If Vintage air and hot rod air are both closed cabin units.
This would mean you have to block off the little side vent
on the pass, kick panel. OK, no biggie. The factory units suck
because the vent on the pass side kick panel never close correctly
because of age or high speed. High speed meaning, forced air from
the cowl vent to the kick panel vent can force it open just a little.
then you got the blower motor that sucks to. then you have the A/C
vents that are to large, (duct).

OK, so back to the top, What if you block off the side vent.
Got smaller duct on the air vent.
Put a C-4 blower motor in.


This would be like one of the aftermarket units, would it not.
I did not mention the heater because we all know about a
on/off switch on the heater line to keep some heat out the
cabin.
If you think about it, a well insulated cabin with these minor
changes would work just like the aftermarkets units at less than
half the price. I was going to get a hotrod air unit, but found a
corvette book that shows all the flaws on C-3 cooling, the biggest
problems were the side vent,and the big ducting that needed to be
down sized, and the blower motor not having enough finn's to blow
fast air.

SO, someone tell me why this would not work.
I think these changes would work more than well
even with a closed cabin. Give me some input

 

I am trying to figure this out also. On my 68, on the passengers side, air can come into the fan from the extreme right side of the wiper well, the vent (if open) or the kick panel vent (if open or leaking). I agree with you, if the kick panel vent was blocked there is still a lot of places to draw air from.

I am rebuilding my damper doors for the kick panel now and I am trying to figure out if they are even useful. Anyone know the airpath for modern cars? Do modern cars even have kick panel vents?

MEGLADON, what is the A/C book you are reading?

 

South Side: I think that your overall AC system assessment is accurate. You have identified some of the major shortcomings of the C3 AC system. Lots of posts recently about upgrading the C3 blower fan with a C4 fan. Diagrams and instructions for upgrading the blower fan have recently been posted. The feedback and results have been positve.
Either closing off the kick panel vent door, or making sure the door is working properly, are essential to getting max benefit from your AC unit.
It is also critical in my opinion that all the numerous improvements to keep heat out of the interior compartment be done in order to obtain max benefit from the AC--otherwise it will still be hot in your corvette even if the AC system is working correctly. It is a dual problem.

 

My input (FWIW),
If your kick panel vent is not closing completely replace the rubber seal around the door or check the vacuum actuator. It should shut completely at 6" of vacuum.
I don't agree with the size of the ducting. In vettes that I have frame-off restored, after replacing ALL of the seals with the proper ones (Doc R.) and properly aligning the ducts, the airflow was great. Realize that the electrical connections to the AC relay as well as the console contacts were fresh and did not drop voltage like corroded parts will. Yes the C4 fan has deeper fins, but if the fan is only getting 9 volts in high, fixing the electrical system will benefit you also.
The recommendation about sealing the kick panel would not benefit as much as sealing the cowl inlet. Sealing the cowl vent would put the system in constant recirc, or MAX, cooling constantly reducing cabin air instead of constant temperature outside air. Modern vehicles still utilize some kind of recirc. path (ex. my new Town Car) so it is useful to be able to select alternate sources of vent. air.
Sorry this is so long.

 

Missleman, are you aware that at speeds over 55 the side vent
open slightly! even if rebuilt to spec's or better. this is what's
going on.

I will dynamat the whole cabin and doors and firewall inside.
Dyamat has another deadener you can apply over that to.
kinda looks like a thin foam but effective.
I was going to go with HOTROD air, but this book is kick ***
and tell's you every problem to a t, the ducts in the C-3 are to big
and smaller would work better. $1000.00 is what hot rod air wants
for their set up, so for under $100.00 I will take more time out to modifiy
what I have, to work way better. I understand all hole's and cracks
have to be sealed, to keep hot air out, But I think If I made it a closed
cabin, the air would be constant cold and with much more comfort

I would rebuild the side vent, but I cant drive 55
Once back on the road, its going cross country, Don't
care where we go, just far from home

 

I agree with Missile there, but having said that, I think the placement of ducts in the early C3 was less than optimal...to say the least.....I pulled the pipe to the outlet on the driver's side, and never put it back....don't freeze my knee that way...
need to block some of the flow though...no biggie, when I get around to it....in 3-4 years maybe....;-)))

the C4 blower on spacer is a definate improvement....and so with my convertible, I get quite enuff air incursion, so don't care one whit damn about that sealed door under the cowling there....or the missing interior deflector door either....

like I said, it's a hotrod, nuttin' stock....nuttin'....

GENE

 

GENE, I don't want anything stock either

 

The Vintage Air A/C is for adding A/C to non A/C cars. Yes, if you fixed the system you have, you should be fine.
Would you believe I modified Max. on mine in the 70s to allow the blower speed control to allow speeds instead of just High in Max.
We do have less interior volume in the early ones 68-77.

Check the evap. box sealing under the hood. GM is known for good A/C & normally have fresh (normal) A/C & max. (recir.) positions.
Missileman is probably on target.

 

"I was going to go with HOTROD air, but this book is kick ***
and tell's you every problem to a t, the ducts in the C-3 are to big
and....."


Again, what is "this book" you refer to? I hate to keep asking the same question but I would like to get it.

 

BBSHARK sorry, I will scan the cover tonite and post it tomorrow
for you. its a book on wind noise and poor A/C on C-3's

Mid America show's a copy on page 9-16.
the cover has a red 80/82 front shot and
the top sez, corvette water leaks and wind noise solutions $19.95
this is a graet book
don't know how old my book is but the catalog # 133g (midamerica)
Im sure you can just find the book section and there it is

 

MEGLADON: Thanks, I just ordered it from Mid America (still available).

600-029 Wind Noise and Water Leaks Troubleshooting Book

 

After the tips above are implemented, if you still have warm air (or not cold enough air) try these:
1. Make sure that the accumulated leaves and other debris are removed from the evaporator box. Duct tape a 1" hose to your shop vac and snake it down the cowl vent hole. Wiggle it around gently and you'll be amazed at the crap that comes out. This will allow more air to flow thru the evaporator. No matter how big the fan (C4 vs C3), if the evap core is clogged/blocked, not enough air will come to the cabin.
2. Insulate the engine side of the evap box. Manifold temp is about 1000 deg F only inches away from the air you are trying to cool to 50 deg F. This condition is even worse if you have headers since they will almost kiss the evap box. If possible, place this insulation on the inside of the evap box so that it will not deteriorate with time. Koolmat will insulate best for a given thickness of insulation.
3. Install footwell heat reflectors from a 69.
4. Seal all firewall penetrations - include clutch and shifter seals.
5. Insulate AC hose lines.
6. Insulate AC accumulator.
7. Clean the ground connection on the fan (both ends).

If you do all the above with a floor insulation job, a trans tunnel insulation job and a functioning AC, you will be WAY cool.

 

I like your idea of having fan speed control in MAX(recirc) - care to share any tips for doing this? I haven't yet taken a look at the wiring diag. IMHO the MAX setting should just control the recirc or fresh setting and driver should be able to turn the fan to any speed including OFF.

I've always thought GM historically did good solid HVAC - but now that I've dug into an early C3's HVAC - why did they go so wrong w/ the C3?




Good suggestion about the box - I think it can also be reached thru the passenger kick panel. Ironically if you remove all that crap - may have more heat reflect up thru the bottom... but get it out nonetheless.

What's special or unique about '69 heat reflectors? Are you talking about the metal sheets that were mounted to the outside of the footwells below the firewall w/ an air gap betweeen the fiberglass?

Insulate the AC hoses and accumulator? I don't understand what you are trying to accomplish there that has to do w/ heat buildup in the interior?

 

Yes, that's right.
Blower speed control on Max.
It's just a matter of disconnecting the high blower relay wire from Max. & connecting the blower switch wire at Normal A/C to Max. also.
Changed that & Low to Off on mine a long time ago.

 

Maybe someone can help me with my 72. Sometimes the compress comes on when switched on and sometimes it dont. The switch on the controls seem to be working OK, but it seems there is another switch somehere under the dash--relay?? If you put 12 volts to the compress it will come on the sometimes stay on. Then you can use the switch normally for a while. If you leave the AC control on it works and if you turn it off it might or might not come back on. I had a old time AC guy look at it and he said it should work. He does not see any reason for it not to come on. He thinks it is a switch or relay that is under the dash that the wiring guides show. Any suggestions? I have insultated the car and sealed the leaks and it works well, but if it would JUST COME ON when I wanted it too it would be great!

 

You need to do more troublshooting on this. Connect a volt meter to the wires going to the compressor and see if you get 12v all the time of if it drops out. Best would be to put the hood down and drive around some side streets while watching the volt meter.

You also may be low on refrigerant...have you checked this ? I would check this first before checking the 12v to the compressor.

 

FLYNHI, are you talkin about my idea, or the tips everyone is
suggesting?

this is how I see it, 2 companys sell only closed cabin A/C systems.
Why not just fix the small problem with the stock unit, and make it
a closed cabin also? The only reason I say closed cabin, is because
the trap door will still let warm air in at highway speeds. even when
these car's were new, this happend. I just want to make sure there
is nothing different about the unit that would not allow this. (stock unit)

 

I'm with Pete76Shark on this. Sounds like voltage drop to the compressor coil. Not enough to draw it in, but enough to hold it once it's engaged.

Hans