463 diff lock electrics
Hi, I'm new to the forum, but not to G Wagens. Got an M reg 300GEL belonging to a mate here with a diff lock fault he's asked me to look at. The rear, and sometimes centre diff locks are in when not selected, and can't be de-selected. The switch lights aren't on, but the diff lock in indicator lights are. The only way to get them off/out is to unplug the switch panel, or the individual control solenoids.Thought I'd swap some bits with my K reg diesel one to fault find but it's different. The petrol one with the problem has a control box with the 3 diff lock switches in behind the panel, where as my older diesel one has 3 individual switches. Anyone got any ideas? Any help appreciated. I'm an agricultural engineer by trade, G Wagens are a bit of a hobby, currently restricted myself to owning 3!
Without looking into it too much, I would have suggested the control box as the unit at fault, but how to test and prove this?
I would tackle this problem by simulating conditions for engagements withe the vehicle safely mounted on axle stands on all fours.
Checking all wheels, individually, are free to turn, engage the first button, which is the centre diff. (Ignition on), you should hear a brief moment of a vacuum pump working, you should see firstly, the the amber light telling you that a relevant switch is on, then after some turning of the wheels on each axle, the diff. engagement (Red) light is illuminated. Switch off the diff. lock and confirm if these light extinguish, if not there is a fault to locate. Follow on, repeating the diff. lock switch engagement and move on to the rear diff. lock switch, the rear axle should lock up and both rear wheels should turn in sink; progressing to the front axle.
As proven, in the time honored, traditional manor, tap the control box to check if the there is a change in behavior.
Apply independent power to the axle solenoids to check these are freely working, engaging and dis-engaging.
If after all that, there is no clue, we need to dig out the manual or go to the American technical site. Try this site: http://www.mercedestechstore.com/463.htm
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Thanks for that Rakesh. Its been a week or two since I last looked at it, but I remember that you can't select any of the diff locks, ie no amber lights, and the rear is always in, red light on and confirmed diff lock in by jacking the vehicle up, and the centre is intermittent but if the red light is on the diff lock is in. The front one does nothing. Some of the time the electric vacuum pump runs constantly. The only way to de-select them is to unplug the control unit, or the individual solenoids, ie there's power getting to the solenoids from somwhere. I'll have another look, and give that website a go. I too suspect the control unit, but I'd like to confirm this some how as the unit is circa £400. Thanks again for your help, I'll keep you posted.