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There is a myriad of conflicting information on Mark VIII fans. Nobody seems to have it all right. I have read through 2 dozen threads and have called a couple shops that sell these trying to figure this out. Here are the results of my research -

I know for a fact that there are three part numbers for the Mark VIII fans as follows:
93-96 F3LY 8C607 A 1100 on low and 1850 on high RF123 Y=lincoln/mercuy
97's F7LZ 8C607 AB 1800 on low and 2225 on high RF56 Z=ford
98's F8LZ 8C607 AA 1800 on low and 2225 on high RF64 Z=ford

All these fans are single speed PWM controlled by the car. I believe the middle wires on ALL of these are either tied together at the motor; or don’t exist (It has been reported that 97 and 98 have only two wires in their pigtail).

There are several stock pigtails that have been reported as taken from Mark VIIIs:
2 black 1 green (all same gauge, blacks tied together at motor)
2 black 1 blue (all same gauge, blacks tied together at motor)
1 black 1 brown or orange 1 Blue (different gauges for the positives)
1 black 1 Org/Blk - Low 1 Blue - High (different gauges for the positives)
1 Black 1 BRN/Org - Low 1 Brn/Yellow - High (different gauges for the positives)


I don't believe that Ford was putting different harnesses in the engine bays within a model year and I doubt it changed between 93-96 particularly the ones that have differnt gauge wires. If this were true I have yet to see a wiring diagram that proves it.

Fan/Replacement_Motor/Vehicle Data:

RF123 75717 Mark VIII 93-96 (1-speed 18" ?)

RF24 75715 T-bird LX 94-97 (2-speed 18" ?)
Cougar XR-7 94-97
(maybe others)

RF125 other Taurus GL 90-95 (2-speed 16" ?)
Taurus L 91-92
Taurus LX 90-95
Taurus SE 95
Continental 90
Continental Executive 91-94
Continental Signature 90-94
Sable 90-95
(maybe others)

I think the confusion lies with the RF24, It has the unique Mark VIII fan blades and shroud but a different motor. This is a true 2 speed motor; presumably these cars don’t have PWM controllers and just use two speeds whereas Mark VIII can achieve multiple speeds by PWM. I think this fan is mistakenly referred to as a MarkVIII fan. This helps explains all the different wire colors and sizes that are reported as being a Mark VIII pigtail. The shroud and fan blades looks identical but the middle terminal on the RF24 motor is not a "dummy". The plastic plug at the motor is black instead of white and it does not have the “inspection cover” near the plug. I suspect RF24s were assembled in Canada and RF123s were assembled in Mexico which accounts for that misconception. Presumably, high speed on the RF24 motor is not as good as the M8 motor wired straight to battery but I have read threads that say high on a 2speed is better than the single.

*** UPDATE *** I pulled the fan blades off my 93 1-speed and the motor is #F3LU - 8K621 - AA and is stamped CANADA. It crosses to a #75717, so that blows up this 2 speeds come from Canada story. I have also learned that the two-speed motor is #F4SH-8K621-AA which crosses to a 75715 *** UPDATE ***

I have read threads where the author swears that he pulled the fan himself from a 93-96 Mark VIII and it was a black plug 2speed. IF this is true and that is a big IF; I suspect that Ford, in a pinch, would sustitute an RF24 if they were out of stock on RF123s for the 93-96 model. Theoretically the VCRM wouldn't care which was there since both fans have 2 wires that are positive and one ground. I bet due to the way the VCRM pulses based on conditions (engine temp, A/C, etc); the net cooling effect is the same whether both positives are one speed or two. The reverse however is not true. You can't put an RF123 in a T-bird/Cougar, although the fan blade and shroud are the same. Their relay system expects 2 different speeds depending on wich lead is energized. You would be on high all the time which is not desirable due to the current draw and startup spike.

As for the notorious "Taurus fans"; the RF24 and RF125 are both 2 speed motors but one drives an 18” fan (RF24) and the other drives a 16” fan with a curved blade and differnt shroud (RF125). Neither on high is as powerful or pulls more air than any of the three Mark VIII fans (RF123, RF56, RF64). On a side note, it appears that regardless of whether you have a 1 or 2 speed; any fan having 12v on both positive wires at the same time is not good. It makes high speed slower on a 2-speed and can affect the life of the one speed.

There is a pdf on the net that does an airflow and current comparison of "Mark VIII 2-speed" and a couple Spal fans. In the second post the guy admits that he doesn't know what the part number is of the fan he tested. He just said it was one of the "big ones from a Mark8". I think he had an RF24. This is the original thread it was posted in:

http://forums.corvetteforum.com/c3-tech-performance/1816636-markviii-vs-spal-duals.html


I believe all my data is correct. Let me know if I am wrong on any of this that you are SURE about. Also, I have a couple mysteries I am trying to get confirmation on:

1) Is the RF24 (T-bird/Cougar) on high really not as good as RF123 (M8)? Did maybe the person who tested this have both positive terminals connected on the RF24?
2) I believe the RF56 and RF64 spin faster but with a different blade design (presumably to make it quieter). Do they move more air than the RF123? I have read opposite reports on this.
3) What is the difference between an RF56 (1997) and an RF64 (1998)?
4) I bought a ’93 Mark VIII fan from a local yard. It has a white plug but is missing the “inspection cover” near the plug. Attached is a picture from a thread I read pointing out how to spot a 1-speed vs a 2-speed and a picture of the one I bought. Could the inspection cover be for an RF56/64? Maybe a slight redesign of the unit back when they were making the 93-96?



 

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I beg to differ the 97 98 mark 8 fans are over 4000 cfms, contact Brian baskin at dccontrol he has tested them neat 4500 cfms and he told me he just checked the 2010 f150 dual fans over 6000 cfms
 

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I bought a "Mark VIII" fan two years ago for my LS3 280Z at the recommendation of a friend and he wired up two 40 or 50 amp relays to run it at full speed. Last year I took it to a shop that does wiring to hook up my HID headlights. They decided to consolidate the ballast wiring on the passenger side and hook up one 40-amp relay into one black box to clean it up. This ran for a little while, say 1200 miles or so. The car overheated on my way back from Dallas back in May and the radiator burst out at the seams. I took it back to the shop and they noticed the 40-amp relay had some signs of melting and that may have contributed to overheating. They put in a Painless 70-amp variable speed relay to run the fan at low and high speeds based on temp, A/C on, etc. Well, I picked up the car to cruise it around and I was doing OK for about two straight hours, and then that relay caught on fire Saturday night. Good thing I was near a parking spot when the smoke started billowing and I had about a gallon of water with me to help put it out. 20 feet from the parking slot and the fuel pump went out too and the motor cut out.

Dramatic story aside, I am very interested to know what's going on and how the heck the damn thing is supposed to be wired up...safely. I am hoping that info will come out in this topic. Subscribed!
 

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I bought a "Mark VIII" fan two years ago for my LS3 280Z at the recommendation of a friend and he wired up two 40 or 50 amp relays to run it at full speed. Last year I took it to a shop that does wiring to hook up my HID headlights. They decided to consolidate the ballast wiring on the passenger side and hook up one 40-amp relay into one black box to clean it up. This ran for a little while, say 1200 miles or so. The car overheated on my way back from Dallas back in May and the radiator burst out at the seams. I took it back to the shop and they noticed the 40-amp relay had some signs of melting and that may have contributed to overheating. They put in a Painless 70-amp variable speed relay to run the fan at low and high speeds based on temp, A/C on, etc. Well, I picked up the car to cruise it around and I was doing OK for about two straight hours, and then that relay caught on fire Saturday night. Good thing I was near a parking spot when the smoke started billowing and I had about a gallon of water with me to help put it out. 20 feet from the parking slot and the fuel pump went out too and the motor cut out.

Dramatic story aside, I am very interested to know what's going on and how the heck the damn thing is supposed to be wired up...safely. I am hoping that info will come out in this topic. Subscribed!
Why not contact Brian baskin at dccontrol? Not cheap but the fk-85p is more that enough to handle the task.
 

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I am using a Mark 8 fan with a DCC controller from Brian, and it kicks butt!. I drive it on the street every weekend, and at the strip 3-4 times a year, and never a problem. I drive it on club cruises, parades, and road trips, and it does great. I drove it from Tn up to Louisville Ky last month in the mid 90s, and it never went over 180.

Here is a few pics of it.
http://members.tccoa.com/392bird/dcc.htm

The supply of new Mark 8 fans has just about dried up, so Brian is working on finding some thing that will work as well, in as compact package.
 

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I am using a Mark 8 fan with a DCC controller from Brian, and it kicks butt!. I drive it on the street every weekend, and at the strip 3-4 times a year, and never a problem. I drive it on club cruises, parades, and road trips, and it does great. I drove it from Tn up to Louisville Ky last month in the mid 90s, and it never went over 180.

Here is a few pics of it.
http://members.tccoa.com/392bird/dcc.htm

The supply of new Mark 8 fans has just about dried up, so Brian is working on finding some thing that will work as well, in as compact package.
You guys want some fresh-from-the-boneyard Mark VIII fans? I was in a yard with four of them (the fifth Mark VIII ran into something hard enough to shove the radiator into the water pump, and blow both air bags. Le sigh.)

RwP
 

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Mark VIII E-Fan Wiring..

One other option without running a Fan Controller is using a Solenoid and Toggle switch setup..
You can get a Toggle switch for a couple bucks, and a nice 200 Amp Continous Duty(Echlin ST34) Solenoid from Napa for $35..
This solenoid will handle any E-Fan you can throw at it..Here's a diagram of how to wire it up..
Make sure the wire going from the Battery to Solenoid is 8 gauge,and your Grounds too..
Mark VIII E-Fan Relay Diagram.jpg

If you're not running at least an 80 Amp (Continuous Duty) Relay/Solenoid....Or a DCC Controller..You're going to keep burning Relay's up..
The Mark VIII fan pulls A Lot of Amps..


I'm running a setup similiar to the one in the diagram...
With the 200 Amp Continous Duty(Echlin ST34) Solenoid from Napa and Mark VIII E-Fan..

Since I use the Mark VIII E-Fan on high continuously in conjunction with my 200 Amp Continous Duty(Echlin ST34) Solenoid from Napa..
I ditched the Mark VIII E-fan factory wiring harness..
The high amps that the Mark VIII E-Fan pulls will eventually melt the Mark VIII E-Fan factory wiring harness..

I'm using Insulated Female Quick Disconnect's like these in the place of the Mark VIII E-Fan factory wiring harness :
Insulated Female Quick Disconnect.jpg


With the Insulated Female Quick Disconnect's you don't have to worry about getting stuck on the side of the road..
Because your Mark VIII E-Fan factory wiring harness melted on you.. :(


This should clear up some confusion on how to wire the Mark VIII E-Fan up..


:thumbsup:




Rayo..
 

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I beg to differ the 97 98 mark 8 fans are over 4000 cfms, contact Brian baskin at dccontrol he has tested them neat 4500 cfms and he told me he just checked the 2010 f150 dual fans over 6000 cfms
you sayin' those could fit? :D :confused: :) :tongue:
 

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Dccontrol stuff rocks got one on the 86 just put the 85 controller on the truck and Brian baskin said the 85 will run 2 mark 8 fans
 

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I beg to differ the 97 98 mark 8 fans are over 4000 cfms, contact Brian baskin at dccontrol he has tested them neat 4500 cfms and he told me he just checked the 2010 f150 dual fans over 6000 cfms
the numbers he posted are fan RPMs, not CFM.
 

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One other option without running a Fan Controller is using a Solenoid and Toggle switch setup..

If you're not running at least an 80 Amp (Continuous Duty) Relay/Solenoid....Or a DCC Controller..You're going to keep burning Relay's up...The Mark VIII fan pulls A Lot of Amps..
On my '93 Mark VIII, I rigged a cooling fan bypass switch like that using a continuous duty DC charging solenoid from an electric fork lift. 40A cube relays would not stand up to the task.
 

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Discussion Starter #12
There are all kinds of wiring instruction threads on the net about 1 speed and 2 speed fans.

Does anybody have any information that confilcts with what I have reported that you, yourself, are SURE of; not heresay or quoting other threads.

Can anybody answer my questions at the bottom of the original post definatively? I'm not buying any cfm numbers for any of these fans as the restriction used affects the number and free flow numbers don't tell you much. Maybe some real world back to back tests on a motor or something?

It is a fact that the 97-98 spin faster but that doesn't mean they work better. I am prestty sure the fan blade is different and I am guessing that had to do with noise. To get them to cool as well as the RF123s they had to turn them up. An interesting thougt might be what happens if you put a 97 or 98 motor on a 93-96 blade/shroud. The result might be the best cooling but also terribly noisy fan. But it could also just be more noisy and flow the same or less. Fan blade shape has a lot to do with how this works and you reach a point where spinning faster works against you.
 

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Discussion Starter #15
Any pics? I didn't there was ANY difference in the blade or shroud, just the motors
I have read multiple reports that the blades are different; can't say for sure about the shroud. Unfortuneately, I have never had one in my hands.
 

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I have read multiple reports that the blades are different; can't say for sure about the shroud. Unfortuneately, I have never had one in my hands.
I swapped my TBird fan for a Mark VIII fan. The blades do NOT mount the same on the motor, thus, they are different. I had to rig mine up because my motor burned up on the Mark VIII and a Bird motor fits in the frame, but the blade itself mounts differently.

Anyways, so even though the shroud looked identical (I think the mount points were different), the blades were very similar design, size, and shape, everything was slightly different.
 

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I swapped my TBird fan for a Mark VIII fan. The blades do NOT mount the same on the motor, thus, they are different. I had to rig mine up because my motor burned up on the Mark VIII and a Bird motor fits in the frame, but the blade itself mounts differently.

Anyways, so even though the shroud looked identical (I think the mount points were different), the blades were very similar design, size, and shape, everything was slightly different.
This?



If so the one on the left is NOT an original MN12 blade or motor. It looks like it came from a Taurus or something.
 

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Discussion Starter #18
I swapped my TBird fan for a Mark VIII fan. The blades do NOT mount the same on the motor, thus, they are different. I had to rig mine up because my motor burned up on the Mark VIII and a Bird motor fits in the frame, but the blade itself mounts differently.
Do you know exactly what year / part number fan you have? year / part number on the Mark VIII?

This what leads to all the misinformation scattered out there. Not enough details and everybody makes a lot of assumptions. No MarkVIII motor part number exists that is also listed for a TBird so your results would be expected.
 

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Discussion Starter #19
Does anybody know member Johnny Langton ? I sent him a PM because I want to get his input. He hasn't posted in a few weeks. Maybe someone can shoot him an email with a link to this thread.... Thanks.
 
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