I own a 97 expy eb last year I replaced the heater core. TEARABLE JOB, anyway it's now 95 outside and now the heater will only blow hot air. I can touch the box under the dash and feel that it getting cold but I only get hot HELP Thank You

 

I don't know if it's the blend door or the actuator anyone have some advice?

 

Try these ideas first (from my FAQ at another site)

Symptom: Loss of control of temperature. May be stuck in one position or may flop open/closed with vehicle motion when starting/stopping.
Problem: Broken Blend Door
Solution: Replace blend door. Requires removal of dash. There are several threads that deal with this.

Symptom: Can’t change temperature on a manual-control system. Easily confused with a stuck/broken blend door.
Problem: Stripped Temperature ****
Solution: Replace **** with a new one from the dealer.

 

try pulling the fuse and reinstall, it worked for me.