kjb

When the truck is in 4 wheel drive is there a light on the dash that comes on?

aviator

Yes there's supposed to be... it is green and says "4WD" it should be in the idiot light strip along the bottom of the gauge cluster and will be roughly above and just to the left of the steering column. It's possible the bulb is burned out or the switch is pooched. It does not dim with the dash lights so that will not be it.

dotcom

in my 91 it is orange and up by the fuel gauge

aviator

You got the gauges without tach dotcom?

PCE91V64x4

In my 1991 base model reg cab it is a green light on lower right side of the center-left gauge.

highridinyota

light should come on unless bulb is burned out or wires have came loose on the transfer case .atleast thats the two problems ive had with my 92

swapped89

mines green and on the lower right hand side of the gauge cluster, just looks like a lil diagram of the drivetrain

dotcom

Yep no tach, wish I had one. Light says 4wd and is amber/orange

dotcom

A few things can cause the light to not come on, one the light itself is the problem. If the light itself is ok it will only come on once the tcase is engaged and the add is locked in place. If either of those items does not correctly engage the light will not come on.

aviator

The most common problem I've heard of is a disconnected/corroded Tcase switch, followed by a burned out bulb, you might have a problem with the vacuum switch on the ADD but if you can feel the front end "bite down" when you select 4hi then that isin't it...

krb90

I had the vacuum lines going to the front dif (add hubs) get pinched and cut the lines. Seems like there was 2 lines.....it's been a while.

Doc.Gneoson

thanks this helps me too as mine's not working as well, one question though, i haven't checked the bulb or transfer switch wireing yet but the truck did used to have a.d.d., a previous owner removed it and added warn premium's, would this affect the light, as if the light is waiting for the a.d.d. to engage(which obviously doesn't happen)??

aviator

Not at all the hubs have nothing to do with the light.

Doc.Gneoson

i was thinking more on the lines of the vacuum switch's you guys are talking about, all my lines are just cut, i'm not shure if the previous owner did a proper job or not i no nothing about a.d.d.

dntsdad

Yes it would. There used to be a switch on the axle tube that that was toggled by the ADD being engaged, and trigger the dash light. I am stripping my ADD off tomorrow and thinking that i will have the same issue as you. I think that simply closing the circuit(twisting the wires together) should allow the T-case control the switch without the need for the front, axle mounted ADD switch.

I'll let you know for sure tomorrow

aviator

Well I did not know that... when you learn something new it was a good day no matter what else went wrong... thanks dad

dntsdad

Sorry i know this thread is old but as an avid searcher I wanted to update this in case someone is searching this in the future like I would be.

Anyway, swapped out the add differential today and obviously the axle monted switch to trigger the dash light went into the trash as well. What I did was find the wires leading to the switch in the engine compartment and wire them together therefore closing the circuit and the light works fine as it should when the T-case in engaged in 4x4.

Look for the green yellow and green/white wire running across the motor in the front towards the distributor and then down along with the oil sender wire. Cut, strip, twist and crimp and as should be well......provided there are no other problems in your system.