AC blower coming out of floor and defrost, initially

[N2BUICK]

I know this has been beat to death, indoor air coming out of defrost and floor. Mine will finally change position, sending out air from middle vents, as desired.
Trying to find the "root cause" for this malfunction?

 

[pacecarta]

no or low vac on the supply line either from a cracked vac hose or a defective hvac 3port check valve by the firewall driveside valvecover
could also happen if the 9port vac selector valve on the back of the hvac indash controller is damaged

 

[N2BUICK]

In the past I have looked at the vacuum lines and check valve in the engine compartment. I have never tried to check the multi port valve in the ac/heat controller.
If no other problems are seen in the control, do they use a bolt and nut to keep the pieces together?

 

['87 Turbo "T"]

They are held together by a little plastic piece through the center.

If you find a correct hardware set-up I suppose it could work. I cleaned my vacuum selector, made sure it was back together correctly, & added a bit of petroleum jelly to assist in sealing.

Thread 'HVAC vacuum inches'

Jul 21, 2022

Hey guys. Troubleshooting my A/C not coming through the vents. I'm aware it could be an actuator as well as a stuck door.

I have about 13" of vacuum on the line at the fender vacuum ball & 13" where the violet hose connects to the vacuum control switch. However when I switch to NORM, BI-LEVEL, OR VENT I drop to about 7"-8" of vacuum on the blue hose.

My question is this: Is this enough vacuum to actuate the actuators? Figured I should have more if I have 13" coming into the switch. I do hear a small vacuum hiss from the 9 port switch. Could I be losing 5"-6" there?

Is there anyway to...

• '87 Turbo "T"
• Replies: 11
• Forum: General Turbo Buick Tech