85 Jimmy. No emission components. Trying to diagnose my defrost. Or lack of. I’ve got a vac line coming through the fire wall in the engine bay near the heater core and don’t know where is goes. Any help would be appreciated. Pic provided.
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
Mystery vac line.
- Thread starter Bcwkyle
- Start date
Thats probably the vacuum supply line going to the heater controls. Its also probably why it wont switch to defrost. Those usually T into the other vacuum lines and attach to the intake or carburetor base.
If that line enters the interior through the firewall it is the hvac vacuum source. Hook up to manifold vacuum.
Should be a round plastic ball on driverside by wiper motor post 80 trucks or passenger side pre 80. This is vacuum reservoir, allows short wide open throttle operation without hvac doors changing. Not 100% necessary to have ball.
Should be a round plastic ball on driverside by wiper motor post 80 trucks or passenger side pre 80. This is vacuum reservoir, allows short wide open throttle operation without hvac doors changing. Not 100% necessary to have ball.
If that port has high vacuum at idle it's just fine.
Easy fixes are nice.
Don't forget to attach the vacuum line to the switch for the transmission.
EDIT: the can you show on the firewall is probably the "tip-in" switch. The ESC system supposedly pulls a little timing on a bigger throttle opening.
EDIT: the can you show on the firewall is probably the "tip-in" switch. The ESC system supposedly pulls a little timing on a bigger throttle opening.
Last edited:
