I have a 98 F150 V6 with AC and it hasn't blown heat in the last month - I took off the control switch to see if it was cracked (suggestion by prior post) no cracks. I then took off the panel below the dash and looked at the blend door actuator (another suggestion) the actuator seems to move freely and rotates about 1/4 inch. I would like to see if I may have either a bad/plugged heater core or a bad thermostat. Some of the other diagnostic things I have done is I drove home the other day and checked the hoses after my 5 mile drive - main radiator hose was hot - one of the hoses to heater core was warm - not hot and the other was not even warm.

Any ideas of how I can test to resolve my problems. Thank you

Silver Bullet

 

I know this is really obvious, but I fell for it too...

Have you checked your coolant level? I went for several days with "cold" air on my mustang... Ouch!!

 

You know I haven't lately - Good idea - Solved my problem. I feel pretty stupid I didn't think of that first. I assumed since my truck wasn't running hot that I had enough coolant in but you know what assuming does.

Silver Bullet