Haggisbash

Hi, I believe there is a better fan motor that will fit the c3 to give it a bit more oomph. Did it come out of a truck or was it a C4 fan does anyone know?

Amorget

C4 fan + spacer is a popular mod

Easy Mike

Yep...and uses the C3 blower motor.

Haggisbash

I have seen info regarding the output of the C4 fan being greater and it looks like the motor in my fan has died of old age so hopefully the C4 fan motor will fit, I know you have to put in a spacer to fit the C4 fan because it is longer.

Shark Racer

The motors perform the same; the modification is to use the fan cage off a C4. Because the motor is longer, you need a spacer so as to avoid hitting the inside of the heater box.

If you go with a C4 motor, you'll have to add some wiring to your list of things to do.

Roozstr

No wiring necessary if you use 83 or 84. Gm changed to a two wire in 85.
I bought mine from NAPA for $27

Shark Racer

Looks like the 84 Corvette blower motor comes up with a bunch of the same part numbers that I find for 78... sounds more like the 84 used a C3 blower motor to me.

Roozstr

OK
Here is a 84 blower motor on the right and an 87 on the left. Both are new from NAPA. There is no difference aside from the connector.

I will pull my 73 blower motor today and post the OE one next to the new ones in the morning.

Roozstr

Damn It only took 20 minutes to pull the blower motor so here is the pic.
84 on the left, 73 in the center and 87 on the right.
Looks like I'm going with the 84.

Shark Racer

Great pics, thanks for sharing.

I wasn't disagreeing with you, per say, just stating that it looks like they went to a new blower motor in 85 and continued using the same motor the C3s used in 84. Your pictures tell the same story, the 73 motor looks very much like the 84 motor, minus a couple years of dirt and grime.

The "84 motor" looks a lot like the new motor I put in my 78 a few weeks ago as well, coming off of a 78 SKU. So effectively, the 84s are using a "C3 motor" and the 85+ are using a "C4 motor".

Regardless, your pictures do the forum a great service.

I'm running that setup in mine, except as said I told the parts shop "78" for the motor. If you haven't got a cage already, looks like just getting an 84 setup w/wheel is the easiest "point and click" way to get done.

Curious how well it works for you. Mine is not that great; I suspect I need to do wiring mods. Many others have stated this when discussing the conversion; ground is not good enough to get full voltage and the next step after that is updating power wires.

Haggisbash

Blower started working again and then not and then yes. Seems I have a wiring issue. I jumpered straight from the back of the alternator to the blower and it runs but is noisier than it should be and I still think is should have more speed.

Street Rat

Try a bigger ground wire to a different location first. This alone made my blower motor blow faster. If that doesn't satisfy you then you can always do the motor/fan upgrade.

Roozstr

Physically the motors are identical. The only difference is where the steel mount is located.
Making the spacer out of black 3/4" UHMW plastic now. Will post pictures. I will trace a template when done if anyone is in need of it. Note: do not use the one on http://www.vettemod.com/. It does not fit. Trust me!

Haggisbash

Seems that later motors have a pipe to allow cooling air into the motor, this doesn't exist on the early ones. I have to wonder with the increase in fan size if the motor was made more powerful, it would be nice to know if they both draw the same amount of current, even that is not the be all and end all though as the later motor could also be more efficient.

Roozstr

If you notice in the pic with the three motors, the cooling tube is hooked up to the 73 motor. The 84 motor has a plastic plug in the same place that tube goes to. The 87 motor has a hole in the opposite side which would require more plumbing. Again another reason why I went with the 84 motor.

Roozstr

OK here is the spacer I made. Took a while to make a template and Cut the plastic. Glad I went with the plastic it is much cleaner and durable than plywood. If anyone would like a copy I have it on a PDF file. PM me your email address and I will send it to you.

Roozstr

Got the blower motor in today. I can finally feel air blowing out my registers. I put a bore scope in the evaporator to see if there was any debris in it. Clean as a whistle. Blows about twice what the OE blower motor did. This vehicle has only 18,000 miles on it so I am sure the blower wasn't worn out. Made a ground wire that goes from the bottom two mounting screws to the lower mount bolt on the A/C compressor. That is the orange wire in the pic. I am a happy camper. Definitely worth it.

Roozstr

Yes definitely do what street rat said. Need a good ground first.

I think you have a 70? I have a 73 but I think they are pretty close. Is it high blow only that does not work or all speeds? If high only check the inline fuse near the horn relay. If all but high check blue, yellow and green at the resistor. Should have varying voltages depending on blower speed. . If all speeds it will probably be something inside like the blower switch, master switch or connections to any of those. Does it have a/c?

Sorry if I hijacked your thread but I was in the middle of doing what you were asking about and thought I would share.

Dave

Haggisbash

Hi Roozstr, all the speeds work when its working but it has no real blow if you know what I mean. Its like an old vacuum cleaner that has lost its suck, the motor still goes and all but no real grunt. I am going to pull the whole heater assy to pieces and check every thing "while I'm at it". Looks like the only way to find out is by substitution so I will order another motor as you have before I pull it all to bits. I already have a heavier ground wire fitted but it made no difference.

Roozstr

If you shine a light in the screen area in the well for the wipers, you can see the blower motor wheel. Have someone work the speeds and see if the cage is spinning fast. The new one I just put in is a blur at high speeds.