Jeep came back from the shop. Should I return iut for a 4wd light -
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Unread 05-04-2010, 04:40 AM   #1
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1993 ZJ 
Join Date: Dec 2008
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Jeep came back from the shop. Should I return iut for a 4wd light

Hey guys. I just got my betsy back home.They replaced the 4wd vacuum actuator and got the thing running well. Well now I have no 4wd indicating light. SO i do not know if I am in 4 high or not. I know guys have told me that you feel a difference but right now with oversized tires rubbing on the inside I cannot differentiate that from 4 wheel drive kick.

Where should I test to see if its just a blown light or fuse before losing my jeep for another 3 days at the shop.

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Unread 05-04-2010, 05:33 AM   #2
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1989 YJ Wrangler 
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Did the light work before they worked on it? Depending on the year, if its the later one with the switch on the housing, the plug may not be contacting well enough, or if its the old style where it uses vacuum to activate a switch to tell the light to come on, there may be a vacuum leak. If all that is fine, then best that I recall it isnt very hard to take the dash off, then the assembly with the lights will come forward enough after you remove a few screws and you should be able to get the bulb out and look at it.
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Unread 05-04-2010, 05:41 AM   #3
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1993 YJ Wrangler 
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Location: Raleigh, NC
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Go look at the shifter motor housing and see if they forgot to plug it back up somewhere. Mine got knocked off on a rock years ago. I just filled it with JB Weld. I wouldn't mind seeing that little light but they don't sell the switch anymore. At least doesn't.

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Unread 05-04-2010, 06:03 AM   #4
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The 4WD dash light on my 1988 YJ Wrangler receives its turn "on" juice from a little unit which is bolted onto the firewall from the engine bay side.
The switch is located to the right side of my battery tray area and is identified by 2 black electric wires , one black vacuum hose supplying vacuum / no vacuum signal , and a pale blue plastic housing.

It is my understanding that when you switch to 4WD , the black vacuum line should apply vacuum to the blue plastic switch .
That signal would turn on the switch to allow 12v to flow from :12v black wire supply juice -->thru the switch --> out the second black wire --> to your dash light "ON".
Lack of vacuum signal to the firewall switch ( vacuum comes from your new vacuum actuator motor ) could be caused by lack of poor hose connections or leaky vacuum hose.
My vacuum motor had 3 vacuum hose nipples.
The nipple which is outermost / closest to the tire is the disconnect signal My vacuum hose is green . It forces 2WD.

The middle nipple is the "turn on 4WD " via vacuum signal when you thrust the shift lever into 4WD. It is the nipple receiving vacuum via yellow vacuum hose / rubber boot.

The 3rd nipple is closest to the drive shaft / middle of vehicle. It sends vacuum signal to the firewall blue plastic switch after the vacuum actuator motor has received vacuum signal from yellow hose to move the inner fork lever.

If you apply a handheld vacuum gauge to the 3rd nipple when you put vehicle into 4WD , it should have vacuum signal if the yellow hose feeds vacuum to the motor and your new diaphragm is intact.

I would start at 3rd nipple to be certain that vacuum is sent to the pale blue plastic switch from the vacuum actuator motor.
I could reach the 3rd vacuum nipple w/o removing wheel nor jacking vehicle.

Green hose sends vacuum to outer 1st nipple to make it 2WD.
Yellow hose sends vacuum to middle 2nd nipple to make it 4WD.
Then , Black hose relays vacuum via most inner 3rd nipple to pale blue switch .
Then pale blue switch sends 12v to tell dashboard to say '4WD".
Hope this helps.
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Unread 05-04-2010, 08:31 PM   #5
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1993 ZJ 
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I get home late from work but will take all that info with me to the jeep . Early sat morning. Weatehr permitting.
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Unread 05-04-2010, 08:43 PM   #6
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1989 YJ Wrangler 
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It would really help knowing what year Jeep you have. 87 -90 used a vacuum operated switch on the firewall for the light and 91-95 used a switch mounted to the vacuum disconnect.
BTW I have a vacuum switch for the firewall for sale if someone needs one....
89' YJ Larado 4.0L,AX15
05' Grand Cherokee Limited, 2"OME lift and a Hemi.
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