If your 4WD switch looks like this AUTO, 4HI, 4LO then...

[Opera House]

Do you have any real knowledge of this? You may have heard some wild tales from someone who hooked on to a wrong wire. Basically it is impossible to get more than three amps through this 5 1/2 ohm coil. If full power was applied at 14 volts, that would give a current of only 2 1/2 amp. And I have measured it. I'd like to think 30 years in electronics has taught me something, but I'm open to new ideas.

 

[dogfriend]

V=I*R or I = V/R = 14/5.5 = 2.55 Couloumbs/ sec = 2.55 Amps.


Yep, there was this guy named Ohm who came up with Ohm's Law which is a pain in the butt for a first year physics student, but is useful in this case.

Actually, the current supplied to the electromagnetic clutch is in the form of a PWM signal, but Opera House is correct that the max amount of current is governed by the resistance of the coil itself.

 

[zzimzimma]

Ok you guys got me confused now...I've read in a few of the other post that people are burning up 20 amp switches. Something is wrong there!

Regardless, I wanna use a relay...Its the safest way.

87 and 30 will be the brown wire

85 is ground

86 will go to a switch

the switch will have 12v power to it on the other leg

Is this correct?

 

[Opera House]

I can't believe that no one here has enough ambition to hook up a meter and measure the amperage and resistance. I've had the GEM and the transfer case apart and the components are consistant with the amount of current I have reported. It only operates an eddy current clutch to ramp some steel balls. Maybe mine is defective or the only 3A clutch ever made, but at least I have made measurments. Someone needs to produce some printed documentation or make some tests before this is discussed further. As I said before I have made the measurments.

The above circuit is correct.

 

[zzimzimma]

Opera House...

I believe you man...But why are those people burning switches up?

The other reason I wanna use a relay is so I don't extend the wiring in the circuit. I'll mount the relay under the seat which doesn't add any distance to the original wiring. The only addtional wiring I'll have is the travelers to the switch which has nothing to do with the actual brown wire

However, I will hook my meter up to this once I'm done to measure the draw

 

[Opera House]

Switches for automotive applications can be very poor quality because they usually have no agency approvals like UL. I helped a friend wire up his Cobra and he used LUCAS switches. They don't call them The Prince of Darkness for nothing. Those switches are junk. All common switches form an oxide layer on the contact surfaces. Mechanical action and voltage are used to break down the oxide layer. In extreme cases with an old switch, this can cause heating. Switches can have internal lamps and a miswire can cause problems. I'm not going to speculate so little information.

One thing that hasn't been talked about is the use of the switch. I can see someone here spinning their wheels and throwing the switch on at the same time. This would probably cause undesired mechanical stress since the GEM probably applies power gradually. Another problem could be when full electrical voltage is applied to the clutch and then it is interrupted by the relay. At the time current is interrupted to the coil, the magnetic field collapses and tries to generate enough voltage to maintain that last current flow. This creates an electrical spike of many hundreds of volts. This is what gives the arc when a wire is removed from a powered coil. In some devices like the IAC, there is an internal diode to snub this voltage. Devices to control this voltage may be in the coil assembly or the GEM. It is not a good idea to switch the coil when electrical power is applied. Some snubbing device probably should be included in this circuit. When warmer weather comes I'll put a scope on this to determine the best recommendation that does not interfere with GEM operation, if needed at all.

I was curious about what would actually happen when a switch was used way beyond it's ratings. Took a UL rated 3A 125V AH toggle switch and submitted it to 25A for an hour. Temperature stabilized at 229F, voltage across the switch was 0.187 @ 25A which calculated out to be 0.0075 ohms for the switch. This was equivalent to dissipating 4.7 watts of power. This is an extreme case but this good quality switch was handling it very well. The switch was operated several times with no change in current, no indication of burning or potential plastic failure.

 

[Robert]

My 15A AutoZone lighted switch doesn't even begin to get warm after driving around in 4 High for 2 hours. If someone blew out a 20A switch then something was not hooked up correctly. Incidentally, the current rating of the 14 guage brown wire that Ford uses is only 13.13 amps. If there were 20A going through that wire, it would have melted the insullation on the wire long before the switch was damaged.

 

[Premier]

Picts dont work!!!!!!!!

 

[Premier]

--------------------------------------------------------------------------------
Originally posted by Campo
stadx2,

I'm not an electritian so could you post a quick diagram of how you wired the relay, fuse and switch with the brown wire from the C200 connector

TIA
--------------------------------------------------------------------------------

Originally posted by stadx2
Here ya go..........

Does anyone have this diagram?

 

[Lee S.]

I just did this mod two weeks ago. Like others, I found the brown wire in the dash. If you remove the radio you will find it to the right of where the radio was. I just cut it and ran wires to a switch mounted under the drivers side dash next to the center console. No relay, no fuse and no hunting under the seat for the brown wire. Use a lighted switch and you can see when more power is applied to the front wheels (when the switch is engaged (ie in 4wd auto) that is).

Lee

 

[Blee1099]

The brown wire mod does not work on 95-96 Explorers.. since you already have 2WD.

 

[Premier]

Originally posted by Blee1099
The brown wire mod does not work on 95-96 Explorers.. since you already have 2WD.

It says I should have 2wd.. but I dont trust me I am lifted and locked now, and the front wont dis-engage. The T-case is being powered for some reason.


BTW, I got the diagram listed above. I will post it in here from work on Monday. And I found my brown wire under the passenger seat. Will start on it this week.

 

[Blee1099]

Ahh sounds like a vacuum problem since the front axle is vacuum actuated on the 95-96. JDraper did a front locker on Explorereb96 and if I remember correct she has 2WD in the front.. you should give him a e-mail and see if he could help with your problem.

 

[Premier]

Its not a vacuum problem. The vacuum disco is working just fine. The problem is my T-case is not disengaging. *shrug*

 

[JPA1982]

WOW, just spent hrs reading all these replys and the ones that join on and off of it, such as GJarrett Front locker thread and the auto 4wd . etc,

lol, so i think i'm confused enough from all the back and forth and other confused peoples remarks that i can do this sometime quickly this weekend, lol, any wayz,i know old thread but a good one, helps us eventually lock the front or just have 2wd when we want it, i.e. HIGHWAY=Road trips,

 

[first explorer]

2002 explorer

You could use a relay, but at .6 amp current draw almost any switch would handle that. The amp ratings for switches are usually stamped on them. The brown wire that interrupts the clutch is not very large, (I would guess 16 awg) so putting in a 30 amp relay or switch is pointless unless you just wanted to be real safe

do you think my 02 explorer has the same brown wire?

 

[dogfriend]

do you think my 02 explorer has the same brown wire?

Yes, check out my reply on page 16 of this thread. Find the brown wire on the transfer case

This mod worked for a 2003 so it should work for a 2002.

 

[Lee S.]

Also check out Jared's simplified write up of the 'how to' on this mod:

http://www.explorerforum.com/forums/showthread.php?t=106593&page=2&pp=20

Lee

 

[first explorer]

thanks

Yes, check out my reply on page 16 of this thread. Find the brown wire on the transfer case

This mod worked for a 2003 so it should work for a 2002.

hey! it worked, the only problem i have now is I can't help but lay rubber all over the place.

 

[dogfriend]

hey! it worked, the only problem i have now is I can't help but lay rubber all over the place.