REELAV8R

Well I finally got around to changing the cabin blower fan over to a C4 blower in my 77 L-48. Actually what forced my hand was the failure of the original fan. The rubber grommet for the positive terminal and insulation on the original fan had turned to a gooey like substance and no longer prevented the fan from shorting to ground internally. So I figured since I'm gonna be in there why not change it out to a C4 fan and increase the airflow in the cabin.
I read several threads concerning this to get a heads up on what was needed to get the job done.
However nothing I read really prepared me for the trouble that the a/c system and all it's components were gong to cause me.
First of all to get to the fan motor the radiator overflow tank has to be removed. No problem right? three bolts in the wheel well. Took those out but could not remove the tank due to a/c compressor being in the way. So took the a/c compressor off it's mountings and moved it out of the way with hoses still attatched. Still can't get tank out. a/c compressor brackets in the way. Removed a/c compressor brackets. NOW the tank can come out. Now I can get to the blower motor. Removed all the screws (5) pulled the blower motor out of the hole but cannot get it out of the wheel well area due to high pressure line for a/c running near wheel well and the motor needs to come out between the inside of the wheel well and the high pressure a/c line.
Sooo I get the motor flipped onto it's back with squirrel cage facing up (all of this is under the fender area near fire wall out of sight unless you are leaning over and peering down into that area) and proceed to remove the single nut holding the squirrel cage on. I get the cage off the motor (it was stuck on pretty good and took some prying) and now am able to get the cage out separate from the motor. Then the motor can be manipulated onto it's side and with some finaggling and cursing can be shimmied between the high press a/c line and wheel well to be removed from the car.
The whole time down in the area where you are working the evaporator box is preventing a good line of sight to what you are doing and the low pressure a/c line is in the way of maneuvering the fan assembly around to remove the squirrel cage. Lighting is poor making things just that much more fun.
The 1 inch spacer that is needed to accomodate the additional length of the C4 fan cage I decided to make from 7/16 OSB and 3/16 pieces of plywood.
Originally I believed that the shape of the spacer needed to conform to the shape of the fan housing. However this is not necessary and it can simply be a round doughnut that is large enough on the inside to allow the fan to pass through and about 1 1/2 inches wide by the 1 inch thick for the longer fan.
I glue/screw laminated this all together and it came out 1 1/16 inches thick. Then I coted the "doughnut" with truck bed coating from a rattle can. Figured this would moisture proof the whole thing and prevent swelling of the wood.
The new C4 fan was purchased from Oreily's for $25. The fan for an 84 through 86 C4 is the same configuration electrically as the c3 fan. Made in china of course. (I repaired and kept the original fan in the event that I want to have original equip back some time in the future) The new fan is warrentied for life however so maybe ok. First thing I noticed when I bought the new one is that the fan cage was not round. I pointed this out to the guy there and he decided to spin it up on a battery. It worked so I took it.
Back home. When I tried to get the cooling tube for the motor into the hole on the new motor it (the hole) was too small. Not wanting to alter the oem cooling tube I decided to open up the hole in the new motor. Drilled the rivits out holding the motor together and seperated the rear section with the cooling hole and ground it out to accomodate the cooling tube then Pop rivited it back together.
Originally I was going to use longer screws and put them in through the fan housing through the "doughnut" and into the airbox. However I discovered that the new motor was clocked different than the oem motor putting the cooling hose in an unreachable position to connect to the cooling pipe on the car.
New plan. Now i recessed all the holes in the doughnut to allow the bolts holding it to the airbox to be flush with the surface of the doughnut that the fan housing would mate to. Then figured out where the fan motor needed to be clocked to and attatched the fan housing to the doughnut in the correct position using wood srcrews.
To do all of this I first put the doughnut on the airbox in the car then marked the position of the fan then took the doughnut off and predrilled the holes for the wood screws the mounted the doughnut on the fan housing making sure the squirrel cage would clear the inside diameter of the doughnut in the position it was in then taking the doughnut back off and attatching it to the airbox then attatching the fan motor to the doughnut.
Each time the motor needs to go in the car the squirrel cage must be off to get it in and out and the squirrel cage has to be installed with the motor under the fender in the "hole" your working in.
Finally success. All together. I attatch the electrical connections and fire it up runs good at all the speeds even high..... for about 30 seconds. Then that out of round fan bites me and it explodes. Fragments of the fan are all over in the air box and out of 21 missing/broken blades I am only able to retrieve 9. So the rest stay in the air box somewhere. Oreilly's gives me a new fan and this one is actually round.
Get the new one installed and finally NOW success.

Man what a PITA for what should have been a simple upgrade. Now that I've done it I could do it again and have an easier time of it but first time like many things is a learning experience.
Hope this write up helps someone else who may be considering this blower upgrade.
I would estimate the increase in flow to be about 50% better than it was. I can actually feel the air from the center vents in my normal sitting position whereas before I had to put my hand about 6 inches from the center vents to feel anything at all.
This helps to cool the car down much quicker on those hot days after it's been parked in the sun. Not to mention being black makes the car all that much hotter after sitting for a while.

SIXFOOTER

Don't you love it when a plan comes together?

REELAV8R

Love the A team quote.
I guess if making simple jobs hard were a profession I'd be paid very well.
Waaait a minute... don't engineers get paid well?

jcloving

Hard work yes, but worth the effort. I removed the lower splash shield when I did this work and it helped me access some of that stuff.

Now that it is done it will stay done. Enjoy.

REELAV8R

Do all the later model C3's have these splash shields? The entire underside of this car has some kind of undercoating on it and I have the feeling that some of these things are covered up so I can't see them.

jcloving

You would have to pull the rocker molding to get to two of the bolts. I think two are visible in the wheel well. It just gives you another access point to touch/handle the fan.

I did some work thru there when I put in the vir eliminator.

outrunm

I'm doing this job right now. I've got the blower motor dropped, but I will have to wait til tomorrow to jack the car up and try to squeeze it out from underneath by the starter. I did not allow myself enough room in the garage to get a jack under the passenger side. The garage backs up to my 5 year old's bedroom, so cranking up the car at 1030 at night is out of the question. Besides, my back is killing my from being bent over the car for the last few hours for a total of 5 nuts.

REELAV8R

Oh yeah, I didn't mention that this job will require good alcohol or your choice of pain killer if your over 30.

oldalaskaman

when you're over 60...both

outrunm

The alcohol worked. I kept messing with it and got it out. Now I wish I bought the motor when I was at CarQuest today. I will have to wait until tomorrow to put it back together, and I know I will be sore as Hell.

outrunm

Thats exactly what I did. Fun job with sidepipes. I was expecting to snap the panel because I simply removed the first 3 nuts on it and pulled it away.

ezobens

I'm looking to do this job over the winter but fortunately, I'll have the engine out and installing the evaporator box so I can fabricate the spacer ahead of time.
I'm curious as to why the spacer needs to be 1 1/16" thick? Other posts I've read indicate that you only need 3/4" spacer- Did I miss something somewhere?

I was planning on making the spacer out of aluminum but if it's over an inch thick, I may need to reconsider..

oldalaskaman

I've read the minimum is 3/4"

Katherinejjm

Just what I needed, thanks a lot.

'75

Best is to put the new motor and wheel into the hole and measure the gap to determine the spacer thickness. Mine was 3/4 and on a 78 I did it was also 3/4. Too thick a spacer and you will loose efficiency and too thin the blower wheel will rub or stop turning.

daanbc

On my 77, I was able to get the overflow and cage out. Granted it was a VERY tight squeeze. But is possible by twisting and turning. I also did the spacer thing, but later took it out along with the whole box. I then cut the box in half and fiberglassed it back together making it larger. Figuring if I had a bigger fan to move more air, I'd need more space for that air to be moved. My knuckles did get messed up a bit taking that Overflow tank out.

ezobens

I guess this brings up another question:
The C4 fan has a larger squirrel cage, which requires the use of a spacer (or modifying the housing), does the C4 motor also spin faster?

I guess I'm asking if you can install the C3 squirrel cage onto a C4 motor and avoid the whole spacer issue altogether?
If the C4 motor is more powerful (spins faster), you may still see some benefit, albeit not the full benefit as you would using the larger squirrel cage.

Has anyone compared the output of the two motors?
Elm

oldalaskaman

I have read that they spin about the same , but that the C4 cage is designed different and moves air better

'75

My understanding is that the motor speeds are the same, the added flow comes from the larger wheel. Increasing the size of the ground wire to help carry the amperage is also reported to increase the speed of both motors. Many times there is debris blocking part of the evaporator coil from years of accumulation.

ezobens

OK-
So if it's the same shaft diameter and mounting as the C3 motor, you could theoretically just buy a C4 cage and use the C3 original motor?
Guess I need to pull out both motors and do a little side by side comparison.
Thanks!
Elm