Express, Savana & G-Series Vans Offered in both a full size van, or a large box truck, the Express is the modern GM workhorse.

Chevrolet Express
Platform: GMT Van

Heat and AC has a mind of its own...

Old Jul 14, 2023 | 12:53 PM
  #11  
knight13's Avatar
Thread Starter
CF Beginner
 
Joined: Mar 2023
Posts: 14
Likes: 6
Default

Originally Posted by tech2
the door actuators are vacuum controlled and if you have a vacuum leak the doors will change position when the engine vacuum is low...off idle.
do you hear a hissing sound when the engine is idling?=vac leak

Not hearing any hissing.
Reply
Old Jul 14, 2023 | 4:06 PM
  #12  
mountainmanjoe's Avatar
Super Moderator
 
Joined: Feb 2017
Posts: 6,207
Likes: 689
Default

The HVAC system needs to be able to hold a vacuum even when there's positive pressure in the engine intake.
Shut off the engine and wait a few minutes. Then test if there's still vacuum on the source line.
Reply
Old Jul 18, 2023 | 5:50 PM
  #13  
knight13's Avatar
Thread Starter
CF Beginner
 
Joined: Mar 2023
Posts: 14
Likes: 6
Default

Anyone have a source for a safe place to purchase a service manual so I can dig into this a bit more? Tried the normal Google search for a vacuum diagram and not have any luck yet. eBay only shows me a service manual for over $300...

I'm planning on spending a bit of time with it this weekend to see what I can uncover.

Ed
Reply
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Agates21
2007 - 2013 (GMT900)
5
Sep 29, 2025 7:15 AM
Ricky Mccurry
1999 - 2006 (GMT800)
0
Apr 23, 2019 4:10 PM
Boverman93
Traverse
1
Jan 7, 2015 11:32 PM
kels2kara
Silverado, Sierra & Fullsize Pick-ups
2
Jul 18, 2010 4:37 PM
dsjacr
Silverado, Sierra & Fullsize Pick-ups
0
Oct 6, 2009 8:24 AM


Thread Tools
Search this Thread

All times are GMT -5. The time now is 1:12 AM.