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90-96 Fans in a C3

K

KenSny

Guest
My nephew who works in a "recycling" yard says he has a 94 Corvette (he says 90-96 are the same) dual fan and shroud assy that looks good and the motors both work and if I want it I can have it (no relays or wiring harness).

I was going to put on a single 16" fan or dual 12" fans without a shroud, by fabricating my own mounting brackets and such. But this seems like too good a deal to pass up.

Question: Has anyone done this? He says the left fan sits out a little further than the right fan - the shroud is raised so that the fan sits a little further back that the right fan. I would be interested in knowing how much shroud modification is necessary to fit around the a-arms and such - if it fits at all.
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
It has been done. I think it is a good idea. However, I think you are in for quite a bit of mods to make it fit right.
 
K

KenSny

Guest
Probably, but the price is right - $0 vs $250 for a SPAL. At the very least I could pull the fans and use them side-by-side without a shroud. I know they pull a lot of air and they are GM parts (BTW: the motors currently go for over $100 ea.). Since I'm going to have the radiator, shroud, core support out in a month or so, I can lay everything out on the bench and make up brackets and such without breaking my back leaning over the fender.
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Ken,

The only real problem is the actuall fans are less than 12" in diameter. They depend on the shroud to efficiently direct the air out only the fan holes.


If you end up with open areas outside of the fan blades, it may not cool it good enough.

Just a thought.

Chris
 
K

KenSny

Guest
Well, I'll get the fans and shroud when I see my nephew next weekend.

Someone on another forum pointed me at www.idavett.com where Hib Halverson had used the same fan assy on his "Big Block From Hell" car. The article talked about modifying the shroud and to see the pics, but could not find any pics there.

So it's going to be another fun trial-and-error project....

Now - Does anyone have a good schematic of how to wire up the dual fans so that one comes on with the A/C? I'm assuming I need 3 30a relays.
 
R

Roy M

Guest
Ken,
I recently installed dual 11" Spal fans. I bought them from Haywire, Inc. and they pre-wired to the relays for me so it was fairly simple for me to hook them up. The only thing that I see that you need to also locate is a temperature sensor, probably get one from that model vette that the fans came out of. Below is the way my fans are wired up.
WIRE COLORS

Black with Red Stripe -------- Power to Fans

Black----------------------------- Grounds

Orange--------------------------- To Air Conditioner

Pink------------------------------ To Ignition Hot [only when key is on]

Red w/White Stripe------------ Temperature Switch

Red------------------------------- Power Hot

The three relays are fastened together. What I call No. 1 is on left. It has the main power going to it.

No. 1 RELAY

85 - To Ignition and to 85 on second [middle ] relay. [passenger side]
30 - Power to Fan
86 - To Temperature Switch and to 86 on second [middle] relay
87 - Battery Power [alternator] and to 87 on second [middle] relay

No. 2 RELAY

85 - From 85 on first
relay
87 - From 87 on first
relay
86 - From 86 on first
relay and to 30 on third
relay
30 - Power to Fan

No 3 RELAY

85 - Jumper to 87 on same relay
87 - Jumper from 85 on same relay and to ground
30 - Jumper from 86 on second [middle] relay
86 - To Air Conditioner


Hope this helps. If I can be of more assistance, let me know.​
 
K

KenSny

Guest
Thanks Roy, it does help even though I'll probably get the relays from Summit. I should be able to put a wiring diagram together from your info and go from there.

The sensor from a '90s vette won't work because the fans are basically ECM controlled and they run hotter than our C3s. I can get a sensor to fit in the passenger side head that will come on at 200 deg and go off at 185 deg (my thermostat is 180) so that should work out great.


BTW: You said you got the wiring kit from Haywire and they prewired everything for you. Can you tell me what you paid for the wiring?
 
R

Roy M

Guest
Ken,
The cost of the three relays and wiring ran $45.00. I thought it was a good deal since I was getting the fans from them, they prewired the relays and labeled all the wires so it was a no brainer to hook up.
Also, I have been told by several people that it might not be a good idea to mount the sensor in one of the heads due to possibly picking up external heat from headers or the exhaust manifold. You have two other alternatives, either in the intake manifold or in the thermostat housing. I placed mine in the thermostat housing. I picked up the power from the alternator but may change to starter solenoid. I mounted the three relays on the firewall just left of the wiper motor. I just recently installed a remote solenoid, again on the firewall near the heater so it would now be a easy hookup and hopefully this would not affect the alternator in any way as you would be pulling juice straight from the battery when the fans are energised.
 
K

KenSny

Guest
Thanks, I'll give them a call. I can't see how it would hurt the sensor to be mounted in the head. The bulb is what is in the coolent path. If the heat from the exhaust manifolds was a problem then the temp gauge sensor wouldn't work either..... basically the same thing.
 
R

Roy M

Guest
Ken,
That is what I thought also but I called Spal and asked to speak to the tech department when I was mounting the fans. Also asked several other questions and they recommended not to install the sensor in the head because it could give a false reading, just what I was told.
 
K

KenSny

Guest
Thanks, I'll have to double-check that with whoever I get the sensor from.

BTW: on your post above, relay #2 the second 87 should be 86 right? Also where did you connect to the A/C I was told it should go to the "clutch coil + terminal", need to figure out where that is located....
 
R

Roy M

Guest
Ken,
You are right about the relay, it was a typo.
As far as the sensor, you can also get them from Haywire, they have one with 3/8" threads that comes on at 195 degrees and goes off at 175. Also they have one with 1/2" threads that comes on at 185 and goes off at 165. I had to go with the larger to fit in the thermostat housing. The 3/8" will fit in the head or intake, at least it would on my edelbroch intake. They are something like $17.00 each.
You should have a connector with two wires running to the air conditioner compressor, a green wire and a black wire, the black is ground and the green is power [at least it is on my 79], I just spliced into the green wire and everything was good.
Try this site if you haven't already, www.haywireinc.com
 
B

Bullitt

Guest
I'm glad you guys are picking up on this subject, as I will venture into it soon. I'm sure you cannot use the fans off a Pontiac, but some shrouds were made by them with two fan openings. I'm going to look into perhaps just finding some heavy plastic shroud material that I can cut up myself. I could mount the fans in a better way, but if Hib fianally get the pics worked out on the BBFH, we could aviod this. I saw a fan kit at the local hardware store for another type of electric fans, so I'll see if that can work. Roy, did you use the thermo housing that already has the sensor opening? I have one sitting in my garage right now, so I'd use it if possible. What temp are your fans kicking in at? Thanks guys for anymore answers. :) --Bullitt
 
K

KenSny

Guest
I was told that the '95 Camaro and Trans-Am (and what other 90's for these cars, I don't know) has a dual fan setup similar to the 90-96 Corvette. These are pretty heavy duty fan motors from what I've read.

As for the sensor, I was told by a tech at Be-Cool radiators that the fans should turn off about 5 deg higher than your thermostat, and come on at around 200-210 deg. From other things I've read this is about the optimum operating temperature for your engine.

From other comments I've seen, the shroud restricts some air flow thru the radiator with the fans off at freeway speeds and may cause the car to run a bit warmer than if you used the water pump driven fan. So some hole drilling in the shroud, as Hib stated, may be a worthwhile effort. I'd really like to see those pics.....
 
R

Roy M

Guest
Bullit,
Yes, you can use the thermostat housing that is stock on the c-3. The one with 1/2" threads for the vacuum sensor or whatever that thing was called. If you get this sensor from Haywire, it will kick on at 185 and off at 165. It is not adjustable.
If you haven't gotten any fans yet, you might check on late model Firebirds or Camaros. Seems like I heard someone say that the fans were very similar to the ones used on the C-4 Vettes. If you can find something like this, you would not have to fabricate any type of shroud, maybe just modify a bit to clear the A-arm. I know when I mounted the Spal fans, there was very little clearence, approximately 1/2" but that was enough. Also, I have heard [heresay, no experience] that some of these fans have a short life but the parts for them should be readily available from a GM dealer.
If I can be of anymore help, please advise.
 
B

Bullitt

Guest
Having owned a L98 dual fan set-up in a GTA Trans Am, I only experienced relay failure. The fans worked excellent, but the motor went a bit hot, I think for emission reasons. I owned the car for four years and drove it pretty hard with a ending mileage of 155,000 miles. Someone else was saying in a similar post a month back, that they had trouble fitting in the F-body shroud. So when I mentioned Pontiacs, I was also thinking about the Grand Prix shroud. I'm not sure if the fans are the same in the GP, hence my reason for apprehension.

If I'm correct, the C4 shroud sells for aroung $60-70. It might just be worth it to see if it would fit better and if it doesn't, just return it. I have a fan from a late-model Corvette sitting in my garage, from all the parts I've collected over the years. There was another set-up in mid-'80s F-body designs that did not use a surround shroud. They had top and lower brackets and the fan support. So experimentation is in order, I guess. I have more pressing matters first though, in my '71. Like Tom, I have to do something about my pop-ups. I think it's time to sell them. Good luck guys and hopefully, I won't fall too far behind. :) --Bullitt
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Okay, here we go.

The best way to do this is to get the complete relay/sensor kit as sold by Pep Boys made by Hayden.

Anyway, it is much neater and cleaner than any of the suggestions here and about $30. It comes with a temp probe sensor that goes into the radiator. Before you think this is cheap, I have used them on a dozen or so vehicles with zero failures. It will cut on at 180 and off at 170. You can choose to use the coil signal wire as either ground or 12+. The best way to do it is to run ignition on 12+ through the radiator sensor and you also tie in the a/c clutch 12+ to this same lead. That way when the a/c is on it kicks the relay and fans, and or any time the sensor is 180 or above. It is neat and clean, only one relay, and can be installed in a short amount of time.

They sell another one for around $40 that has an adjustable temp sensor if you really want to dial it in.
 
K

KenSny

Guest
Update:

Got to look at the fans and shroud today. These are side-by-side GM 15" fans (real monsters - if I still had the Camaro these would be perfect), and the shroud is a lot wider (by about 5") than my radiator. Not at all like the pictures in the 94 service manuals so I guess they are the wrong units, or something.... Anyway, I'll be letting him take them back to the yard.

Need to rethink this now.

I was looking at the stock shroud itself, and it looks like I could mount a 16" 2900cfm Perma-Cool fan to the radiator since the opening is 18" and retain the stock shroud, or at least the main section and remove the front extension piece (the part that fit over the stock fan blades).

I also talked to Perma-cool and they suggested that:
(1) Try to have the fans cover 70% of the core if you are not going to use a shroud.
(2) I need at least 3000cfm for my application (A/C and 330hp).
(3) I could mount 2 of their 12" fans, each has a 1650cfm rating, side-by-side on the radiator for a total of 3300cfm. BTW: they do not recommend fabricating a shroud for these.

Does that make sense that you can double the cfm like that? Wouldn't the radiator still be seeing 1650cfm being pulled thru at any given spot? Or am I looking at this wrong? I notice that SPAL does that too, they have 2 11" fans for a total rating of 2780cfm whereas each fan by itself is half that.
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Sounds right to me. It is the CFM per surface area, and with two 12" fans you get that per surface area etc.

At this point they are the experts and know their product the best. No doubt the dual fan will give you the most air flow, more is better, and with no shroud I guess the air can pass through at highway speeds.

Keep us up to date. Bummer on the salvage yard units.
 

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