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Unread 07-11-2013, 09:51 AM   #1
dirtbike7992
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4WD Help Needed

Hey guys,

I picked up another Jeep (90 YJ 4.2) project a few weeks ago. In the midst of the rebuild I have realized that the 4wd seems to work but the light on the dash doesn't. I know a lot of people would say "who cares it is just a light" but I am OCD about that stuff and want it fixed. I haven't looked at anything yet involving the problem so I figured I would get an idea here before diving in. Could it be as simple as a bulb in the dash or some faulty in the vacuum system for the 4x4....Thanks for the advice in advance

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Unread 07-11-2013, 09:57 AM   #2
jokerchief462
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It is vacuum operates if you are still stock. Passenger side firewall betwee back of valve cover and batt tray. Look for a bracket that has a blue thing in it. Has a vacuum nipple and a wire. That is how it is activated. At least an 89 newer models may be different.
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Unread 07-11-2013, 09:57 AM   #3
Randonexplosion
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It could be the bulb, but I believe the switch for the light is on the firewall underneath the battery somewhere.
vacuummap.gif

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Unread 07-11-2013, 10:31 AM   #4
Michaelgoesrawr
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Quote:
Originally Posted by Randonexplosion
It could be the bulb, but I believe the switch for the light is on the firewall underneath the battery somewhere.
Next to the battery. It's easy to see because it seems so out of place. Easiest way to see if its your bulb is okay is to turn the ignition on so your dash has power. Unplug the wire from the switch and ground it out and see if your bulb comes on. That will do one of two things, it tells you if the bulb is good and that you need to further problem solve. If your light proves to be good, check and make sure the connection to the switch is clean and plug it back in. Now you unplug the vacuum harness from the switch and grab a length of vacuum hose and connect it to the switch. Suck on it or use a vacuum pump and see if the light comes on. If it does you have a vacuum line problem after the switch.
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Unread 07-11-2013, 10:36 AM   #5
Randonexplosion
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Now that I think about it I can picture it. Dont know how I could forget with all the time I spent under my hood
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Unread 07-11-2013, 11:00 AM   #6
Michaelgoesrawr
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Quote:
Originally Posted by Randonexplosion
Now that I think about it I can picture it. Dont know how I could forget with all the time I spent under my hood
Exactly! You're thinking of that vacuum bulb res thing under the battery.
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Unread 07-11-2013, 12:20 PM   #7
dancytron
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Quote:
Originally Posted by Randonexplosion View Post
It could be the bulb, but I believe the switch for the light is on the firewall underneath the battery somewhere.
Stop posting this diagram!!!!!!




It is wrong. It is closer to a 1990 and before, but is missing the checkvalves, which are necessary for it to work. It is not close to the 1991 and older.

Accurate diagram for 1990 and before.

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Unread 07-11-2013, 12:23 PM   #8
Randonexplosion
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Whoa sorry Boss. A 5 second Google search brought it up.
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Unread 07-11-2013, 12:30 PM   #9
dancytron
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That's okay, sorry if I came across harsh.
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Unread 07-11-2013, 01:10 PM   #10
Michaelgoesrawr
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Quote:
Originally Posted by dancytron
That's okay, sorry if I came across harsh.
The other one has pretty colors though.
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Unread 07-12-2013, 07:35 AM   #11
dirtbike7992
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Thanks for all the responses! When I get a break from work I will have to check it all out. I never even thought of just grounding out the switch to see if the light is working....duh....I will check into it and see what comes up. Hopefully it isn't anything too ridiculous....I fixed enough on this dang thing already. Thanks again for the advice !
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Unread 07-12-2013, 10:57 AM   #12
bpounds
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Anyone know a good source for the check valves in that harness?
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Unread 07-12-2013, 12:34 PM   #13
Anticanman
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You could do what I did.

http://www.jeepforum.com/forum/f12/t...80/?highlight=
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