the top of the green.

I keep a thermometer in my vents, so I've got a good baseline of performance the past several weeks. I'll see what difference it makes starting tomorrow.

THANKS GUYS!

 

I guess I was wrong....on my 98 it is different then the earlier trucks. I know for a fact the high pressure port is right in front of the battery and the low pressure port is behind the air filter box. I think the reason is in the later models the orifice tube is inside of the liquid line, on earlier trucks (like your 96) its in the condensor...learn something new every day!

 

Gorms right. Thats where they are on my 96. You should really use a can on 134a that have a gauge on it and also find out what the pressure should be at the temp your recharging at.

Bob