djhuge

I just spent too much paying a mechanic to reactivate the AC unit, including new hoses and whatnot. The air is cold-er but not super cold.
However, the speed on my fan seems to be a little low.

Now I don't know whether it's resistor (speed 1 and 2 are very weak and that's why I think so), or perhaps the blower motor needs replacing. Or perhaps the fan speed/strength on a 75 isn't really that much.

If you were to characterize a proper outflow of air from the central consol on the high setting - could you distinctly feel it on your face, or is the whole set up not that strong?

Also, what do i need to remove to get to the blower motor - any body has suggestions/photos.

Thank you for your help

SIXFOOTER

OK, first off. all those are very subjective assesments. What I would do, is go thru it by the numbers.
1. Verify the resistor pack is good, measure the voltage at the blower to ground at each speed selection
2. Measure the ground connection from the fan ground wire to frame ground
3. Hi Speed voltage should be very close to alternator output voltage.
4. The fan is removed from under the hood, its a PITA, there are 5 or 6 small screws holding it in place, passenger side firewall. Make sure it spins freely, the bearings dry out and it is stiff sometimes, some good oil will resolve that.
5. On to the ducts, there are probably several leaks, close them up with weatherstrip foam.
6. There is probably a large gap between the lower duct and defrost duct, close it up with silver foil tape if you can find it.
7. Verify all the duct doors operate with the selector switch.

SanDiegoPaul

I rebuilt my AC part by part, two summers ago. It woke up using all new parts. No reman stuff; all new including the compressor, hoses, evaporator, POA valve. All new but the switch.

I had `ok' air but that was about it. Then I took the dash out, and resealed the ducts inside. From that day one the AC blew twice as much air and it feels fine to this day.

Also, insulate the floor. Reflectix insulation will allow the cockpit to be much cooler inside, so the AC has a chance of making passengers comfortable. With the cabin being overheated by floor heat constantly, the AC would need to be twice as big a unit, to cool properly.

djhuge

I insulated the entire floor and doors of the cockpit and it's definitely cooler in there. It's interesting to hear that checking for leaks makes a difference. Are there any particular tubes I should check for leakege?

I'm Batman

Tubes? You need to be checking the ducts and air control doors for leakage. The "Search!" sticky is your friend...there are numerous threads on eliminating cabin heat.

Red 69

I believe my 79 does what you are describing happening with your 75. My AC/heat blows strong on high, but drop the switch down and the fan seems to stop completely. If this is you problem, we both need the same fix. Pictures are better than many words.

djhuge

However, I'm having hard time finding the resistor. Is it the small metal box attached to the evaporator box?

jnb5101

i'm installing a 76 a/c unit into my 70. The blower ressistor exits the 76 evaporator box on the top. its got 4 connectors. check your ground connection on the blower motor. also, do as sixfooter recommended, and seal the gap between the inside heater box extension (held in by two screws to the main heater box) and the defrost vent. i had a 1/2" gap all the way around mine. you'll probably have to drop the right side dash panel to access this stuff.

BerniesVette

On C3s, the only position the A/C will blow cold air without mixing it with outside air is the MAX Air position. You can install a C4 fan cage in the C3 which has longer blades that pull more air thru. A 1/2" spacer must be made to accomodate the longer fan. Their are several threads in the archives on this.
Bernie

Red 69

Thanks for the info, but my fan blows air fine, but only on high. I removed the A/C compressor belt for racing, so the fan is now only used to add additional engine cooling through the heater. Again, it only works in the high position. I looked through my 79 shop manual for help, but it only mentions a relay and doesn't show its location. It would be easy enough to fix if the faulty part could be identified and where it was located. Initially I thought it was a bad switch, but now I'm not so sure.

I'm Batman

You need the 79 Corvette Electrical Troubleshooting Manual (if they printed one). Here is a 78 version on eBay: http://cgi.ebay.com/ebaymotors/1978-...spagenameZWDVW

SIXFOOTER

Thw resistor in on top of the evap box on the passenger side of the firewall, the Hi Blo relat is right above it

Red 69

Thanks...that was easy to find! I was following a source that said the relay was next to the fuse box. When I get a chance I will test it to determine if it is my problem.