brian76

Probably been a million threads on this, but I still have question. I put a C4 fan in last year with a spacer to move more air thru the vents. The new blower works fine, in fact when I turn it on high , I can really hear it working in there. But barely, and I mean barely does any airflow come out of the vents, I even removed the drivers vent off by the trans tunnel, and still didn't feel hardly anything. This tells me something's blocked in there. I was wondering if I took the blower motor back out , and blasted some air in there from my air compressor if it would unblock anything? Or blasting air down the blower hole? Or vacuuming either way? I don't want to take the whole thing apart, Yeessh! Thanks, Oh I have a '76

JETS C3-C4

Is the rotation of the C4 fan/motor the same as the one you removed?
Just a thought but something you should check for rotation/airflow direction.

MajD

When you say "driver's vent off by the transmission tunnel"?, do you mean the floor vents under the center of the dash? If so, then I would agree that you have a blockage, provided you checked the airflow with the selector on "Heat". If there is no airflow from that vent when the selector is set on heat or a/c, the blockage is in or before the heater box.

I don't know how well blowing compressed air will work. There are a lot of convolutions and turns between the blower housing and vents. The air travels either through the heater core or the evaporator, so I would think blowing air from either direction would eventually force the debris against these. One thing you could try is to set the climate control to vent and switch the temperature setting between hot and cold. If that changes the airflow, then you know that either the heater core or the evaporator is clogged. I can't think of a way to clean it out without removal. Good luck.

MajD

brian76

You know , I'm going to try this. If reversing the wires will make it work, well, I'll be the biggest dumbass in the state. I even hooked up a larger ground, because I've read that it makes the blower turn quicker. I'll try this and get back to you!

bobs77vet

maybe its not reversing the wires but reversing the physical unit, some times reversing the wires doesnt make a diference

brian76

What do you mean," reversing the unit? It only goes in one way. Do you mean reversing the fan? Thanks, Brian

hgoodwiniii

I am having the same issue with my 76. Here are a couple of threads you might find helpful.

https://www.corvetteforum.com/forums...ll-vacuum.html

https://www.corvetteforum.com/forums...w-from-ac.html

Hammerhead Fred

My guess:
Low/no air flow could be from debris (leaves, nest, etc) blocking the evaporator. Unfortunately the only way to clean it is to remove the A/C cover on the engine compartment side. You can try sucking it out with a smallish diameter hose taped to the end of a shop vac. I doubt blowing it around with compressed air will resolve anything.

Had the same issue with mine but even after sucking a great deal of material out using the shop vac method I found that the evaporator core was still almost completely sealed by +40 years of debris sucked into the system once I removed the A/C.

hgoodwiniii

Is there a write-up that describes what it takes to actually remove the AC cover? I think I am going to ahead and remove mine. I have removed some debris with a shop vac.