4wd drives light not working, but 4wd appears to work

[dmetcalf99]

Another newbie question, I"ve read several reports of when the 4wd lights are working to check the "vacuum" hoses but I just can't find them, does anybody have a picture?

4wd seems to engage somewhat though as the front tires start working

 

[frankiefire702]

What year, kind of jeep?

 

[dmetcalf99]

What year, kind of jeep?

OOPS, that would help, its a '91 cherokee w/ v4.0, ABS, 4wd full time and 4wd part time

 

[frankiefire702]

I know alot of times it's the vaccum mode switch on the front of the transfer case. When you put it in 4wd the vaccum switch is what turns the ligh on and off. The switch runs like 20 bucks at the dealer.

 

[Bounty__Hunter]

Check the front axle on the pass. side and see if it has vacuum lines. If it does, I'll talk you through troubleshooting this problem.

If there's no vacuum lines on the front axle, it's simply a switch problem for however the light is activated.

 

[IcyFridge]

Ah. my 95 had no light, but 4wd ran fine. It could be that the light burned out? I ran with no light for almost 3 years and no problems. However, you should look into getting a haynes manual and look at the wiring for the light on it and route it out.

 

[XJNick]

Hi,

The switch which turns on the light is NOT the vacuum switch at the transfer-case. The transfer-case switch is purely mechanical, while the one for the lamp is electro/mechanical.

The switch is a small blue cylinder (which resembles a typical blue capacitor) and is mounted to the passenger side wall of the engine compartment, just under the coolant reservoir and next to the A/C/Vent/Heater blower motor (near the firewall).

The switch has a single vacuum line and a single electrical connection to it (as it grounds itself when vacuum is present, which illuminates the 4x4 lamp).

If vacuum is reaching the switch when it is supposed to, but the lamp still doesn't work, it is probably just burnt out. :mrgreen:

-Nick :!:

 

[Bounty__Hunter]

Nick, did newer XJ's like the '90 and '91 move the 4wd light switch to the axle disconnect like on the later YJ's? YJ's used both setups, don't know the year they made the switch.

dmetcalf99, let us know if you have the vacuum disconnect front axle and what you found on checking the vacuum.

 

[XJNick]

Nick, did newer XJ's like the '90 and '91 move the 4wd light switch to the axle disconnect like on the later YJ's?

I don't know. I'd assume they're in the same place, as most of the wiring/electrical is the same place on early model year XJs.

-Nick :!:

 

[siminsez01]

how important is the light to you, is it worth the work? my 4wd light never worked on my tj and it never bothered me much.

 

[XJNick]

how important is the light to you, is it worth the work?

Yes, it is worth the work if the cause of the light not working is a loss of vacuum. To ensure the front axle disconnect is engaging properly, you need to ensure the system isn't loosing vacuum. :mrgreen:

-Nick :!:

 

[dmetcalf99]

as soon as I get the jeep back from the dealership I'll reply about the 4wd stuff...

it turns out the booster pump was dead and it was convered under warranty so the dealer replaced it for free (its 3rd time this has happened, the original lasted 10 years, all the replacments last about 1 year - its a good thing the replacements have a life-time warranty)

now I just need to replace the broken bleeder valve!