C3 to C4 a/c Blower Upgrade
#1
Intermediate
Thread Starter
C3 to C4 a/c Blower Upgrade
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!!
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!!
#2
Melting Slicks
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.
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.
#3
Intermediate
Thread Starter
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.
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.
#4
Instructor
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
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
Last edited by george2066; 07-09-2018 at 09:03 PM. Reason: added a step
#5
Racer
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
MajD
#6
Intermediate
Thread Starter
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!
#7
Intermediate
Thread Starter
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
MajD
#9
Safety Car
On my 73 I can remove the overflow tank without removing the ac lines. Well that was with the old style compressor as well. I ran a larger ground wire from the C4 blower right to the intake where the coil is bolted on. I pickup the correct fan plug at NAPA. I used the same relay as the C3 blower and spliced in the plug. I ran a larger wire from the high speed relay to the blower motor when I did the hookup.
#10
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.
#11
Instructor
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
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NRAROX (07-11-2018)
#12
Instructor
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.
#13
Le Mans Master
Member Since: Feb 2001
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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.
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.
#14
Intermediate
Thread Starter
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.
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.
#15
Drifting
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
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
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shurst (07-11-2018)
#16
Racer
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
MajD
#17
Instructor
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
MajD
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
#18
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shurst (07-12-2018)
#20
Intermediate
Thread Starter
Vent tube
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...