First of all, I'm pretty sure this needs to go in this forum. The A/C on LT1s is different from LS1s so I'd expect different advice.

Anyway...

To start, a year ago my compressor died. My A/C before this had always worked just fine. I bought a brand new A/C Delco Delphi compressor off of eBay and installed it myself. I didn't charge it right away, but about a month or so later I got around to replacing the accumulator and charging it. It worked, but not so well. It was just not very cool at all during the day. I figured I just had moisture in the system.

Fast forward almost a year. I got sick of it not working well. I asked around and people told me to get a new orifice tube (which I later discovered is not even present on the LT1 system) and vacuum it out and charge it. So I got a vacuum pump and manifold guages from a friend and vacuumed it out for 15-20 minutes at 29" Hg. Then, I hit it with a PAG oil charge, and then it took about 3 11oz cans of R134a coolant. I filled it to 42psi or so, at 80 deg ambient outside.

And.... guess what. Didn't help anything at all. Not one bit. It still blows.

Whats wrong guys? Help me out here!

 

Your correct, you don't have an orifice tube BUT you do have a thermal expansion valve (TXV). If your compressor got wiped out, more than likely it put metal in the system. In that case you will need a new TXV and you WILL have to flush the system. At this point you need a new dryer also. Flushing is best left to the AC experts. When you recharge it, be sure to put dye in it so if you have a leak, you can find it easily. BTW, when you vacuum it down, leave the vacuum on it longer than 20 minutes. Be sure to cut the vacuum off and leave it connected for a while to be sure the vacuum holds also.

 

slopoks on the right track. first I need some questions answered.


what happened to the old compressor? did it leak? did it lock up? was the system flushed after that at all? when the new compressor was put on did you add oil to the compressor? how much? did you prime the compressor after you added the oil?

 

Yes added oil to the compressor, I forget how much, it was a few ounces as called for by the instructions. I didn't prime it, no.

The old compressor lost a seal I think. It never locked up, it spun pretty freely.

System was never flushed.

Also the system doesn't seem to be leaking anywhere.

 

you could have added too much oil.. 8 ounces is good. you should usualy flush the condensor anyway just to be safe. and since there is no orifice tube generaly anytime you make a repair to the system teh expantion valve should be replaced. there could be a tiny bit of debris in the valve. without seing your pressures I can;t tell you much. are the fans coming on with the AC on?

I would take it down, replace the h valve. and the drier just to be safe, put a vacuum on it and recharge it bac to the manufatires specs for weight.

 

You may be right about the amount of refridgerant it took. I have the full manifold guage set but I never checked the high side... I bet its way high, thats why it took so much to get the low side pressures up....

How much is involved in replacing that expansion valve? I pulled the whole thing off (two inverse hex screws) the firewall and inspected it but couldn't see anything (at this point not realizing that there was no orifice tube whatsoever) so I put it back on. I assume I would need to somehow unscrew the lines from the front of this valve block... they look like they're probably on there pretty good, I bet they're a PITA to get off.

Also, should I replace my receiver/drier even though I vacuum the system?

Are there any trash screens (where there could be debris) in the system that I may have missed when I replaced the compressor?

What is involved in flushing the system?

 

By the way the fans are coming on.

 

Went and got a GOOD manifold guage set today (Harbor Freight one sucks) and checked out the low side pressure again. I bled it down to about 35psi from 45psi. I then checked the high side. The high side is now around 165psi, with an ambient outside temp of maybe 75 degrees. It made a noticeable difference, A/C blows colder, but still not as cold as I feel it should. If it were during the day, I'd call it fixed, but since it was at night I'm sure it wont be as cold in the day.

 

Did you compare the size of the pullies on the compressors?

there is a small and large, the wrong size and it won't work quite right

 

yeah. thats not gonna do great when you get to higher temps. by looking at teh pressures I would say that the h valve is alright but for a sanity fix you might wanna replace that. was the drier ever setting open or in the car while the lines were open for more then a min or 2? if it was then replace it again anyway. it takes no time at all for the drier to soak up teh moisture in the air when it's open.

I think a drier, h valve, vac pull and the proper charge by weight would do the trick for you. check on the sticker and tell me how many pounds of freon the car calls for and I can tell you how to figure the weight charge.


as for changing the valve I would have to look at it but usualy if you hold the valve with pliers you can break the lines look from it.

 

I think I will replace the valve anyway like you say. Yes the drier was sitting open for a while when we were tooling around with the valve before. Its also an aftermarket one (black) and IMO a piece of junk from the looks of it. I'm just going to order a new AC Delco drier. Do I need to oil that before install? Which viscosity oil do I want to use?

Also my new manifold guage set says I need to vacuum the system on the high AND low sides (previously only did low). Does that sound right? If I vacuum it for like 20 minutes would that be enough?

 

By the way the compressor is absolutely identical to the one I replaced.

 

OK

and vac both hi and low, 20 min should be plenty

 

Since you went ahead and got a manifold gauge set, you might as well spring another $4 for a thermometer. Most cheapo auto stores sell the type that clips to a vent. Then you can tell exactly how cold the air out of the vents is. I've always left it in for a week or so in each of my cars I've done AC work on to keep an eye on performance until I'm satisfied that there aren't additional leaks.

I had a leak in my '97 Formy three weeks ago. It turned out to be the schraeder valve on the low pressure side. When I charged it to 42psi low side (I forget the high side pressure) in 89°F ambient (daytime) I was getting 58°F air out of the vents on max/high after letting it run for 15 minutes or so. This was sitting in blazing sunlight with the T-top shades off.

The car now blows 52°F to 58°F depending on how hot and sunny it is out. I haven't measured wet bulb, but we have serious humidity down here. You might get colder air in a dryer climate at the same dry bulb temps.

Hope that gives you something to compare to. Good luck!

 

yes get a new drier. most are not black. yours is teh first non ford and import that I have heard of being black. do not add oil to it but for refference on a 134a system use PAG 150.


you do not need to vac the high and low side. you can but it's not gona change anything. vacuum the low side and then once you do that for a while and you start to charge stick the can on and peirce it and open it up. then losen the middle fill hose at the manifold block untill freon comes out (just a minor step to getting a little air out of the hos eto make sure you get a proper charge.

Still tell me what the sticker says for how many pounds the charge is and I will tell you how many 12 ounce cans to use.


Thermos in the vents just play with your mind. they do not help you at all. I can't even count how many people come in saying that they need freon just cause the thermo reads higher then it did in teh morning or days ago when it was cooler out. ambiant temp has direct influence on both pressure and the ooling of the system.