When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
This sounds like a case of the Ac programmer vaccum system on a 94-96 vaccum liness at the programmer getting soft and weak as the vehicle gets hot. The 94-96 ac programmer vaccum line manifold has rubber tips on them. As the tips age and get hot the tips will collaspe causing blend door to be not be functioning properly. You can take the vaccum lines off and trim the tips off slightly reattach the vaccum lines and see if it works properly. This is not an easy fix as the programmer is in the footwell on the firewall above the drivers feet inside the vehicle. You have to crawl under and look up to remove or repair. Good luck. Gordon Killebrew told me about this problem with the 94-96 models a long time ago.
The vacuum hoses only control the vent door positions. The 94 does not have the collapse hose problem. The 96 definitly does but I'm not sure about the 95.
On the 94-95 the blend door is strictly operated electrically by the programmer and not by vacuum at all. So if air is coming out of the proper vents when the button is pushed in a good flow, you can forget about all the vacuum hoses.
I just went through a leaky high pressure valve, and needed to do all of the research to figure out where my problem was. The temps you're getting out of the vents should definitely be colder depending on the outside air temperature. Not sure if you found this chart in the FSM, but here it is just in case...
Yesterday, Friday, I found the problem, the new part was here this morning and now all is well !!!
I started cranking wrenches when I was 15, in 1958, since then in the 59 years this is the first time I had to do real work on any AC. In the past add a little from a kit and all would be good. I have learned all so much with this problem. Besides the actual mechanical A/C, I learned how to use the C68 control head to do a lot of diagnostics.
I hurt my ears real bad with to much serious gun fire, I wear shooting muffs whenever I deal with loud noise. My 95 has a true dual exhaust with magna flow mufflers from the pre cats back, its loud sitting the shop running, so I have muffs on.
As we know from previous posts, the system ran fine, until the engine got up to operating temp. Then it started to blow warm air out the A/C discharges, before this issue started it was always like a meat cooler in the cabin.
Having exhausted all the diagnostics with no real issues found, yesterday I went out determined to find the insidious problem. In the past when the warm started to blow, I would shut her down and look for a problem. Yesterday, after the engine came up to operating temp and the A/C started to blow warm air, I let her stay running. The compressor had functioned normally with a cool engine. Now I found that with the hot engine, high under the hood engine heat, and the compressor had stopped running.
Per the FSM, I ran a 12 volt line direct from the battery to the compressor clutch. The compressor did come on. I then using electronic circuit board freezing spray, I hosed down the A/C compressor relay. The compressor did not come on. I
then using the freezing spray hosed down the pressure cycle switch. Now being chilled with the spray, the compressor immediately came back on.
I let the engine/compressor run and get hot again, the cycle switch stuck again open and the compressor stopped.
The pressure cycle switch was bad and would fail open in high engine compartment heat. I called my local NAPA, of course they did not have the switch, but got one from the warehouse and it would in in the store, this morning. I was there when they opened and picked up the switch. I also bought a set of high quality manifold all metal gauges.
Came home, installed the new pressure cycle switch and with the manifold gauges checked the system. Per the Corvette FSM, the pressures were normal for 75 degrees ambient. The FSM has a chart of expected air discharge temps. The expected temp at 75 degrees was 36-43 degrees, I had 39. By 1pm, it warmed up to 90 degrees. I hit the interstate and did a 80 mile round trip ride. The FSM shows at 90 degrees the expected discharge temp to be40 to 44 degrees, I had 41, all was back to normal. It was nice having the meat cooler back working again LOL. Also checked out switching from A/C to heat by raising the temp control from 60 to 85 and it worked as expected, lots of hot air, then back to A/C and lots of cold air.
I sincerely want to thank all who replied to my posts. This is a great forum, thank you.
8Valve
Last edited by 8valve; 06-17-2017 at 10:24 PM.
Reason: typo
Now , consider buying as set of gauges, HF - $40, with coupon. It would have showed you the low side was not cycling during the times of the problem. You may not have the problem happening like my info in post 2 which would throw you off if the system was working at the time you checked it.
Silver85/Pcolt
I will make one post. I live very remote in the mountains, my only internet is dial up connecting at 24.4K, and this site is very slow to us dialuppers.
Silver85, you can get the circuit spray at radio shack in small cans or large cans at electronics supplies like freys etc. Comes with a straw so you can aim the blast. The cans says it will chill down to minus 62 degrees.
Pcolt, you must have missed it in my last post. I did buy a set of manifold gauges. All steel quick connects with valves, manifold block machined from a billet aluminum block, and the gauges can be re-calibrated. Only cost 89 at NAPA. I stay away from harbor freight on anything I want longevity or safety.
8Valve
Originally Posted by Silver85
Nice job! Good thinking on the spray. I will have to remember that one!
Thanks for posting the solution. It's a huge help to the next guy that has this issue to see how you resolved it.
06-16-2017, 07:38 PM
