2nd Gen Non-Engine/Transmission Defrost Only!

[Twisted Shifter]

I have a '94 Auto ... . I was driving home tonight and all of a sudden I had no air blowing on me. I felt up on the dash and the defrost vents were blowing away. I tried to move the switch but it blows on defrost no matter what position its on. The only time it changes is when I put it in the off position and then it goes off. I checked what I could in the dark with no luck.



Pleae help ... ... its hot in FL with no A/C



Thanks



Twisted

 

[PC12Driver]

The hvac dampers are vacuum actuated. So it could be a bad vacuum pump, a bad hvac mode switch (it's really a valve), or something as simple as a cracked/broken vacuum line.



Isn't the cruise control vacuum actuated on the 94s? If it works that would tell you that you at least have vacuum in the lines and it's probably your hvac mode switch. Otherwise, it's just a matter of finding out if your vacuum pump is shot or if you have an open line (both of which would be very possible in an 11 year old truck).



And don't cry to me about the heat; I just had to fire up the furnace tonight for the first time this season. :{

 

[Bob4x4]

Look at your rubber nipples to see if they are soft and collapsing(no pun intended)Check the vacuum line to the cruise servo,another common failure. Make sure you have good vacuum to the vacuum actuator that controls the mode door. That door is located to the right of the accel pedal. It is also not rare for the actuator itself to fail. The default position is defrost.



Bob

 

[Twisted Shifter]

I have cruise ... so thats a good thing? I will try to figure it out tomorrow between rain bands

 

[Twisted Shifter]

I found the pc thats by the fuel pedal ..... If I push it I get air out the dash vents ..... How troubleshot this?

 

[Joe G.]

There is a vacuum connector above the exhaust just before the vacuum line goes through the fire wall. Pull it apart and inspect for a heat collapsed vacuum line. When mine did that it was inside the connector so it could not be seen. All I had to do was clip off the bad place and put the connector back together.

 

[Twisted Shifter]

Joe G. ,



Thank you very much ... ... I went to look at the line you spoke of... ... when I put in the twis I didnt make sure that the line dint touch and its melted so now I know what needs to be fixed ... . thanks again.