98 blazer heating problem.

[g8t255]

Hi. I have a 98 blazer with the computer controlled heater. My problem is this: The heater blows really hot air on max heat set to the defrost position. If you turn it to any other position, be it vent or floor, the fan slows right down but the heat stays hot. In addition, if you turn anywhere off of max heat, even a click or two the temp goes way cold. Any ideas? I am thinking it might be the module mounted to heater box under hood?

[MT-2500]

Originally Posted by g8t255

Hi. I have a 98 blazer with the computer controlled heater. My problem is this: The heater blows really hot air on max heat set to the defrost position. If you turn it to any other position, be it vent or floor, the fan slows right down but the heat stays hot. In addition, if you turn anywhere off of max heat, even a click or two the temp goes way cold. Any ideas? I am thinking it might be the module mounted to heater box under hood?

Auto matic heater controls?
Battery been changed or a dead batter witha a jump start?
Try the relearn procedure.

If that does not help you may need to get it on a HAVC body heater control capable scanner and see what is going on.
If any HAVC /heater control codes post back code no.

[g8t255]

Thanks for the reply. I did change the battery this past summer but no boosting. How do you do the re learn on this truck? I just learned how to do it on my Caravan but not sure how on the 98 blazer.
Thanks.

[g8t255]

Sorry, Yes it does have auto heater controls. I will see if my local parts source has the havc code reader.
Thanks.

[MT-2500]

It may not have the cry type relesarn.
But computer can be reset by pulling the fuse or disconnecting the neg battery a few minutes cable and phooking it back up.
But first check and clear codes and see what comes back also watch havec operation on scanner.
Most parts places do not have scanners capable of checking HAVC.

Good repair shop with a good trained tech/mechanic is best bet on that end.

[g8t255]

Thanks. I will give the negative cable a try and see what it does. I will check with my local GM dealer and see what they would charge me to scan it.