I have a 1979 MarkV that I have had since new. The a-c has been recharged and no leaks. Sometimes it blows cool air and sometimes not. It is frosted all the way to and including the expantion valve. Any help would be appreciated. Thanks, Steve

First, I would buy the a/c recharge kit that comes with the servicing hose with it, and that should give you the cool air. You can buy this from Walmart for $34 or less.

It could be a vacume line leak. On most cars vacume opens and shuts the air doors

You can buy a recharge kit for like $30 with the gauge, follow directions. See if it helps most likely you have a leak that's a given but even a very very small leak take time to leak. So for $30 try it if it lasts fine sometimes its just an O- ring or the Schrader valve leaking (the valve you put the freon in thru) check for any oily areas yup that's the AC oil it will tell you sometimes you can't find with ***** eye use special glasses to see, you can find them at the parts store with dye in the 134a it stands out.
Hope I helped
Mike

If it works a little a bit sometimes then not much at others the 134A freon probably needs a recharge.

It may be getting low on freon sometimes they leak out

GO TO AUTOZONE OR AN AUTO PART STORE AND BUT A CHEAP RECHARGER. IF IT DOESNT HOLD IT EITHER NEEDS TO BE RECHARGED PROFESSIONALY OR A NEW A/C PUMP

the air conditioning system has most likely drawn moisture this is not good take it to have the system recovered and a new restrictor valve put in. leak checked and recharged

you still got a leak,could be the ac hose,recharge again but this time w/dye so u can see if theres a leak,good luck keep posted..

There are special cans of R-134A with dye in them for detecting leaks. Most leaks occur around the fittings near the compressor. Recharge the system with the leak detector can or R-134A. There are also cans of R-134A with an additive to stop leaks. I would use these products to either detect your leak or to stop it. Best of luck.
Greg

Hmmm... its gotta be the compressor.