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Poor A/C Performance In Later C3's

Mar 9, 2009
The later C3's are well known for their poor A/C performance and here's two pictures that show why. The blower wheel inducts it's air from the right side of the windshield wiper plenum and there is a flimsy plastic screen that covers the air intake that is SUPPOSED to stop leaves and other debris from getting sucked in and shredded by the blower wheel. The problem is the OEM screen doesn't fit well and allows leaves and other debris to get sucked in UNDER the screen where it then gets pulverized and blown against the face of the evaporator core. When the evaporator in my '82 sprung a leak 10 years ago I removed it and sawed it in half and found the debris had reached the middle of the 3" thick core.............1-1/2" deep! And it's those leaves and other debris that limits the air flow thru the core and interior vents. After I installed my new evaporator I removed the plastic OEM screen and made a new one using 1/8" hardware cloth then used black RTV to seal around it's circumference. With my new screen RTV'd in place leaves can not get thru any more

My '82 is garaged whenever it's not being driven and look how much debris (including string) that is resting against the outer face of my new 1/8" hardware cloth screen. Once leaves and other debris get into the plenum the only way out is thru the left side or right side and the blower wheel gets it's air from the right side (see the problem?).

If you still have your original plastic screen and park anywhere near trees you can be assured your evaporator is plugged solid like mine was.


  • 1982 Corvette Blower Wheel Plenum Screen 001.jpg
    1982 Corvette Blower Wheel Plenum Screen 001.jpg
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  • 1982 Corvette Blower Wheel Plenum Screen 002.jpg
    1982 Corvette Blower Wheel Plenum Screen 002.jpg
    249.6 KB · Views: 127
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I turned mine inside out in 2002 and found the inside of the ac ducting nor down below the screens any debree. Besides from alot of dust nothing found it's way into my ventilation ducts and evaporator. The problem on mine was the coolant switch wasn't working properly leaving it open for some degree (problem in the vacuumswitch not pressed correctly)

Btw. Isn't facebook a good idea to post all your c3 live lessons? It would make alot more sense to me the overhere to be honest :)

Greetings Peter
Does your '81 also have a black plastic "screen" on the right side of the wiper plenum? I would think the '81's and '82's were made the same in that area and if so the face of your evaporator would also be plugged. Can you take a picture of the right side of your wiper plenum so I can see if it resembles mine (or the way it used to be)?

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