Air Conditioning Issue.

[Averix]

Ok... So I sifted thru about 4 pages of a/c threads on this site and didn't see anything that matched what mine is doing. I have a 2000 GTP with dual climate control, two little sliders that go from red to blue. If I have the dial set to max a/c, the a/c button lights up, and I get air movement. If I slide the sliders all the way up, hot hot air comes out, slide it down, cooler air comes out, can hear something moving, assuming blend door, but not 100%. Air only feels cool as in forced air cool, not conditioned air cool.

The odd thing is the fact that the a/c clutch is engaging, a/c fan is kicking in, and the system pressures are all perfect, drops right to about ~35 psi on the low side while running. Everything seems to be working, but no -cold- air on either passenger or drivers side. Never had water on the floorboards, I can physically watch the pressures drop from equalized when the system is off, to right where its supposed to be while running. Any help with this would be seriously appreciated!!!

[dsmuts]

Is it cool on both sides or is one cooler than the other? Could be a blend door issue.

[Averix]

Same temp on both sides, I'm ready to start kicking things and see if that helps...

[Averix]

Is there any easy way to check the blend door? Access port? Magic words? Something?

[mkyota1]

Is the line going to the evaporator cold? If it is really cold you know the problem lies somewhere in the dash. Do you know what your high side pressures are?

[Averix]

I wouldn't say cold, it's cool. Unfortunately I only have a fitting to adapt to the low side for my gauges. Think it might just be a freon level issue and heat just happened to be just right to push the pressures into the right level for what I should see on the low side?

[dsmuts]

How fast does the compressor clink off and on?

[Rico]

Don't forget that suction pressure may vary with engine bay temperature. If the motor and engine bay temperature is hot then the suction pressure may be as high as 40-50 psi. This is assuming that the system is R134a.

When people say "evaporator" I'm assuming they mean "accumulator", the big silver canister? The evaporator is up in the firewall.

If the accumulator isn't getting cold then the system is either low on R134a or the compressor's efficiency has dropped off. The high side pressure should be roughly 5*low side pressure. If the high side pressure is >175psi when the low side is 35 psi then this may be an indication that it's just low on R134a. Conversely, much lower than 175psi then compressor may be damaged.

[Averix]

So basically I'm going to have to track down an adaptor for my high side. And yea, I was checking the lines by the firewall when they asked me to check the evaporator, was the only place I could access it lol. Ill check the accumulator today after work and see if I can scrounge up a fitting for the system. Also since I don't see any tx valve on these things, does it use an orifice tube? If so, would they get plugged and cause an issue like this? Either way I'll post back with my results once I get a gauge hooked up to the high side.

[Rico]

So basically I'm going to have to track down an adaptor for my high side. And yea, I was checking the lines by the firewall when they asked me to check the evaporator, was the only place I could access it lol. Ill check the accumulator today after work and see if I can scrounge up a fitting for the system. Also since I don't see any tx valve on these things, does it use an orifice tube? If so, would they get plugged and cause an issue like this? Either way I'll post back with my results once I get a gauge hooked up to the high side.

I think thermal expansion valves are a thing of the past for the automotive industry. The accumulators are strange animals. They work in conjuction with the orifice tube as expansion and drier.

I guess they can get clogged but all the oil will get pushed into the evaporator and probably trash the compressor. The high side pressure would go through the roof. The low side may go to 5 or 10 psi.

Maybe someone with a little more expertise will comment. I'm just a weekend warrior. Every car I have owned has had AC problems.

[Averix]

Lol, I'm more at home under the hood of my '70 bonneville than I am under the newer style cars. Everything is different, including the air conditioning. But, with what your saying, I should be able to rule out orifice tube due to the low pressure being in the 30's. So more than likely a high side comparison is going to show me I need more 134a. Which is going to confuse me even more, as there is dye in my system, and I did look it all over.... without seeing any dye.... so where the hell did it go.... Sometimes I hate refusing to let other people work on my car!

[dsmuts]

Do you have a black light and the special glasses to see the dye? When my ac was messed up i couldn't see any dye and it ended up being the compressor was bad and leaking it out and i couldn't even see it.

[Rico]

Lol, I'm more at home under the hood of my '70 bonneville than I am under the newer style cars. Everything is different, including the air conditioning. But, with what your saying, I should be able to rule out orifice tube due to the low pressure being in the 30's. So more than likely a high side comparison is going to show me I need more 134a. Which is going to confuse me even more, as there is dye in my system, and I did look it all over.... without seeing any dye.... so where the hell did it go.... Sometimes I hate refusing to let other people work on my car!

Why are you assuming that is leaked out? I don't see results for a high side comparison yet.
There may not be a leak, just a bad compressor.

"Sometimes I hate refusing to let other people work on my car!"
Yea, that's one of my imperfections also. It gets me into a lot of trouble. LOL

[Averix]

@ Dsmuts: Yes, I've got pretty yellow glasses and the flashlight to see it. I've had situations where even they didn't help, one was a leak on an evap coil tube, wasn't until i sprayed some soap on the damn thing did I see the tiny little bubbles.

@ Rico: Because I want it to be leaking instead of a bad compressor lol. I couldn't find an adaptor and none of the other guys had one, so shopping time tomorrow I guess!

[Averix]

Ok, as for an update on the situation. Accumulator does feel 'cool', not 'omg I'm getting frostbite' or anything. Pressures with system off is about ~90psig, and with system running its about ~170psig high side, ~35psig low side. Temperatures between drivers side, middle and passengers seem comparable from startup, straight thru shutdown after leaving it run for about 20 min. I'm starting to suspect low levels, shouldn't there be over 200psi of pressure on the high side?

[Rico]

5 to 5 1/2 * low side.

175 to 193.

I agree with your suspicion; just low on R134a. The compressor may be losing some efficiency though. Try to get the low side up to 40 psi and see what happens. Compressor efficiency is not directly proportional to pressure. If you fill the system it might start working like gang-buster.

How quickly does system pressure equalize after shut down? This will tell you if the accumulator needs to be replaced.

[Averix]

System pressure doesn't take that long at all to equalize. Gonna track down some r134a and add some this week, should also see if there's oil in the system too. You guys have been a big help with this! Wanna tackle the climate control system on my '70 bonne next?