Anyone actually done this yet?

I am thinking about it now since my AC is working. My original blower is working and is quiet but I think during the summer, its gonna need more flow to cool this new black vinyl interior down.

I know we have a make a spacer for out of cutting boards, what about the wiring? can I not just use the factory wires and relay? they are already thick gauge wire with a seperate relay so...??

Is this mod worth the effort?

TIA

 

Lot of them done already, factory wireing and relay works. From all reports well worth the time and $

 

This is something I am working on as well. I believe it to be well worth it.

The C4 fan is not really all that much more powerful, if at all, but it's fan cage has more blades, at a more radical pitch, and an inch more on the long end. It just moves better air.

To get the most out of that motor, use a relay and the 14+ volts from the alt's BAT terminal.

Use a relay, four pin, that's switched on by the original wire, and powered by the alt.

Here's the template for the spacer.

 

Thanks for the pics DB..

Where can we get the blower motor? can we just buy one from an autopart store or is it a dealer item?

I would think(but what do I know) that using the factory OEM thick gauge wire to and from the high speed blower relay would provide the same voltage as wiring from the alternator no? I mean I guess adding a 30 amp relay would build a little more voltage in the coil but... Not sure I really want to run extra wire and relays, I suppose I could hide them but.. I might try it with the factory wiring first then if its not any stronger, re-wire it. I just can't see having two relays on the same circuit., maybe it could help though.

Wasn't someone making the spacers a while back and selling them or was that for something else?

 

The C4 fan is available new in stores very cheap gut they don't come with the blades I don't think. Check on that. I bought one on Ebay for $10. Almost new.

The wiring that normally runs that fan goes through the harness. By the time it gets to the motor it's running right around 12 volts. Show it 14+ and it'll really spin up.

It's very easy to hide the relay back under that fender, and conceal that wiring in with the factory harness.

 

Yeah I just found a blower motor W/ fan at Autozone for $35. Its for a 96 C4. I guess the year doesn't matter right?

OK I will check the voltage at the blower now with the car running, if its not at least 13.5, I will run another thick wire to it and stick a 30 amp relay in there.

I think the last time I checked my out put on the alternator it was only like 13.5 or so...no where in the 14s I know.

That template you posted, that the actual size? LIKE I can print it and cut it out..?? LOL

I bet cutting that out of cutting board is a PITA....LOL

 

Yeah, depending on the image program...just resize it and print it until it's correct.

From a cutting board, do .5" layers, and do them one at a time. Use a medium tooth blade, and a variable speed jig saw and remember to go slow with the blade so it doesn't melt the board and stick.

 

OK, when doing the blower motor, which is a good change.....you first need measure the voltage drop on the ground side AND supply side, from engine block to fan frame.....and from alt out to + feed on blower, this all on high speed, obviously.....

I found my ground lead dropped a whole VOLT and the other + power lead was about 1/2 volt....both changed out for OMG wire...about 8 ga.... stock relay....and went to the C4 motor/cage as described above I managed to use a 3/4 inch spacer, apparently some guys need more....

all I can say is to suck out the leaves from the pressure side of the evap coil....this best done with a small vac hose from a shop vac through the motor/fan hole....

I also sealed shut that pesky door up under the fender down the wiper well....and put it on permanent recirc by removing the inner door also, up under the pass kick panel....

 

Mr Vette, How do you get to the door in the fender/wiper well you speak of? what all do we have to take off to get to it? I have been looking all over for info on that thing and can't find CHIT on it. I will check the voltages and grounds at the fan.

Now when checking voltage at the fan, do we just check the wire that powers the fan while the engine is running or do we actually need to leave the wire hooked up, turn on the AC and the fan to HI and measure it with all the draw?

I mean its gonna have a lower voltage reading if its hooked up and the fan is running on high.

 

OK guys, did some voltage checking. At the alternator when warm I got 14.0-14.2 coming out. The hot into the hi speed relay is 13.92 or so. If I turn the fan on HI and check the volts coming out of the hi speed relay, I am only getting 11.2v out and 11.0-11.2 to the blower motor when its running. Now if I unplug the blower motor, but leave the AC on and the fan speed on high, I get 13.8v out of the relay and right at 13.8v to the end of the 12v hot that plugs into the blower motor.

So my conclusion is that I got 13.8 going to the blower motor when the motor is NOT running. If I check it with the blower running its only getting like 11.0 at the motor. Does this sound right? it seems like the blower is using almost 3v to run. I mean my blower blows pretty damn strong for an old one but....I am just curious if I put the C4 blower in it if it needs more power.

 

Keep in mind the C4 blower fan isn't really more powerful than the stock C3 fan. The difference comes in with the extended cage, and more highly pitched blades. The relay idea is just to get as much power as you can get to it. If the juice is coming from the alternator...it'll have all the power it needs.

 

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I agree, that tube is important, but in this case everything goes in the way it came out minus the old fan, taken by the new fan, and spaced out. I tested mine by trying it in the housing with no spacer. It maxed out at just under 1" in my '77 A/C box. I figure, guess, that a 1" spacer would put the back of the cage just out of contact range.

 

DB, I measured my volts at the alternator after it warmed it and it was 14.0-14.2, in that range at a 650 rpm idle. I measured the voltage at the relay at 14.0-14.2 so no loss through the harness up to the relay. I measured the volts out of the relay to the wire w/ the capacitor and it was 13.8 so it lost .2v going through the relay with the relay switched on(Hi speed on the fan turned on, fan disconnected). Then I measured the volts at the plug for the fan and its the same 13.8v. SOOOO from the alternator to the blower itself, I am only losing .2-.3v. Hardley worth worrying about. I am kind of concerned though that when the blower is hooked up and running on high, I am only getting 11.0v at the blower and 11.0v back at the output of the relay when the fan is on. I am not sure if the fan should be pulling that much voltage but..... F' it, its been like that 36yrs so.....

I am just gonna stick the new C4 blower in and use the same wiring and see what it does. I couldn't imagine going up .2-.4v making any noticeable difference.

 

You never know sometimes, it's car to car. when I did the same measuring I found almost a full 2 volt drop.

 

I'd cut that out with a router it will be a lot easier on you cuts that polywhatever like butter

 

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The age difference in cars is the difference then. My stock fan is almost an exact match to the C4 fan I bought. Very minor clocking differences at best, and I will have no problem adapting the tube.

The cutting boards I plan to use, which is also the way the guys before me did it, were .5" thick each. Cut two adapters from the cutting board, sandwich them together, and get the 1". I have never seen one that thick either. Improvisation. Gotta love it.

 

Yeah DB, I was going to use the 2- 1/2" cutting boards and glue them together also but I didn't realize the shape of the blowers are different? Will the screw holes even line up? or is it the same pattern only clocked differently? so my tube won't fit the same?

HMMM

This might be a PITA.

 

IT IS NOT On the Damn + feed through the relay, not on my '72 here or any other shark I have worked on.....the voltage drop is because they used too thin a wire on the GROUND side of the motor frame to the engnine block....this wire is like a 12 ga or so from the starter/bellhousing area, with a 3/8 diameter loop on it....and it's black fairly thin wire....going up to a junction feeding the relay ground for the coil, the wiper motor ground at frame...plugs into the driver's lower front, AND the blower motor frame....

keep one thing in mind....the damn blower motors for all the GM cars of the ear were nearly identical...A-B body F body, G body, even the Vette.....NOW the other cars are steel, and as such had NO ground voltage drop....typically....SO the fan motor had fulll voltage throug the exact same circuits the Vette has to run the positive side of things.....

so having a full load of only 11 volts across the fan motor with everything running full bore...tell ME, that your ground wire is too thin....

BTDT....beleive me when I say....it wasn't untill year or so later I upgraded the motor/blower assy with C4 stuff....

the stock motor/blower seemed to nearly double it' output...no lie....

gotta unnersand elek tronics....lek trick als to figger out why....

don't matter for this discussion....

At any rate, from what you said above....the GROUND wire needs be much larger, and while you at it, redoing the harness....put the damn ground tab/loop up top where it belongs so not confused to some mekanik when changing starters...another problem with that wire loop location.....