I've had numerous problems with my A/C

It started a few years ago. I was driving on a trip and the A/C went off!
Fan worked but no cold air.

After some time it came back on then went off again.
The A/C button was flashing.

I discovered that when it went out if I disconnected the negative cable
on the battery it would work again until I turned the car off.

I changed the high pressure switch and still had the same problem.

I then had a shop look at it and was told I needed more cooling fans
to the condenser because it was too hot and the pressure would build.

The shop said they would put a little more freon in but they didn't like doing it because of the pressure.

Well,guess what? It worked fine for about 4 months.
(I don't drive it much)

Now it stopped working again but the A/C is light is solid,like it should be,but no cold air.

Negative cable didn't work.

I tried jumping the high pressure switch but it didn't help.
Fuses check out good!

The compressor just won't start.

Any ideas?
Thanks
Herb

 

Low pressure, most likely. Pull the HVAC fuse, put it back in (with the key on) try it again. Mine was trying to pull that on me recently when I was trying to charge it after having the system taken apart. The computer is pretty good at detecting when there's a problem, and if there is, (or it thinks there is) it will NOT allow the compressor to kick in. If you don't drive it much, it's likely a bit low in freon.

 

Thanks for the quick reply but I thought I read somewhere that when it's low on freon
that the A/C control light flashes?

Mine is on steady?

 

If it is a C68 electronic HVAC check out this post

http://forums.corvetteforum.com/1570426699-post29.html

and see if there are any codes.

 

Do you have a c68 system? If you do you can pull a code by pushing the fan up and down button the same time for about 5 secounds. I think a 09 code will be low freon. I had the same problem in my 93 i added a can of sealer and its been good for the past 3 months. Your manual should show what the other codes mean.I think there are a total od 10? Im hard at work so i dont have access to book. Search the forum you will see alot of possible ideas and good luck. Dave

 

Seems like it should. When I was charging it, and the A/C compressor quit kicking in, the A/C light didn't start flashing right away. Doesn't really make sense to me either, but, yes, a check of the codes will steer you in the right direction, but a check of the system pressure with a gauge will tell you for absolute certain.

A bad switch will throw a code, but a pressure check will tell you if you have a bad switch or not.

 

Yeah to pull the code from the a/c i think the light has to be blinking. I know i cleared it by pulling the negative cable.

 

Sure hope you didn't jump the High Pressure Switch (actually a thermistor like sensing device) as that would tell the PCM it's about to explode and it would shut it off.

These Years are pretty good at diagnosing whatever the problem is leading me to believe that the Processor senses an ok condition and that it isn't working because something is not supplying power to the compressor clutch. Try a new Relay first. Otherwise, and since I don't know what you've jumpered, the Low Pressure Switch won't keep the Relay Contacts closed if the Low Side is below 25 psi or if it's simply disconnected, faulty, or has a lousy connection. If you haven't jumpered it, find it's Connector - should be on the Evaporator Outlet - and make sure it's connected. Then hold it onto the Switch and/or wiggle it around and see if the compressor engages. If so, you need a new connector or switch. Otherwise, get someone to slap some gages on it and if it's above 50 psi sittlng still (it will be if it's fully charged or even if it only has a 8 ozs in it), it probably needs a new Low Pressure Switch.

Too much pressure on the high side is either an air flow or overcharge or plugged up system. Fans should come on around 220 psi with the Factory R12 Charge. If it's been converted to R134, consider getting the PCM reflashed to turn them on around around 170 psi. Any shop should know what the numbers mean, but probably can't help with the reflash.

 

Well, I put some gauges on it and the low side was down to about 10psi
I had to jump the low side switch to get the compressor to engage.
I then added 134a freon(had it converted a few years ago)
The gauges showed 40 on low side and only 80 on the high side. OAT was 85

The a/c was about in the low 40's at the center vent. Light above auto button was solid green.
I went about 4 blocks,got on it a bit and the auto green light started blinking and when I turned it to off the off button was also blinking.
About 40 seconds later the off button was solid green!
Pressed the auto button and it was solid green but no cold air!! Just like before I started!
Any ideas??

 

Did you try pulling code's?

Do you Have an FSM?

What do you mean by "The gauges showed 40 on low side and only 80 on the high side. OAT was 85" Was the engine shut down at this time, the reason I ask is because your "High Side" pressure should be North of 150-175 psi with a full charge, and running.

 

a/c advise is a touchy subject to give exact pressures for diognosis because there are far to many unknown variables that can skew your readings as well as the systems reactions and symtoms, such as amount of oil in the system, outside temp, etc.
so with that risk known both your guages should both read around 100-150# with the engine off and with engine running and ac turned to max should read 20-30psi on low side 200-300psi on high side to be properly charged.

should consult your FSM for the proper readings for your vette and be aware like i mentioned that amount of oil in the system can cause problems as well and most 134a i have seen sold at parts stores contains oil, so every time you top it off you are adding more oil to the system which will eventually cause problems(poor cooling or worse)so really the best thing to do might be to find your leak and repair it first.

 

The requester needs to Articulate.

 

Let me say this: There was incompetence at the controls! Just saying!
Display showed 09 so I jumped the low side switch and added more 134A after the compressor kicked on.
It was showing 35 on the 134 scale and 140 on the high 134 scale.

The 09 on the display is gone.

I'm going to take it for a spin and hopefully it will last more than 4 blocks!

 

Well, I'm back!

The compressor stayed on but it's about 90 OAT and I could just tolerate the temp inside.

It was colder at a stop light than when on the I-10 doing 70 mph!

About 58 degrees at the vent stopped and about 74 degrees at 70 mph!!

I don't get it!!

 

is that 35 on the low side and 140 on the high side? engine off or idle? nice to have both readings off and running at least. also is the compressor cycling or just staying on continuasly durring test?
and just a not its best to test with engine at about 1200-1500 rpm on alot of vehicles.

at the moment i am going to venture and guess your still a bit low on refrigerant. because at the 90* outside temp you mentioned your pressures should be roughly 45-55psi on the low and as much as 250-270psi on the high side while running, but as i said looking at fsm for your specific car would help as these are general readings.. usually close but may not be perfect.
and remember these are pressures for the temp your having right now, colder or warmer outside temps will call for diff pressure readings.

 

That was running at idle. Did not change at 2000 RPM
Low reading was 36 on the 134A scale which is 31 PSI at idle.
High reading was 153 on the 134A scale which is 275 PSI.

I let it cool and checked it again and I had no pressure at all with engine off and very very little with the engine running. I was surprised the clutch was engaging and I had no flashing green light at the controls.
Also no "09" on the A/C control when I checked it. No cold air at all!
So it's obvious I have a leak somewhere which I can't find even though I put dye in the system.
So I'm done!! It's off to the shop! Thanks to everyone for your help!