Rear diff lock actuator - no power getting to it.

[Christopher Bell]

I have a 1996 80 series on which the (OEM) rear diff lock stopped working last autumn. I (foolishly) assumed "actuator corroded up" and asked Exeter Gearbox Centre to replace it. They (wisely) did an electrical test first and said "it looks OK, but it isn't getting any power" and handed the problem back to me, so it seems that I have an electrical problem.

That was wet, cold and muddy then and - without a ramp or pit - I couldn't be bothered to crawl underneath and get cold and filthy; but this is warmer and drier now and I need to sort it out.

All the electrics seem to be working OK with centre and front diff locks operating correctly, and the relevant lights flashing / steady on the dash. However the centre light, which goes on first, definitely dims when I select rear, but doesn't dim when I move on to select front + rear, which suggests to me a full or partial short somewhere.

So I imagine I'm looking for a broken wire and/or rubbed through wire shorting out to chassis earth. I have the wiring diagram, but I have no idea where the cables run or - crucially - where they go through the bodywork.

Does anyone have any advice, tips or experience to offer?

Thanks in advance

 

[Rob80vx]

When they checked it for a power supply did they have the center diff locked? The lockers only work with the centre diff locked, and if they checked it without, it would show no power even though the rear diff light is flashing. The rear locker is well known for failing when they corrode and let water in.

 

[Christopher Bell]

Yes they did. It's a manual box, so I disconnected the switch for the CDL on the transfer case and fitted a manual switch to the dash yonks ago.

I forgot to tell them this, and they failed to spot it, so they hot-wired the outlet from the ecu to achieve the same end result. Slight embarrassment on both sides when I pointed this out!

 

[Chris]

It's a tricky one is this. I would like to stick a spare actuator onto the plug and try that - just to prove that it's not the motor. Also the motor only gets power for a couple of seconds. The 4x4 ECU fires the motor momentarily so that the energy is then stored in a spring. If you turned the switch then went to test the power, you'd get nothing even if it was factory perfect.

You can undo the indicator switch from the housing and check that is working too. My old white 80 wouldn't go solid orange on the dash. I though it was stuffed until I tested the ball and plunger only to find that it was locking, but the sender was not telling the ECU.

Are you saying it's not locking because the wheels will go around if you jack it up - or simply because the light says so?

Wiring faults are pretty rare on this system.

Chris

 

[Christopher Bell]

Thanks, that's really useful to know - I didn't realise the power was for a short period only, I assumed it would be continuous until engaged, and I bet that's what they expected too.

I need to break open the wiring connector underneath, obtain a glamorous assistant to work the dash switch and see what registers on a multi-meter.

As you say, given the age of the truck a corroded up actuator seems much more likely. I've just been too much of a wimp to stick my own head under there over the winter.

 

[Chris]

Inside there are two counter wound clock springs. When you fire the motor, the spring winds up and the power stops or else it would basically burst. When everything lines up (which it may do instantly) the clock spring shoots the lock via a pinion on the end of a shaft. When you unlock, the motor fires and winds the other spring. When the load is off the diff, it shoots the pinion the opposite way.
Actually I have never taken a rear on to bits, but several front ones. I have to presume they're the same.

Welcome to the forum by the way.

Chris

 

[Christopher Bell]

I'm a bit nervous about taking it apart. Not only am I lacking in facilities (and skill!) but the FSM talks about having to put some special sealant in there to put it all back together again. That's why I asked the pros to do it.

I can do the electrical checks myself, and I need to do that before proceeding.

THanks for the advice, signing off for this evening - tummy needs routine maintenance...

CB

 

[Rob80vx]

If it was me I would remove the rear actuator its not a big job, then hook it up to the front wiring that you know is working and try it. If it works you can refit the unit and start on the wiring, if it doesn't it can be repaired while its off. I was dreading doing mine but when it came to it it was quite easy.

 

[Justin_Elliott]

I've a '93 80 and have previously suffered with wiring problems at my rear actuator too...

I ended up replacing parts of the wiring loom between the actuator and where it enters the body (near side rear quarter.).

Once you're sure the actuator is working it should be fairly straight forward to trace the wiring back and check for continuity / shorts between the actuator and the next section of loom. I made a short test lead up, and connected the actuator up further up the loom to check it works...

Here's a copy of the wiring diagram and loom location, I've tried to highlight the specific sections of interest; although I can't seem to get Photobucket to accept the Wiring diagram in a readable format... so pm me your e-mail address if you want a readable copy.

The section of interest loom (in red) ends between the chassis / body in the rear quarter into a white and grey plug iirc

Plug R19 - Actuator / R20 - Act Position SW

0

{Edit, I traced mine back to here}

 

[Julian Voelcker]

Hi Chris,

How are things?

The chances are the magnets have come loose in the motor on the actuator. You need to get it off and strip it down.

You should be able to use molegrips to undo the philips screws for the motor cover whilst it is in situ - a round metal cover facing driver's side wheel. Within it there are four magnets - chances are one or more are loose and need sticking back in place.

What ever you do, make sure the magnets go back in order.

You will need some form of RTV/Silicone sealant when you screw the motor cover back on - for ease of access we always use M6 x 12.5mm bolts with spring washers when re-assembling.

Good luck.

 

[Christopher Bell]

Hi Julian

Glad you're still alive & kicking.

The LC80 is still trundling along, exhaust getting a bit smelly in its old age (176k miles now) which suggests that the injectors need doing, the RDL has stopped working as described in the thread above, and the lacquer is peeling off parts of the bonnet which doesn't look very nice, but otherwise no problems. Oh, and it has the standard "slow windows in winter" problem too of course!

It's now shod with BFG all-terrains on all 4 wheels which, so far as I can see, don't wear at all and are brilliant for the sort of use I give it. It saved our bacon - or, more precisely, allowed us to drive out and buy bacon - in the last two snowy winters, and also took us in air-conditioned comfort to the south of France last summer. A versatile piece of kit.

I had a quick look at a 200 series the other day and it's all a bit fancified, and I've come to the conclusion that my ideal car would be my 80 series restored to "as new" condition.

The family is growing up, although our youngest (now 14 & taller than me) was diagnosed with ME two years ago and has missed a lot of school over that time. He is also hobbling around with his foot in a cast at the moment thanks to a driver running a red light at the pelican crossing on the road that divides his school. It was an old bloke who was "a bit confused" according to the Police, which is apposite given the current discussion in the press about older drivers.

We still have 2x horses; they are pensioners now and I haven't trailed them anywhere for ages, but it's nice to know that I can if I need to. In fact they are peering over the fence into my office as I write making "where's our breakfast?" noises, so I'd better go and do something about that.