HELP:::: 4 WD Electric Switch
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Junior User
Joined: May 2019
Posts: 56
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From: Orlando
HELP:::: 4 WD Electric Switch
'99 f150 xlt, 4.6 , 307k miles
Just bought my first used truck- see mileage. Yep, goin' thru it
Problem:
4wd Engage solenoid receives Neg all the time. See my attached picture. Trying to determine if the switch is bad, or the wiring to it.
From left to right, wire 1,3,4 are full time Negative. I don't know what wire 2 is, but has no Neg.
It would seem to me that the switch, which I understand only throws negative, would have one full time Negative coming in, and the others would send negative to solenoids and transfer case motor.....so I'm confused why 3 of the 4 wires are full time Negative.
What can I test or diagnose? Does the transfer case motor send a signal back and forth to the 4wd dash switch? Also, when I turn dash switch to 4wd, the dash light comes on (4wd) but stays on even when switching back to 2wd.
Thank you for your time and effort in...
Logistics Pro
Joined: Jan 2001
Posts: 3,740
Likes: 37
From: Central NYS
Not sure which side of the connector is up when you made your picture of it.
So look at the wire colors going into your connector.
The light blue w/red wire gets current from the instrument cluster to light the selector switch bulb and the black wire provides the ground for that bulb.
One dark blue wire provides voltage to the selector switch and the other dark blue wire provides the signal return to the GEM module.
To test the switch, put your ohm meter on the center two pins of the selector switch.
When in 2H you should see ~3.9k ohms,
4H should be ~ 1.1k ohms,
and 4L should be ~ 360 ohms.
So look at the wire colors going into your connector.
The light blue w/red wire gets current from the instrument cluster to light the selector switch bulb and the black wire provides the ground for that bulb.
One dark blue wire provides voltage to the selector switch and the other dark blue wire provides the signal return to the GEM module.
To test the switch, put your ohm meter on the center two pins of the selector switch.
When in 2H you should see ~3.9k ohms,
4H should be ~ 1.1k ohms,
and 4L should be ~ 360 ohms.
Thread Starter
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Junior User
Joined: May 2019
Posts: 56
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From: Orlando
STILL DIAGNOSING
Thanks to your much valued info-sharing, I have confirmed my electric 4wd switch does meet the ohm values you stated.
I've got negative at the engage solenoid no matter what position the switch, and no negative at all at disengage solenoid.
So I believe I'm paring this down to GEM module or transfer case
motor.
Which would be easiest to check next?
Does anyone know the communication-flow between switch, gem module, solenoids, transfer case motor etc?
I've got negative at the engage solenoid no matter what position the switch, and no negative at all at disengage solenoid.
So I believe I'm paring this down to GEM module or transfer case
motor.
Which would be easiest to check next?
Does anyone know the communication-flow between switch, gem module, solenoids, transfer case motor etc?
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
The switch only addresses the GEM with a request for function.
It does not directly operate the case motor or any solenoids.
Addressing the GEM then the GEM does all the rest.
What issue are you having?
Believe your confused as to what the switch does from lack of knowing how the system works.
Good luck.
It does not directly operate the case motor or any solenoids.
Addressing the GEM then the GEM does all the rest.
What issue are you having?
Believe your confused as to what the switch does from lack of knowing how the system works.
Good luck.
Fleet Owner
Joined: Apr 2008
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From: 0,0,1
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Junior User
Joined: May 2019
Posts: 56
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From: Orlando
GREAT DIAGRAM
Thank you for the wiring diagram....you were right, I had no idea the pecking order of the 4wd system. Now I know the electric switch only sends a command to the GEM much like a thermostat to a furnace.
So, momentarily I thought ok the GEM is not launching the 4wd system, even though it appears to work all the other subsystems just fine. Incredibly, I found no power at Fuse 20.... necessary for GEM and PCM .
Off to the junkyard I go and pulled an identical fuse box. Cheap too....$20 with relays, fuses and a GEM on back. Deal, right?
I completely install it. I decide I'm going to one by one remove each of the junkyard fuses, and replace them with mine, that I know are working. Then comes that uh oh moment....
All of a sudden I'm pulling fuses out of my junkyard find that are "empty/not used" on my old one. I'm like, what are these for?
Then it hits me, is it possible the fuse boxes look absolutely identical, but are "wired" differently? Sure enough, my junkyard find and the one off my truck have distinctly different model numbers! F*********
And you know you can't see that there is a model number distinction unless you completely remove it, as it's on the left side of the unit. Arghhhhh...
Ebay here I come for a fuse box!
I'll try to update progress after I get fuse box in....I'll be really happy if that wakes up the whole 4wd system
So, momentarily I thought ok the GEM is not launching the 4wd system, even though it appears to work all the other subsystems just fine. Incredibly, I found no power at Fuse 20.... necessary for GEM and PCM .
Off to the junkyard I go and pulled an identical fuse box. Cheap too....$20 with relays, fuses and a GEM on back. Deal, right?
I completely install it. I decide I'm going to one by one remove each of the junkyard fuses, and replace them with mine, that I know are working. Then comes that uh oh moment....
All of a sudden I'm pulling fuses out of my junkyard find that are "empty/not used" on my old one. I'm like, what are these for?
Then it hits me, is it possible the fuse boxes look absolutely identical, but are "wired" differently? Sure enough, my junkyard find and the one off my truck have distinctly different model numbers! F*********
And you know you can't see that there is a model number distinction unless you completely remove it, as it's on the left side of the unit. Arghhhhh...
Ebay here I come for a fuse box!
I'll try to update progress after I get fuse box in....I'll be really happy if that wakes up the whole 4wd system
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Fleet Owner
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From: 0,0,1
Thank you for the wiring diagram....you were right, I had no idea the pecking order of the 4wd system. Now I know the electric switch only sends a command to the GEM much like a thermostat to a furnace.
So, momentarily I thought ok the GEM is not launching the 4wd system, even though it appears to work all the other subsystems just fine. Incredibly, I found no power at Fuse 20.... necessary for GEM and PCM .
So, momentarily I thought ok the GEM is not launching the 4wd system, even though it appears to work all the other subsystems just fine. Incredibly, I found no power at Fuse 20.... necessary for GEM and PCM .
Thread Starter
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Junior User
Joined: May 2019
Posts: 56
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From: Orlando
INVALUABLE RESOURCE
Cant tell you what a blessing this site has been for me. Like many I suppose, tight budgets and limited resources force us to learn and fix as we go.
I am most thankful for the input and diagrams that you and others so generously share.
I hope to do my part and share with others where I have learned on this and other past projects.
More to come on this project...thank you again
I am most thankful for the input and diagrams that you and others so generously share.
I hope to do my part and share with others where I have learned on this and other past projects.
More to come on this project...thank you again
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
What you have not done is describe the issue your having so we can see where the issue is likely to be and what to check.
Once you request 4wd a number of actions take place.
Question is how far is it going in the sequence is what is being asked!
Switch to 4H, runs the case motor under GEM control, operates the front Actuator, turns on 4H dash lamp etc.
Where is the fail point? Can be a fuse, a case motor, firewall solenoid, Actuator etc.
Good luck.
Once you request 4wd a number of actions take place.
Question is how far is it going in the sequence is what is being asked!
Switch to 4H, runs the case motor under GEM control, operates the front Actuator, turns on 4H dash lamp etc.
Where is the fail point? Can be a fuse, a case motor, firewall solenoid, Actuator etc.
Good luck.
Thread Starter
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Junior User
Joined: May 2019
Posts: 56
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From: Orlando
FOLLOW UP:::
Thank you for your follow up.
When I launched electric switch:
✓ only dash light would come, but would not go off when returning to 2 WD
✓ negative present at both solenoids
✓ no clicking, or clunking that would indicate the transfer motor engaged. ( Keep in mind, Ive never used 4wd in any vehicle, and don't know all the sounds I should be listening for)
✓ limited diagnosis revealed no power at Fuse 20. Upon reinstalling that fuse, I found it did not lock into place...suspecting corrosion from a leaking windshield, my first repair for this project.
✓ I've removed fuse box/gem and have a fuse box only coming from eBay.
✓ perhaps you can shed light on the gem/pcm operation with the benefit of power at Fuse 20. The truck does start and run.
When I launched electric switch:
✓ only dash light would come, but would not go off when returning to 2 WD
✓ negative present at both solenoids
✓ no clicking, or clunking that would indicate the transfer motor engaged. ( Keep in mind, Ive never used 4wd in any vehicle, and don't know all the sounds I should be listening for)
✓ limited diagnosis revealed no power at Fuse 20. Upon reinstalling that fuse, I found it did not lock into place...suspecting corrosion from a leaking windshield, my first repair for this project.
✓ I've removed fuse box/gem and have a fuse box only coming from eBay.
✓ perhaps you can shed light on the gem/pcm operation with the benefit of power at Fuse 20. The truck does start and run.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Providing the same condition still exist:
Not returning to 2wd from 4wd tells you the case motor did not respond by rotating one position back to 2wd.
Either the case motor did not move or the circuit board it moves has a fault. Did 4wd at the wheel change? That tells you something as well, about what is happening.
This is /was the point of failure not the dash switch or the GEM.
Your work might have introduced more issues, so keep that in mind.
.
Look at fuse 20 in your owner Manuel. It does provide power to the GEM but also Audio, Trans Range select, PCM would all be affected. Are they? If not, that fuse location is not an issue at this time.
See the logic of this?
Good luck.
Not returning to 2wd from 4wd tells you the case motor did not respond by rotating one position back to 2wd.
Either the case motor did not move or the circuit board it moves has a fault. Did 4wd at the wheel change? That tells you something as well, about what is happening.
This is /was the point of failure not the dash switch or the GEM.
Your work might have introduced more issues, so keep that in mind.
.
Look at fuse 20 in your owner Manuel. It does provide power to the GEM but also Audio, Trans Range select, PCM would all be affected. Are they? If not, that fuse location is not an issue at this time.
See the logic of this?
Good luck.
Thread Starter
|
Junior User
Joined: May 2019
Posts: 56
Likes: 0
From: Orlando
FOLLOW-UP::::::
Providing the same condition still exist:
Not returning to 2wd from 4wd tells you the case motor did not respond by rotating one position back to 2wd.
Either the case motor did not move or the circuit board it moves has a fault. Did 4wd at the wheel change? That tells you something as well, about what is happening.
This is /was the point of failure not the dash switch or the GEM.
Your work might have introduced more issues, so keep that in mind.
.
Look at fuse 20 in your owner Manuel. It does provide power to the GEM but also Audio, Trans Range select, PCM would all be affected. Are they? If not, that fuse location is not an issue at this time.
See the logic of this?
Good luck.
Not returning to 2wd from 4wd tells you the case motor did not respond by rotating one position back to 2wd.
Either the case motor did not move or the circuit board it moves has a fault. Did 4wd at the wheel change? That tells you something as well, about what is happening.
This is /was the point of failure not the dash switch or the GEM.
Your work might have introduced more issues, so keep that in mind.
.
Look at fuse 20 in your owner Manuel. It does provide power to the GEM but also Audio, Trans Range select, PCM would all be affected. Are they? If not, that fuse location is not an issue at this time.
See the logic of this?
Good luck.
I do see the logic, yes. I did mark front drive shaft with white out when putting in 4wd, to see if case motor engaged...it did not. I felt like when turning the switch from 2 to 4wd that absolutely nothing happened...no relay click, no thud..nothing. You mention a "circuit board" in your reply.....were you referring to GEM or something down at the case motor? Sorry this is so foreign to me...never worked on 4wd, but Im a fast learner and appreciate instruction.
I will report back after I get replacement fuse box installed over weekend.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Get the fuse distribution back in place, be sure all feeds work then we start all over again.
To diagnose system failure before making any more changes going in directions that may not apply..
At the moment your in a suspension state.
Good luck.
To diagnose system failure before making any more changes going in directions that may not apply..
At the moment your in a suspension state.
Good luck.