fan switch

[cutt]

has anyone put a switch on the cooling fan to turn it on manually?

[LincMercLover]

Nope, but want to. :D

Fairly easy. I think it's a red/orange wire under the dash that needs to be spliced into with a switch and then groud the switch.

[cutt]

anyone know how to exactly?

[jgc61sr2002]

cutt - Just curious, why would you want to do that?

[LincMercLover]

To be able to cool the car during staging.

[WolfeBros]

Good reason LML........that one makes sense to me.
I too was wondering WTF for ?

[Zack]

I will ask my mechanic how to do it today. I believe you splice a wire in the A/C circuit. That was the case on my 1989 Trans Am. Ill keep everyone posted.

[engine23ccvfd]

I dont get it. Why do ya'll want to turn on the fan? Which fan?

[SergntMac]

Be careful here, make sure you get specific instructions on which wire to put the power into, or, consider adding diodes to prevent the 12v from traveling up the other wires. "Flashback" can get expensive.

[TripleTransAm]

Originally posted by engine23ccvfd
I dont get it. Why do ya'll want to turn on the fan? Which fan?

Which fan?
The one sitting in the stands, waving the pom-poms and going "Go LML! Go Cutt! Go Mercury! YAY!"... :lol:


Seriously...
the cooling fan is controlled by the PCM to come on at certain temperatures - from the wiring diagram it's hard to tell if it's a constant speed motor or if the PCM can control its speed.

Looks like the red/orange wire IS the one to play with, and it would appear that the PCM controls the fan by grounding this wire through itself. What's not clear is if the grounding is a definite on/off function, or if the PCM modulates the ON-OFF at a pre-determined frequency to establish a fan speed.

It shouldn't hurt to try grounding the fan side of the red/orange wire and leave the PCM side of the wire free-floating. If the fan spins up too fast you'll know the PCM is the one who determines the speed, and then you might want to restrict the amount of time the fan operates at this speed, to avoid burning up the fan motor.

I would only see this mod helping if one wanted to cool the engine in the staging lanes with the engine off... unless the Ford PCM already actuates the engine fans with the ignition off?

[RF Overlord]

Originally posted by TripleTransAm
unless the Ford PCM already actuates the engine fans with the ignition off?

I remember being in the driveway when my wife came home (I don't THINK she was aiming for me...) with the A/C on, and when she turned the car off, I distinctly heard the fan(s) spool down...

[TripleTransAm]

Originally posted by RF Overlord
I remember being in the driveway when my wife came home (I don't THINK she was aiming for me...)


:lol: :lol: :lol:

BTW, I think I should have said engine FAN and not FANS in the previous post. I don't think I've ever had a good look in that area before (heck, I just found out where the damned thermostat is located this past Saturday evening...)

I'm working on my foglamp mod this evening and I'll have a look. If I get to fire up the car, I'll try to establish if fan operation continues after engine shutdown and ignition off.

[WolfeBros]

Originally posted by SergntMac
Be careful here, make sure you get specific instructions on which wire to put the power into, or, consider adding diodes to prevent the 12v from traveling up the other wires. "Flashback" can get expensive.


Very good advice. I would not add a switch without putting in a diode. If you don't know what a diode is or what it is for, you probably shouldn't be making this mod. IMHO

[LincMercLover]

From what I've looked at, the red/orange wire is apart of the high speed relay for the fan.

[Zack]

In the past, fans have been activated by a switch threaded into the A/C lines. When the switch detects elevated line pressure, it forms a ground which triggers a relay, turning on the fans. If it is the same in the Marauder, you simply splice the wire, run it to a switch under the dash where the other side is connected to ground and you are done. It will never interfere with the computer, and you can have the switch in any position when the A/C is on and the fans will run. I will investigate tomorrow.

[engine23ccvfd]

THe fan is multiple speed so when you get it to turn on by closing the ground how do you control which speed it comes on at (information from service manual says GM/CV have variable speed fan but doesnt mention MM) hope this helps.

[cutt]

so which wire should we ground?

[RF Overlord]

Dudes:

If it's a variable speed fan, then it could use what's called PWM (Pulse Width Modulation) to vary the speed. For example, the PWM circuit could turn the DC to the fan on for a set period of time, say 500 mS, then turn it off for the same time...this 50% duty cycle would cause the fan to operate at half speed. Varying the percentage of "on" time versus "off" time allows an almost infinite range of speed...the heater fan in my T-bird works that way...

SO...

Simply grounding the wire on the fan side "may" cause the fan to run at full speed, but it's also possible that it was not designed to run with 12VDC applied to it full time, and it may not like it...

Or, it could be a simple relay off/on circuit and I'm full of it...maybe TooManyTransAms could look into this for us?

[TripleTransAm]

Originally posted by RF Overlord
If it's a variable speed fan, then it could use what's called PWM (Pulse Width Modulation) to vary the speed.


Judging by the circuit diagram, looks like the PCM just grounds that lead from the motor. So, if it is a variable speed motor as has been claimed, the only way to do this is to PWM the shorting-to-ground, as was mentioned earlier. For that reason I think grounding the wire may simply run the fan at top speed (I suspect the 100% grounding PWM will result in full fan speed... it would be wasteful to select an odd PWM value like 75% for max allowable fan speed for no good reason... simply a waste of PCM resources, in my opinion).

[engine23ccvfd]

Just to clarify the manual specifically states the fan on a CV and GM is variable speed...I could not find any mention specifically relating to the MM fan....Someone could compare part numbers and find out I will do some more research tomorrow if needed. Got take the wif to the medical center for some testing wish us luck!

[LincMercLover]

It is variable speed, and I think grounding the red/orange wire will kick into high speed. This is what I've heard from the Mustang forums...

[CRUZTAKER]

The talk of the track last night was...."damn it's hot, I wish I could rig this fan to run!"

Well, I went through 10 bags of ice and the mere sitting 25 minutes per run just to knock the temp down by 1/2....I thought to myself, I am doing a search tomorrow on the MM net.

All I found was this thread, and one other with less input HERE (http://www.mercurymarauder.net/forums/showthread.php?t=496).

This thread NEEDS to come back, cause this is gonna be a loooong hot summer if some of us can't figure out a quicker way to cool our motors, and run our fans in the staging lanes AND pile on bags of ice.

ALL I WANT TO DO IS RUN A SWITCH AND A NEW 10AWG WIRE TO GROUND TO THE APPROPRIATE WIRE AT THE HARNESS CONNECTOR, UNDER THE HOOD, NEAR THE FAN SHROUD COVER.

[FiveO]

I have a fan switch like this in my 99 SHO.

Really helps at the track. Keep those fans running!

[CRUZTAKER]

bump....;)

[Zack]

Keeping the fan on while staging only makes sense if you are running an electric water pump.

[FiveO]

Keeping the fan on while staging only makes sense if you are running an electric water pump.

makes sense.

I use mine in my SHO between runs too.

[Smokie]

The fan is a 12 volt dc. motor, two wires red and black go directly to motor, the motor does not have multiple windings so it is not a multi-speed motor, you change fan speed by either regulating the D.C voltage to motor, or by regulating the duty-cycle (turning voltage on and off)

Running the fan at a constant 12 VDC should not hurt the motor, however since the PCM is the ultimate controller I do recommend the use of a diode on the hot side to prevent any flashback to PCM.

[RCSignals]

.

I can understand the idea of cooling during staging, but if the car is hot, the fan should be on anyway.

[CRUZTAKER]

The fan is a 12 volt dc. motor, two wires red and black go directly to motor........I do recommend the use of a diode on the hot side to prevent any flashback to PCM.Nice, and more to the point this time. Thanks Mr. X!




.

I can understand the idea of cooling during staging, but if the car is hot, the fan should be on anyway.This is exactly my point.


With my lack of motorhead IQ, Zack went over my head as I have no idea what he speaks of.....:stupid:

I see many old school hod rodders rig the radiator fan to merely blow air across the block to aid in cooling the motor down. In addition to my use of ice in key areas (such as the steel cold air intake cover), I would think this would work.

[TripleTransAm]

Running the fan at a constant 12 VDC should not hurt the motor, however since the PCM is the ultimate controller I do recommend the use of a diode on the hot side to prevent any flashback to PCM.

Good point, Smokie! However, is it really the PCM that controls the fan directly or does it do it through a relay? (I'd look in the electrical manual, but all my $#!t is packed away for the upcoming move).

[RCSignals]

If you really want to cool the engine compartment, just direct the AC ducting that way :lol:

[David Morton]

In the past, fans have been activated by a switch threaded into the A/C lines. When the switch detects elevated line pressure, it forms a ground which triggers a relay, turning on the fans. If it is the same in the Marauder, you simply splice the wire, run it to a switch under the dash where the other side is connected to ground and you are done. It will never interfere with the computer, and you can have the switch in any position when the A/C is on and the fans will run. I will investigate tomorrow.Sounds right to me Zack. Send me a PM or e-mail 'cause I want you to do my grille, badgeless. I like that very much, and have NBCshooter's 3/4 picture as a desktop right now. Try to imagine what that'll look like on "Quicksilver". Dark lens covers for the headlights and signals, too.

BTW, some systems in the past just had a relay that turned the fan on when the A/C was on period. Anybody know if the fan will come on with just key on and A/C on? I remember teaching a greenhorn technician to disconnect the battery one time by just getting inside the car turning the key on and swtching on the A/C. He got his knuckles skinned and always disconnected the battery after that.

[Smokie]

Good point, Smokie! However, is it really the PCM that controls the fan directly or does it do it through a relay? (I'd look in the electrical manual, but all my $#!t is packed away for the upcoming move).
Steve, the cooling fan does not use a relay, it uses a 50 amp maxi-fuse which also works like a circuit breaker, I don't believe that it is directly connected to the PCM because the PCM is a low current master control device that sends and recieves information via low voltage, low current transmissions, there is a fan module located on the fan shroud that I believe is the one that senses air temp and regulates fan activation, I also believe that there are temp sensors on the engine that send info to this module to regulate fan activity. Javier.