4wd not working on my 1996 ssrx hilux surf

[eoinr23]

Hi,
Ive recently bought a Toyota Hilux surf ssrx,3.0TD automatic. I bought it with the 4wd not working,and have spent a little time going through it.There is power at the fuse for 4wd but none at the switch,and obviously none at the actuator or vsv valves. Also there is no lights at all in the dash board indicating 4wd. My main question is;is there a 4wd control unit ? and if so where is it located? Any help at all would be greatly appreciated...

 

[fourwd1]

Does it have the ADD 4WD system (there will be an assembly on the front axle adjacent to the diff, drivers side)

 

[eoinr23]

Hi fourwd1,
Thanks for commenting. Yes it does have the ADD system on it as far as i am aware,although Im farely sure its an electrical control problem that Im having. Nothing seems to be getting the signal to engage and there is no lights on the dash illuminating to signal which 4wd selection is being used.If anybody new what controls both the lights and actuator and ADD that would be great

 

[fourwd1]

The ADD works off of the 10A GAUGE fuse.
There are 3 different switches and 1 relay that control operation.
One switch is on the ADD assy and closes when the ADD actuator slides into position to lock the front axle.
Two more are on the t-case, one for the lever position and one for pressure.
The relay controls the 2 VSV's that lock/unlock the ADD actuator.

 

[eoinr23]

Thanks again,just trying to get a better understanding of the system.So as you engage the switch on the gear lever,current is sent to both the vaccum valves to engage the front axle and current is sent to the actuator to engage 4wd drive at the gearbox,is that basically the circuit? On my Hilux there is no power getting to the switch and therefore none of the 4wd components.Would you have an idea of where the power gets to this switch and where it travels to next when the switch is engaged? I really need a good wiring diagram! Any help would be great,Thanks

 

[fourwd1]

A PDF of the circuit is on the net, just search.
You want one for an auto trans, it's slightly different from manual version.
The lock/unlock commands to the VSV's are via the relay. The switch on the actuator is just to light the indicator light (along with the 2 t-case switches).

 

[fourwd1]

12V from the 10A fuse goes to one side of the indicator bulb and pins 6 and 1 of the relay in 2WD or 4WD, so if you don't have that, you have a supply problem.