I recently purchased my 79 vette. I live in FL and my ac is not blowing cold. It does blow sort of cool.

I've had the controls checked and everything is working as it should. I had the compressor replaced and the unit recharged. It had already been converted to R-134.

In reading the other post, could the orifice tube be the problem? The accumulator also was not replaced with the compressor?

Help, it's hot down here.

 

Hey there 79,
I have been through this and I took shortcuts the first time and ended up replacing the entire system. When you replace the compressor - it is almost always recommended to replace the orifice tube and the accumulator along with the compressor... otherwise you could potentially ruin your new compressor. I sure hope that isn't the case for you. But - if you just had the compressor replaced and recharged.... and it was blowing cold for a while - then you most likely either have a leak in the system - or the compressor could have been damaged by a contaminated accumulator / orifice tube. I'd get it to an A/C shop pretty quickly to have them check for leaks first... if they find one - have it repaired and then recharged. Hopefully that will fix it... if not - you may end up having to replace the compressor and the other two parts again.

Good Luck... Hope it's something simple.

 

Thanks for the heads up. After reading the post today I will get these replaced this weekend.

 

Something to keep in mind... Have it checked first. The major expense of replacing the Accumulator is the Labor - it's a pain to get to. If you have already contaminated your Compressor - it won't do you any good to replace the Accumulator and Orifice tube now - Until you replace the compressor again

I do hope that's not the case for you... Just wanted to give you the heads up.

Here's the sequence of events with the System on my 78 Coupe.
1. A/C system worked but just barely - so I had the Compressor replaced and The System Recharged. I was told at the time that there was a 50/50 chance this would be ok... I was willing to take the chance to save the Expense. I Purchased A Remanufactured Compressor (Non AC Delco Brand). The system blew cold for about a month then went down hill
2. Had the system checked because it stopped blowing cold... there were leaks from the compressor... There was suspected damage and it was recommended to replace it. It was also suspected that the cause was the fact that I failed to replace my Accumulator and Orifice Tube at the same time

To Date I had only spent about $350.00 parts and Labor

3. Had the entire System Replaced with all AC Delco Parts - Compressor, Accumulator, Orifice Tube, Header Assembly, and all original R12 Freon, Oil, Orings, etc... Cost - $1600 parts and labor. Everything is running beautifully to this day. I should have done it right the first time. I won't take short-Cuts again... I basically threw away $350.00 not to mention the time I spent ...

I can't say this is the case for you but it was my experience and I thought it worth sharing.

Good Luck

Cheers ~ Joe

 

So you went back to the R-12 set up?

I have looked at the accumulator and it looks like it will be tough to get to.

How can you tell if the compressor has been contaminated?

 

Your not blowing cold can stem from a number of sources or combinations and not necessarily the a/c part itself.

Bypass your heater core to test that hot air isn't mixed. The foam at the hose connections still there. You don't need heat here anyway.
Make sure your recirculate system works, the flappers in the correct positions and sealing tight.
Your firewall to fender bond at the pass fender is not cracked and leaking hot engine air.
Your underdash ducts are still joined well enough to direct air to the vents.
Degrease and wash your condenser and radiator.
Make sure your engine fan is working properly.

For the a/c part,
Measure the temp of the 2 evaporator lines, the out line should be as close to 32 as possible.
Whoever changed the compressor should have changed the OT and the accumulator.
Both should be changed anytime the system is emptied. If they didn't, find another a/c place.
Any damage is already done so, put the acummulator and oriface tube in and charge to get the evaporator temps as low as possible and see what happens.

If not, the next steps will get lengthy, but good news is on the horizon. it should drop down to the high 80's by Sunday.

 

I just went through replacing my compressor, oriface tube, accumulator/dryer, change over to R134a, evacuate and charge in my '79. I did it myself. Getting the accumulator out of the car is a PITA but not as hard as you might think if you take it out the bottom through the access panel that can be removed for this purpose.

All the advice is above is good stuff. Before you spend a lot more time and money first check the hot water shut off valve to see if it is functioning. The plastic vacuum hose that connects to it gets brittle, can crack, leak vacuum and prevent the valve from shutting off the flow of hot water to the heater core. It takes vacuum to shut off the valve and no/low vacuum to allow hot water to flow.

My hose was cracked and hardly noticeable but I trimmed it back and reconnected the hose. There is a lot of heat competing with the A/C system from the vents and the temp of the box under the dash if the valve is not shut off. Just lay your hand on the heater core under the dash and see if it is not hot when the HVAC is in A/C mode. If it is still hot as it would be in heater mode, then your shut off valve is not functioning.

 

The only control positions where the hot water valve is supposed to shut off are the OFF position and the MAX (interior air recirculation) setting; all other settings need that valve ON so your temp control can regulate temperature level of the system air. So put your control on MAX to see if it blows cold or not. Also, check to make sure that your compressor is even coming ON. The pull-in coil/switch may be bad, of the compressor fuse/circuit breaker blown; the blower will still work but that doesn't mean the compressor is ON or that it is even getting power.

 

I think 7T1Vette is right about the max A/C position. I put a vacuum guage on the plastic line that I could see from inside the car and moved the lever between off and the first A/C position which is max. I had little to no vacuum in that first A/C position (max). After trimming down the hose to remove the cracked portion I had 10 in Hg which was enough to close the valve.

 

Some factory systems were converted from R-12 to R-134a by only 1 mech. change- reducing the orifice tube!
Some A/C shops are changing the GM orifice tube to a smaller Ford tube which has 2 O-Rings to seal better.

To improve A/C perf., changing the GM white orifice tube .072 to the Ford red .062 should be best orifice tube.

 

Thanks for the tips. I did have a problem with a cracked hose to the hot water shut off. I put in a new hose. I think I'm going for the oriface tube, accumulator/dryer fix next.

 

Thanks for the tip. That sounds like a good idea.

 

On a 79 at least, the heater hose cutoff valve is operated by the
COLD................................HOT control lever.
The lever must be on the cold setting, all the way to the left. If it's even a 1/4" off the cold, the vacuum switch behind the glove box won't activate the vacuum shutoff on the heater hose.

After 25 years of no cold AC on my black79(never really used it anyway!), I finally looked into it this past spring. As the Vette would first start and warm up, I'd have nice cold air, but as it got to operating temp I'd loose the cold.
Upon removing the glovebox and checking the vacuum switch mounted atop the heater box, I could see that the mechanical cable and lever from the temp control did not depress the plunger on the vac switch.
I found that one of those little plastic tips you'd see on wire closet shelving fit perfectly over the plunger on the vac switch.
Problem solved, ice cold air now

 

KapsSA is absolutely correct. I'm getting old. It was the temp lever that I moved.

 

come to mn to drive and i bet it will blow cold air 38 degres today lol