Ok I ripped my ac out 3 years ago and I am now reinstalling it. Ok...Heres my problem.

I know the ac/heater switch is vacuum controlled. Meaning that you turn it to the defrost selection and it somehow uses vacuum to open those vents correct?

Well I must have disconnected that vac line because all I have is defrost on the windshield. I need to know where the vacuum line is located so I can hook it up and have use of my vents and such.

Thanks in advance.

 

That is correct. The little doors that control the air flow, are operated by vacuum diaphragms.

There's a vacuum accumulator somewhere under the hood, I think on yoru car it'll be in the right fender behind the headlight, looks like a balck ball about 5" in diameter; vacuum goes from the manifold to the larger nipple on that, and the line that carries the vacuum to the control head goes to the smaller nipple. That line is one of those hard plastic ones, it's included in the wiring harness for the A/C (being part of that system) that comes through the firewall below the heater hoses.

 

Pull out the HVAC cluster. Inspect the line that goes into the selector switch for AC/vents/ect. If nothing is wrong there, the selector itself could be bad. If neither of those are the issue, the vacuum source under the hood is next to check. Do you hear a slight hiss all the time or anything?

 

HVAC canister has been taken out. I figure I have just disconnected that vacuum line sometime in the past 3 years when I took everything out. So it is a hardline going to that vacuum canister? I didn't take that out. It is there. I will go inspect the lines now and see what I can do from there.

 

I just ran a vacuum line to one of the previous ones above the heater core hoses. There were two....one made a hissing sound inside at the console........the other worked.

 

Some cars have a 2nd vacuum line in that harness, that's supposed to take vacuum to the heater control valve to operate it.

 

im also trying to figure out a vacuum puzzle. does it matter which one of the hardlines out of the harness go to the control valve?

 

Ok...I haven't figured that problem out yet but I have a new one.

I bought a new drier, orfice tube, and condensor. Hooked everything up. Jumped the LP switch. Compressor kicks on but I it will not take the r134a from the can. And the gauge on the line reads 80-100psi which is way to much. Maybe something is clogged?? Or maybe my compressor is bad?

When I bought the car 3 years ago the ac didn't work. And it was still full of r12. So I figured it was clogged or the compressor was toast. What do you think?

 

Gauge on the line reads 80-100 psi = the vapor pressure of Freon at summer outdoor temp

Something is blocked. Either your service line isn't opening the Schrader valve, or something isn't hooked up right, or something.

If the compressor comes on and doesn't make any odd noises, it's probably OK. Could be bad but most likely not.

As far as which line goes to the heater control valve, yes of course it matters. It's supposed to be on the low side of the vacuum switch, that lets the hot water through the heater only when it's needed. The other line is the supply to the switch; the switch send svacuum to all the little doors as they need to be operated based on the setting of the switch. It won't work right unless the 2 lines are in the right places.

 

Compressor makes some noise but doesn't sound real bad. The lines/compressor/evaporator all sat in a dusty building for a long time. I wonder if maybe something decided to live in them. I have a feeling its the evaporator....but the compressor could be bad I suppose. I know the condensor and drier are good since I just replaced them....What should I try next?

I think everything is hooked up right...I don't see how it could be wrong.

Ok just noticed something else. Sometimes I would hear the compressor get louder and the pressure would start to go down then the noise would stop and the pressure would go back up...what you think?