C5 AC Control Unit testing
Thread Starter
1st Gear
Joined: Jun 2022
Posts: 1
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C5 AC Control Unit testing
Is there a way to test the AC/heat head unit for a C5 auto control ? Replaced blower motor and control module & all wiring has been tested but still just very little air coming out of vents..
Greg -
Greg -
Safety Car
Joined: Mar 2017
Posts: 3,771
Likes: 940
From: Orlando Florida
Anytime I see a post with "very little air coming out of vents" I have to wonder if the HVAC vacuum source is intact. Forgive me if you're already familiar and have verified this, but the HVAC system has two primary control methods, using vacuum actuators to control the air flow path and electric actuators to control the air temperature. If the system doesn't have a good vacuum source, the actuators default to a kind of mid-location with air blown out all the outlets at the same time, including the dash, defroster, floor, etc. Even if the blower is actually running full steam, there just isn't enough volume for all the exits. The problem is very common and can be a pain in the butt to rectify.
If your vacuum is good, then on another thread C5 Diag is working a similar issue with UselessC5 (and to which I've already glommed on):
https://www.corvetteforum.com/forums...ermittent.html
Really good source for vacuum source information:
https://www.corvetteforum.com/forums...with-pics.html
On my '99 the plastic vacuum tube was broken AND the vacuum reservoir leaks. I bridged the broken and missing tubing with nominal rubber vacuum line and bypassed the leaking reservoir. Works great, except at large throttle openings, when I lose air path control.
If your vacuum is good, then on another thread C5 Diag is working a similar issue with UselessC5 (and to which I've already glommed on):
https://www.corvetteforum.com/forums...ermittent.html
Really good source for vacuum source information:
https://www.corvetteforum.com/forums...with-pics.html
On my '99 the plastic vacuum tube was broken AND the vacuum reservoir leaks. I bridged the broken and missing tubing with nominal rubber vacuum line and bypassed the leaking reservoir. Works great, except at large throttle openings, when I lose air path control.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,615
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From: Cape Coral, Florida
What year is the car ???...any DTC's ????....auto or manual AC ???
Last edited by C5 Diag; May 10, 2023 at 12:18 PM.
