4wd u/s again !!

[bensonsnuts]

Yet again my 4wd has bit the dust.
It's done it before & been blamed on split vaccum hoses & dodgy wiring etc.
Eventually it's always come back on ,on it's own.
This time it seems to have gone for good......it's spent about 4 days in 3 seperate garages & had the best part of the surf forum underneath it at Langdale.
The ?????? things been tested to death.
The switch on the gear lever works
The relays behind the centre console are ok
The wiring to the solenoid all checks out............
& then everybody seems to step back & scratch their head.

Now I'm not really into mechanicals at the best of times.....but it seems to me theres not an awful lot of moving mechanical parts left to check .
Am I right in thinking that there is a short front prop which should lock at both ends to invoke the 4wd ?
To my way of thinking it can only be the solenoid not locking into place .
Is there any way of testing this ? Everybody seems reluctant to touch this.
Help !! I'm really p*ssed off & I'm supposed to be away in the Lake District for an offroad weekend at the end of May.
It seems impossible to find anybody in the NE of England who knows anything about the 4wd system on the surf.

[bensonsnuts]

As a further note to this......when the 4wd worked...I always used to get the light on the dash......I don't get this now the 4wd is u/s . What triggers the signal in the dash ? Because it obviously knows its not working .
I also get a voltage drop indicated on the dash when I try to engage the 4wd.

[NiftyNev]

Have you seen this -

http://www.toyotasurf.asn.au/techsite/add.htm

Neville

[Guest]

Have you seen this -

http://www.toyotasurf.asn.au/techsite/add.htm

Neville

From looking at that, it seems that the light will only come on if the 4WD engages as it is switched on by a switch in the Diff casing which is triggered by the ADD sleave moving across.

So in this order it is operated:

1. Press the switch.
2. This switches the ADD relay
3. The ADD relay triggers the VSV
4. The VSV (either into 4WD or out of 4WD) allows the vacuum from the storage tank to move the sleave and engage or disengage the ADD.
5. The movement of the ADD sleave triggers or releases the switch in the diff casing which illuminates the Dash indicator.

So I would think the best way to check where the fault is would be to go through things in that order.

1. Check power to and continuity though the switch
2. Check that the Relay clicks then check the circuit through it.
3. Check power to the Vacuum Switches. If they operate, check that there is vacuum present by removing the hoses in turn.
If there is vacuum present and it is being triggered when the button is pressed then the problem must be the sleave in the Diff or it's actuator.

Hope this helps, to be honest I'm trying to make sense of it myself and going back to old engineering logical fault finding.

Cheers

[bensonsnuts]

Thanks for that chaps, I printed it out & marched back down the garage with the info.

The mechanic seems a lot more optimistic about sorting the problem now. I've got the surf booked in for Tues ...so fingers crossed....I'll let everyone know if it's fixed.

[NiftyNev]

Andy

You are on the right track.

I think there is also a second switch on Transfer Case.Remember reading something about this.I'm not sure but I think both switches need to be activated before light will come on.

Not much help but if the ADD Actuator is working and still no light then it may be worth looking at the Transfer Case.I may be way off track as well.

Neville

[bensonsnuts]

Andy

You are on the right track.

I think there is also a second switch on Transfer Case.Remember reading something about this.I'm not sure but I think both switches need to be activated before light will come on.

Not much help but if the ADD Actuator is working and still no light then it may be worth looking at the Transfer Case.I may be way off track as well.

Neville

Well, the garage checked everything !! & drew a blank !!!!
That left me going to a 4x4 weekend with a 4x2 surf

Spent last weekend over near Keswick in the Lake District with a great bunch of folks.
Did a couple of green lanes & competed in a small trial with only 2wd.
On the Monday a couple of the guys decided to check out my 4wd & with the aid of the stuff I'd downloaded from the Aussie site worked out what all the various systems did.
After some comment on the over-complicated & in-effactive systems needed to engage 4wd ....they found a split vacuum hose on the top of the transfer case & a dodgy elec connection to a switch.
After repairing these & frigging various systems to lock the front diff etc ,they concluded there was a dodgy relay in the comp control & this couldn't be fixed in a field.
Since I got home I've been trying to find someone to test & repair this , but unfortunately the place I used for the rear window relays has closed !!
Many thanks to Ollie & Bewick of the NE 4x4 club tho'
They did more for my car in a few hours than several garages have done in a few days.