Hi guys - I'm new to the forum and new to Corvette ownership, and this is my first post, so I hope I'm doing all correctly... Anyway, I just bought a brown 1974 convertible with a/c from another forum member, and love the car! Problem is, while the a/c works fine, the blower doesn't move enough air to satisfactorily cool the cockpit. I searched old posts and read all about the upgrade to the C4 motor and squirrel cage. I have acquired a C4 motor assy and am having a spacer professionally made by a local machine shop. My question is this: it appears to me that in order to have the room to get the blower motor out, the radiator overflow has to come out. Can the radiator overflow be removed without removing the a/c compressor? Is there another obvious way to remove the a/c blower that I'm overlooking?

Anyway, any thoughts or ideas on this project would be much appreciated...Obviously, I'm trying to make this project as simple as possible, and I would love any input.

Thanks in advance for your help!!

 

welcome to the money pit

not sure about removing the mentioned stuff, but i'll add something to else,

add a heavier / extra ground wire to a good ground point, that will make a big difference as well.

that's all i did on my '72, and it made a huge difference without doing the motor/cage swap.

 

Thanks for the tip! While I'm in there, I will definitely upgrade the ground wire...

 

just did it on a 77, going to have to have the a/c freon vacuumed out, then one bolt on compressor and the aluminum 2 ended hose comes off and now you have just enough room to wiggle out that recovery tank( of course you siphoned out the coolant), 3 bolts(screws) inside the fender by the wheel(easy to find) frees up the tank, put the 2 ended hose back on the compressor to keep the air out of the ac system(not super tight, just on with the bolt sealing the system)
made my spacer out of 3/4 plywood, had to shim it, could have been 1" thick, sprayed it black
used roofing screws for the corrugated roofing that lowes sells, about 1 1/2" long with the metal and rubber washer (perfect), make sure you buy the electrical plug for the new motor, i also trimmed the hose that went into the old motor to the evap housing to make it fit into the new motor, take your time trimming the hose, it can be done
new motor is clocked the same, the screw holes line up, mark the housings(motor and blower housing ) with chalk so you know which holes are for the screws( bunch of holes in new motor housing)
positive wire is real heavy purple,(i did not reuse the condensor , that is for radio static with the blower on)neg is black, you know you have the blower wired correctly when you test it and it is blowing air out the vents and nothing is rubbing, I then used clear silicone on a finger and ran that around the wood spacer motor side and blower housing side(thin rubber glove) then you can put the recovery tank back in and get the ac charged
well worth the effort

 

You may have already checked this, but on the A/C and Vent setting, air should be coming out of the outer and inner dash face vents. On defrost it comes out of the center dash vent near the windshield, and on heat it comes out of the lower vent on the transmission hump. If the air doesn't follow these paths, one or more of your actuators may be bad or the service line leaking. I only mention this because it can also make it seem like the blower is not performing well. All that said, everyone swears by the upgrade, so it's not a wasted effort if it doesn't fix the problem. Good luck

MajD

 

Thank you for the response! I was afraid you were going to tell me that... I was really hoping to complete this project without losing my freon. Oh well, if it can't be done, it can't be done. Thanks again!

 

Thanks for the reply! I just bought the car and was pleased to note that all of the vents are working as designed! And, the a/c is cold, and the fan actually works (in fact, everything on the car seems to work minus the clock!! knock on wood). Anyway, I just thought in these hot Alabama summer days, more air flow would be welcome and I read about the various upgrades, so I plan to do the C4 upgrade and run a larger ground wire. Thanks again!

 

 

 

I changed mine out this spring. Did not have to remove AC lines, but had to remove my compressor from its mount .I have a Sanden style compressor on my 78. After compressor off bracket, removed overflow tank and had just enough room to work the blower motor and spacer in and out. Had to attach the blower cage to the motor shaft once everything was positioned back behind the fender.

While you have the motor out, do everything you can to clean out the evaporator. I used a shop vac and compressed air shot thru the blower resistor hole.

 

only 2 wires, purple(+ controlled by fan sw) and black (- or ground). the new plug you have to use has 2 wires coming out of it, you have a 50/50 chance to wire it correct. just don't crimp or solder until you feel the air coming out the vents. swap purple and black if it is sucking in the vents. you get all the speeds, if you had them before the upgrade

 

Thanks, guys. I'm not sure it will be necessary, but the idea of removing and then reattaching the fan cage to get it into place is something I'm not sure I would have thought of.

 

RR, can you describe this in a little more detail. I'd consider doing this on my '72 a/c LT-1.

 

This is probably a dumb question, but what is the " Sanden style compressor", and how do I know if that's what is in my '74? After my machine shop finishes my spacer (hopefully by this weekend), I hope to get it installed without removing the a/c lines.

 

The C4 blower I bought has the same single tab connector as the C3 blower so no new plug was required.
Just order a blower from an older C4 (84-86 vs 87 on up) and save yourself a little extra work.
Just my .02
Elm

 

So help me out here. I thought I recalled seeing posts on the forum indicating that the squirrel cage was actually the upgrade because the pitch of the blades generated more airflow. Does the C4 blower motor actually spin faster, or can you just swap out the blower motor cage on the C3 motor? Thanks.

MajD

 

something else I ran into, the blend door was not closing off the heater core all the way, that part is a mechanical cable, found that being open by snooping around looking for a blockage, took out the blower motor resistor, the blend door is visible and it was open around 3/4 of an inch when on full cold, there are 2 small screws(already had the passenger dash pad off) by the lever that works the blend door that are slotted, adjusted that but that did not close the door, dug deeper and found the cable adjuster(white) near the heater/ac control levers. now the blend door closes off the heater core. So there is a mechanical cable for blending and then there is vacuum actuators for defrost, floor, and the outer and inner dash vents
I did install one ball valve to stop the engine coolant from getting to the heater core, think it needs it one the other hose also, there was a lot of heat on those hoses that feed the heater core, could have been transfer heat from the headers also

 

Here is a pic of my compressor. I'm sure the Sanden name signifies something, I just know it is th e more modern style of AC compressors used on cars today. Less parasitic drag on the engine when the clutch is engaged.

 

 

Hate to beat a dead horse, but what about the little vent tube going to the fan motor? I noticed my new C4 motor didn't come with that tube, but has two "ports" available for it with plugs in them. Will the old tube fit it, do I reuse it? I assume this is some kind of cooling vent and is important...