FIX for AC blowing out of floor and defroster vents - ZR-1 Net Registry Forums

402Z · 08-13-2022

Hello everyone,

I was getting the dreaded AC blowing out of the floor and defroster vents no matter what mode I had the HVAC control unit on. I researched and found the typical HVAC controller malfunction, control head unit possibly might not be working correctly, etc.

My radio is not working so I dropped the passenger knee pad panel to access the CDM, and noticed that there was a burnt connector tube that connected two vacuum lines together. I put a pause on troubleshooting the CDM to fix this vacuum line. I was not sure what the vacuum lines were for but after some research they provide vacuum for the HVAC controls that direct what vents the AC will blow out of. Went to the auto parts store, bought a new vacuum line to connect the two vacuum lines for the HVAC controller and sure enough my AC was blowing out of the head vents now. Was very happy that I did not have to mess with the HVAC controller under the driver-side knee panel, or the HVAC head unit. Easy fix!

For those of you that are having issues where your AC is blowing only out of the floor and defroster vents, definitely check under the passenger side knee panel and look for those two vacuum lines. A very easy thing to check before diving into the much more difficult stuff. That courtesy light bulb for the floor gets really hot and could burn your vacuum connector if they are touching which is what happened to me. I will provide pictures of where it is located as well. Hope this helps anyone that has this dreaded issue. Thanks.

Erik · 08-13-2022

Awesome. Thank you sir!

CamP · 08-14-2022

I recently had the same no dash vent issue, but mine was traced to a pinched vacuum line under the plenum.

mlipmd · 08-14-2022

That bulb does get really hot and that's another reason to change it out for an LED. One of these days I'm gonna get around to doing that.

CamP · 08-15-2022

Does anyone have a part number for the LED courtesy lamp? My driver's side is out, so it's a good time to make the switch. The originals do get red hot.

402Z · 08-17-2022

Quote:

Originally Posted by CamP

Does anyone have a part number for the LED courtesy lamp? My driver's side is out, so it's a good time to make the switch. The originals do get red hot.

I'd like to know this as well. Might as well replace it while I have the panel off so I don't have to worry about that light burning anything else.

mlipmd · 08-17-2022

I used these to replace the underhood lights and they fit perfectly and are really bright and that is probably the same bulb as the courtesy lamp. Will have to look that up. I believe they are 578s.
https://www.amazon.com/dp/B07JQDJC1F...g=affinity1-20

You can also get them here, half the price - my next order.
https://www.amazon.com/211-2-1-65in-...a-827612054062

08-13-2022	#2
Erik Join Date: Nov 2016 Location: New Brunswick Posts: 936	Re: FIX for AC blowing out of floor and defroster vents Awesome. Thank you sir! __________________ 1990 ZR-1 # 996 "All Corvettes are red. The rest are mistakes." - John Heinricy

08-14-2022	#3
CamP Join Date: Jun 2012 Location: fort worth Posts: 183	Re: FIX for AC blowing out of floor and defroster vents I recently had the same no dash vent issue, but mine was traced to a pinched vacuum line under the plenum.

08-14-2022	#4
mlipmd Join Date: Mar 2021 Location: Crawfordville, FL Posts: 206	Re: FIX for AC blowing out of floor and defroster vents That bulb does get really hot and that's another reason to change it out for an LED. One of these days I'm gonna get around to doing that.

08-15-2022	#5
CamP Join Date: Jun 2012 Location: fort worth Posts: 183	Re: FIX for AC blowing out of floor and defroster vents Does anyone have a part number for the LED courtesy lamp? My driver's side is out, so it's a good time to make the switch. The originals do get red hot.

08-17-2022	#7
mlipmd Join Date: Mar 2021 Location: Crawfordville, FL Posts: 206	Re: FIX for AC blowing out of floor and defroster vents I used these to replace the underhood lights and they fit perfectly and are really bright and that is probably the same bulb as the courtesy lamp. Will have to look that up. I believe they are 578s. https://www.amazon.com/dp/B07JQDJC1F...g=affinity1-20 You can also get them here, half the price - my next order. https://www.amazon.com/211-2-1-65in-...a-827612054062 Last edited by mlipmd; 08-17-2022 at 01:32 PM.