1998 Chevy Blazer AC & Heating Problems

I have a 1998 Chevy Blazer. It has 50,00 miles on it and the battery light turned on. I took it to a local mechanic to repair it. He changed the alternator and the battery light turned off. When I picked up the car I instantly noticed hot air blowing from the heating/AC vents inside the passenger compartment even though the cold setting was selected. I tried changing the temperature controls on the dash to every possible selection, including AC. The only way can get the hot air to stop blowing is by turning off the fan switch and even then hot air still wafts out. I would like to know if anyone has experienced this problem (about the hot air blowing from the vent).
I would also like to hear any input about the responsibility of the auto mechanic who performed the work. I feel certain that the problem is some how related to changing the alternator.
Any suggestions on what the problem could be and how to deal with mechanic would be greatly appreciated.

Thank you
bssperr

Changing an alternator shouldn't affect your heating/ac. You should take it back to the mechanic, explain the problem, and see what he says. At the very least, he should check over his work and look for any possible problems he may have created. If he did make any problems, then should repair it free of charge. But as I said earlier, I don't think the alternator would cause your problem. There are only two wires that connect to the alternator, the lead to the battery and another small harness the plugs into it. I just suggest you ask the mechanic to check his work, don't be mean to the guy though. Everybody makes mistakes. If he gives you the rundaround, and what I mean by that is him telling you to buy all kinds of parts and services that do nothing, then take him to court and sue for malpractice :icon16:

I Have The Same Problem With My 1998 Blazer.
The Problem Started After I Tried To Jump Start My Truck When My Battery Died. Then I Put On A New Battery And Scince Then I Am Having The Same Problem You Have. To My Opinion It Is Responsability Of Your Mechanic.

I Havent Solved The Problem Yet. When A Do Ill Be Writing It Here.

A Temporary Solution Is To Change The Water Hoses From The Heater To Prevent Hot Water Running Thru The Heating System.