issue with HVAC diffusers not switching positions.

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Jun 18, 2024 | 02:30 PM

Jayboost99

Thread Starter

4th Gear

Joined: Jun 2024

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issue with HVAC diffusers not switching positions.

Hello All!. I have a 99 and the issue is the vents don’t switch positions. The Control works fine. When I run heat or A/C the air seeps out from every vent just a little bit and it isn’t efficient at heating or cooling. The car has no HVAC codes in the onboard diagnostic but it does have an air air system codeP0410 and also P1416 Air system bank 2. Anyone ever have a similar issue with their C5? Thanks

Jun 18, 2024 | 04:30 PM

ipuig

Drifting

Joined: Jan 2008

Posts: 1,722

Likes: 138

From: Florida

St. Jude Donor '09

Quote:

Originally Posted by Jayboost99

The vent actuators are vacuum operated. There is a vacuum line that powers the actuator control that runs from the rear of the intake manifold under the battery to an HVAC vacuum system reservoir and to the the HVAC actuator control located in the passenger footwell through the passenger side bulkhead. Its a common defect; you will have to replace or repair the damaged vacuum line. You will find many posts on this subject, I recommend you use the search function.

Jun 18, 2024 | 04:51 PM

bookyoh

Pro

Joined: Dec 2014

Posts: 683

Likes: 275

From: Cincinnati Ohio

As ipuig wrote, there are any threads on this issue. In the last one or two months, a Forum member went down an excellent diagnostic path, with photos, to solve his issue. His problem seemed to be much rarer. He had a good vacuum source and good vacuum through the lines. In his case, it was a solenoid which opens and closes vacuum to the actuator.

Sorry that I don’t recall who the Forum member was but a search of C5 Tech will find it.

Found the thread: https://www.corvetteforum.com/forums...readid=4833273

Last edited by bookyoh; Jun 18, 2024 at 05:29 PM. Reason: Found the thread

Jun 19, 2024 | 08:21 AM

Jayboost99

Thread Starter

4th Gear

Joined: Jun 2024

Posts: 4

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Thanks for the good info! I’m going to start checking all the vacuum lines.

Jun 19, 2024 | 08:54 AM

grinder11

Race Director

Joined: Oct 2004

Posts: 12,864

Likes: 4,667

Many threads on this common issue. Sadly, the C5 mixes both electronics and vaccum in the HVAC system. Hence there is some confusion. Not disputing the other posts, just trying to provide some clear info. Air temperature controls are usually the electronic air actuators/air dams. As in one side is hot while the other is icy cold when controls are set to cold or hot. Distribution is usually vacuum. As in having the dash vents selected, but air comes out at the foot level vents, or the defrost vents. Also, some codes only show while the engine is running. Hope this helps...