I went up to the Blueridge yesterday. This morning I got in my truck and turned on the heat (it was a little chilly). It blew like I had it on vent - no heat. I have a mechanical temp guage that has the sensor tapped into the heater input line and it is showing good temp. I used the AC on the way up to Blueridge and it works today, just no heat.

Any quick ideas? I plan on getting out my Chilton's tonight to check it out.

 

Update:
I have had no luck figuring out why I have no control over the temp. My best guess at this point is the reostat that controls the temp - I have noticed that it is free turning without the normal friction it has displayed in the past. I plan on pulling the AC controls out this weekend for a further diagnostic check.

 

T - Did you get this figured out? I have the same issue with my 87 150 not blowing hot air. The AC works fine. AND the Chilton manual I just bought sux. No troubleshooting guides whatsoever. I'm taking the darn thing back.

Let me know. Thanks.

 

I took my Chilton's and pulled the AC controls out of the dash. In the process my son dropped the 9/32 open end wrench into the dash - had to pull the entire dash cover that goes around the instruments along with the outside cover for the Radio/AC portion as well to retrieve the wrench.

After getting the control module out I removed the center rheostat that controls the temperature. Started bench testing and it checked out. Took a look at the ***** (I didn't use the **** in the bench test) and there is a crack on either side of it. When you turn the **** on the rheostat it will not turn the shaft to the heat direction. If it is on warm and you turn it back to cool it has enough grip to turn the control shaft.

I have added a little super glue to get me by but I will stop by the Ford dealership to pick up a new ****.