A/C Woes!

Hi guys,

My 68, 289 with a fresh engine rebuild 5K ago, is having an odd problem. OCCASIONALLY, just occasionally, when I run the air on the interstate ( 70 mph ) the engine will cut out, sputter, and die if I don't cut the air off. Sometimes it will die and is hard to start. The air blows cold, engine runs great. But sometimes this happens. Any ideas? I am afraid to let my wife drive it in the summer because of this. It has happened before the rebuild frequently, but not so much now. The other day it did it while I was doing 45 in town. Thanks for any suggestions.

What was rebuilt? The engine or the compressor? The most likely culprit is the alternator regulator (the "square box" bolted on the passenger inner fender well). Does the belt squeal also when this happens - compressor is locking up. What does your wiring harness look like, from the a/c controls to the underhood harness, check for any shorts to ground, bare wire spots that may happen to ground out. etc.

Thanks MCA,
There is no belt squeal, all my wires are taped up nice and neat, and nothing is bare in the engine. I will check up under my dash.
Do you think I can clean up my Alternator regulator with sandpaper or should I just get another? I will take sandpaper to it, check it out, then try another if it doesn't work. It is the original compressor and "plumbing" all around. It blows cold (not as cold as I would like but it is cold ) and I just charged it last year, so I don't think it is the compressor. I will let you know what happens. Thanks again for the help.......

calgtcsdreamer, i would just buy another regulator, they are cheap enough at NAPA or your fav. parts place! the regulator could be going out on you, not such the matter of corroded fittings! and yes look under the dash for lose wires, when i had my CS i had to clean up some wiring, the wiring had been cut and chopped up from a few different radio's being in there, was lucky that i didnt have a short! good luck and i hope you find the problem ;D

1 GT/CS
Thanks for the tip. My son does work at a part store, you think I wouldn't be so cheap! Thanks, I'll give it a try....

I have replaced my voltage regulator and all my wires are fine under my dash. Now, it only cuts out if I have it blowing on high (third level of blowing). I guess I can use it on level one or two only, but it sure is annoying when it cuts out! Two levels are better than one! thanks to all for the quick responses...

I don't know if this will help but what alternator are you using. The AC cars use a bigger alternator and if you just put in the stock 35 amp (I think that's what it is) you probably aren't putting out enough power. If you have a digital voltmeter, run some wires from the battery to your passenger compartment, hook up the meter and see what your voltage is at speed with the air on high. Just some thoughts
Steve

Thanks Steve, I will post what I find out! AutoZone, here I come.......

Here's a thought. You say the car sputters and cuts out when the a/c is on and when you go to restart the car you say it is hard to start. In what way is it hard to start? If it cranks over rapidly but fails to fire up, perhaps your electrical system is ok and you have a problem with the fuel system.

With the added heat in the engine compartment of running the a/c on a hot day you could have a vapor lock problem. Essentially the fuel in the fuel lines get so hot that it vaporizes in the fuel line before it get to the carburetor.

Check the fuel line routing all the way from the fuel tank to the carburetor to insure that the line is not route close to any heat source -- exhaust system, engine block, etc.

If in doubt, next time the car stops running, before you try to restart it take a peek down the carb and pump the throttle to see if there is enough fuel in the carb to squirt the accelerator pump. DO NOT put your face over the carb while trying to start the engine (this could be hazardous to your facial complexion. Lack of a fuel sighting at this point would indicate a vapor lock problem.