The same voltage going to the motor is not the primary factor for fan POWER. That would be amperage. And different motors are designed for different loads. Higher load motors draw more current (at the same voltage). So, "NO", all 12 volt motors don't run at the same RPM and do not provide the same fan output.

Also, new 'repop' motors come in different configurations. The cheapo versions have about 1/2 the motor windings that the original motors had...and they are relatively inexpensive when compared with a 'direct' replacement. The auto store folks won't tell you that. But, you can ask if they have a "heavy duty" replacement and compare the two units. They will be vastly different in magnet/winding design.

For the trouble you will be going to for making this change, buy a high quality upgraded motor, if you buy one at the auto parts store.

 

Ok so im a bit confused on this thread. I have the same problem on my 71. It sounds like the best thing to do is to upgrade the ground wire first and test it out. If that still doesnt work, then upgrade to a heavy duty motor assembly from a later year. Is this correct? If so where exactly is the ground wire routed?

- Ron

 

i upgrade my ground wire about 2 weeks ago on my '72, it was like having an extra speed on the switch
just made a small "Y" jumper lead that i placed in between the fan and the original lead

female socket ===== male spade
||
||
heavier wire with ring terminal

just reached in under the fender and removed the ground lead from the fan
placed my new jumper in, reconnected the original ground wire to the short lead

then the extra heavier lead i connected to the wiper actuator mount
had the fan on without the extra wire, then earthed the new wire and you could hear the difference
just tucked it in amongst the vacuum hoses to the relay

 

Anyone know where to order a C4 squirrel cage to fit ? And will any C4 squirrel cage fit?

 

would like to see some picts of the ground wire upgrade if anyone has some.

 

the small "Y" lead i made with heavier cable


tight squeeze to get into to see it connected


tucked in with the vacuum hoses and connected to the wiper actuator

 

OK, so let me tell you my adventure with this upgrade, or maybe I should call it my misadventure. Weather forcast for Sat was great with no rain. Started the project around 0930. Removed all the bolts from the ac compressor, took the belt off and moved the comp out of the way. Removed the overflow tank which was never going to come out without removing the ac compressor. That took about an hour, not bad so far. I had a 4 seasons C4 motor and bird cage. I had already made the spacer and glued it to the motor to make it easier to install. I also used a light glue to hold the screws in place so I didnt lose any wiggling the motor around trying to get it in. I couldnt get any of the screws to line up with the holes. I could get the top 1 or 2 but could never get all 5 to line up properly. Screwed around with that forever. Wound up breaking one of the female receptacles where the screw goes in off the housing,,,, arrrrghhhh break out the jb weld. An hour later all is fixed and hard enough to work with. Finally decided to pull out and re=install the original motor just to see the proper line up. More wasted time. Tried the C4 motor again and still couldnt get the holes to line up. Take the C4 out, more wasted time. Decided to take the bird cage off and just use the C4 cage with the old motor. Took the bird cage off the C4 and off the C3, installed the C4 on the C3 motor then I dropped the nut that holds the cage on. Of course It fell in the grass and of course I couldnt find it. And of course the nut from the other motor doesnt fit the other motor,, arrgghjhjj! Go inside and luckily find the same size nut from my work cabinet. Now Im cooking with gas,,,, Pull the 3/4 plywood spacer off the C4 motor and glue it to the C3, wait an hour for the glue to dry. More wasted time,,,, Finally install the old motor, new bird cage, spacer etc installed. Plug it all in and it doesnt work. Arrrgggghhhhhjh!!!! Somehow I blew the fuse for the blower and we know where the fuse is located, all the way at the top of the fuse block. So end result was old motor, new bird cage , but I did upgrade the ground wire with a heavier guage connencted down on the frame where some fuel line/return line were bolted. Seems to blow harder, the first 90 deg day will tell. End of day at 1430 hours, will never try this again,,,, no wonder its been on my list for 3 years and never attempted,,,,,, There was not enough beer for a day like this.

 

Try taking the WHOLE A/C box out! That's what I attemted a few weeks ago. I didn't want to go the spacer route. So I took the box out, cut it in half, fiberglassed it bigger, then replaced the fan with the bigger cage. In order to take the box out without taking the motor out = remove valve cover, remove exhaust manifold, move A/C comp. remove overflow tank. Then while it was apart I replaced all seals and took out the heater core. Took me about a week to take apart and put back together.! Hope it all works out for you. For me, It did'nt. I need a new condensor. I will attempt an electric fan on the old one next week to see if that helps any.

 

I still can't see how that thicker ground wire (looks ~12 gauge) would improve the speed of the fan motor. Power going in is the same. What am I missing?

And why that wiper supplementary ground? Will any nearby ground (e.g. heater core firewall stud) do the job?

 

I don't know what to tell ya but to just try it yourself and see. It deff. improves the speed.

 

I prefer not to try it until I understand what electrical principles are behind the motor speed-up using a double ground on a stock system and what long-term consequences to motor life might be. There are always trade-offs when second-guessing GM engineers.

But the thread has been interesting and people may be on to something.

 

No I did not use a double ground. I replaced the ground wire with a larger grade. Have had it on now for 6-7 months.

 

My mistake for which I apologize. I was looking at riverracer's pic where he is grounded into the normal wiring harness via a 16-gauge (?) and to a frame ground (wiper door mechanism) via a 12-gauge (?). He used a "Y" setup.

Have you just run a 12-gauge from the fan motor to a frame ground and left the wiring harness ground vacant?

 

Thats what I did.

 

Got to give the new bird cage a try yesterday with the really hot weather. Must say it made a noticeable difference in blower speed.

 

What did everyone use to 1) seal the spacer (if made of wood) to the box and the fan and 2) since I will be using two pieces of wood, did others who did glue them together, then cut them out, and what glue did you use if you did. I am thinking it's gonna be a bit hot down there.... Thanks. I am anxious to get this put together and see the increase in air movement. I thought I must have had a load of leaves/debris in mine, as I could hear the fan flicking on something so took if off, everything thing looks pretty clean; it was the birdcage rubbing on the fan housing. I will be replacing the fan with one for a '92.

 

I used black silicone on both sides of the wood spacer.

 

Great tip, I shall do that with mine. Thanks

 

 

auto zone.