Diff Lock light problem

[land864]

Just had the clutch done by a mechanic on my 86 Isuzu County.

Feels much better without the judder:)

Problem , post clutch repair , is the Diff lock Light

When decelerating or braking , the Diff lock light flickers on.

It very occasionally does it while just driving along but is made worse when decelerating or braking. Almost like something is moving forward under that motion.

When it was picked up from mechs by a friend who pointed it out to said mech, he stated that the flickering diff lock light was caused by existing dodgy wiring and an untidy firewall fusebox.
He is correct in that the fuse box wiring does look like it needs a tidy up and I am having that done soon.

He did say if I wasn't happy to just bring it back but the issue there is that it's about an hour away , up the country.

Even with the messy wiring previously, I had no issues at all with the diff lock light. Worked perfectly on engage and disengage.

Now when I pull out the vacuum switch to engage the diff lock , the light does not come on.

I don't think the diff lock is engaging , just getting a spurious signal from somewhere.

Having collected it from my mate on Sat morning and then spending the whole weekend using the County , I did not get a chance to take a proper look until last night.

Pretty sure I can see where the vaccuum lines go in and can see a local earth wire and a green/black? wire connected to a switch? over the vaccum line/diaphragm unit.

Any ideas on what could be causing this.

If it's an easy fix I will do it myself but if problemmatic will take it back.

Pete

[steveG]

First thing to do is to confirm if the CDL is actually engaging.

Jack up one front wheel so its clear of the ground and can turn.
With CDL off, handbrake on, and the transfer in neutral you should be able to turn the raised wheel.
The center diff will allow the front end to turn independently of the rear (which cant as its on the ground and handbrake on).
Engage the CDL and you shouldn't be able to turn the wheel (as the front end is now locked to the rear).

If yours is a 4 speed, then the CDL switch isn't hard to remove and test. It just unscrews from the gearbox housing.
I've had 2 of those switches fail in mine since I got it back on the road in April. The CDL one, and also the reverse switch. They are exactly the same part.
Not sure if its a common failure as mine were from a donor gearbox that had sat outside for a while, so that could have been part of the issue.

[isuzurover]

I assume (based on year) that yours is a 5-speed with LT230?

There is a switch on the forward extension of the t-case (which you can access by removing the DS floor panel) which turns the CDL light on and off. There are a couple of lock nuts to adjust depth.

I would check that the CDL isn't engaged (as discussed above), then adjust the switch. If that doesn't fix the problem then it must be a short in the wiring, however that would be the least likely option.

There could be some play in your t-case which is causing it to flicker on.

[land864]

It has a retrofitted 4 speed ( before me , from a Rangie I think ) with the smaller handbrake drum

[bee utey]

The wires will be hanging loose, earthing out, broken etc. Make a new twin wire harness for the switch and connect it up to the existing harness where it is in good condition.