PreGen AC blend door

[alan0517]

Can someone tell me the easiest way to get to the AC blend door on a 95 GP??
The AC will go from vent to vent AND floor randomly.
I have looked all over youtube for some video help.
Thanks for any advise!

[Turbocharged400sbc]

someone may have removed the vac cannister (a plastic ball) or the one way checkvalve on the HVAC line from your SC/UIM vac port.

look for the line that runs into the harness/firewall passthrough and toss one in so that the engine can only suck and not blow (also good to check it doesnt leak (suck on it) in case someone broke the vac cannister (not all cars have vac can fyi)

whats happening is that yer manifold vac drops while accelerating and since the checkvalve isnt there the HVAC system looses vac and the actuators move position. this happens to the digital/vac systems as welll as the older mechanical vac systems.

[alan0517]

Thank you for the reply Turbocharged... I have actually owned this car since it was new and know that the check valve and vacuum cannister are in tact... the weird thing is that it doesn't happen as a result of throttle/acceleration.... actually there is no pattern of when or what makes it happen.... it is random and will sometimes stay 50/50 vent/floor for days then just mysteriously come back up to vent.... that is why I was thinking it may be a weak vacuum or blockage of the blend door???
It also needs head gaskets so I plan to have my mechanic look at all the vacuum while he is doing that... I replaced the vacuum lines that come across and under the throttle body that have the connector/elbow assembly section.... I have replaced all vacuum lines that I can see/reach.... so not sure what else to check.
Thank you again for the reply. Let me know if you have any other ideas??