Why is vacuum on all the time at heater valve?


Active Member
Jul 17, 2020
Reaction score
Cleveland, OH
Yes, its me again but now the vacuum won't turn off, so I made another post in order not to confused anyone. Previous to this, I found the vacuum line disconnected at the vacuum reservoir. I guess I accidently dislodged it when I was installing new heater hoses. But when I attached vacuum line, I noticed vacuum now is always on which means when I tried the A/C, hot air blows in. (Only A/C vents work, so when I put on heater, heat comes from A/C vents which is fine with me.)

As I stated in my previous post, the dash was rotted when I got it. Vent doors either don't work or are rusted/frozen, so they don't actuate. In the summer, I disconnected and plugged the fresh air actuator vacuum lines (circled) since door would always open to fresh air, which means the A/C doesn't work as well as recirculating air. Since vacuum is off at that actuator, door is closed to fresh air and set to always recirculating now.

Anyhow, anyone know why vacuum is always on? Is it because I disconnected those fresh air actuator lines or a bad vacuum regulator? What does the time delay relay do? I'm still not hearing any vacuum sounds when I push the buttons in, should I? Thanks to all since I'm not very smart.

Thanks to David Hill for the pics.



Illegitimi non carborundum
FCBO Gold Member
May 21, 2013
Reaction score
Marcellus, NY
Again, I'll say that the usual problem is the vacuum switch.

A lot of these questions about "what does the time delay relay do" can be answered by reading through the AC sections in the FSM. Download a free one here: Service Manuals – MyMopar

No such thing as "I'm not very smart". Nobody was born knowing this stuff.... Just gotta plug away at it.