Wiring diagram for 6x6

[Acco6x6]

I  have been trying to follow the 4x4 diagram but it does not show the tachometer wire so  I am wondering if there is one for the 6x6 out there

          Cheers
          Stewart

[Ravvin]

I've never found one, but I can have a look under the dash on mine tomorrow if you like.
I suspect there will be a single wire to the gauge that runs to the alternator.
I'll get the number off it for you, if you like. Mine works.
I have to sort out the temp gauge at some point. At the moment, the dash is only held down with 2 bolts, so it's no trouble.

Greg.

[Acco6x6]

     Thanks Greg that would be a great help.  Something has happened while I have been fiddling around to make all the gauges stop working

[Ravvin]

Oh that is probably an earthing issue.
I plan on running a wire from somewhere on the back of the panel to a good earthing point on the chassis.
All of the gauges and lights rely on the contact between the front panel and the frame for an earth. I hadn't realised this and was wondering why nothing worked when I had the panel off.
A quick check with a multimeter between the front panel and the intake manifold or other good solid earthing point will tell you if its earthed properly. Should be low to no resistance.
You should be able to run a wire down and through a grommet in the panel next to your left knee. From memory, there should be a couple of bolts through the chassis rail directly below that you could use to connect to. 5/16" UNF nut should fit.
The cab has a really poor electrical connection to the chassis and engine. It would actually pay to run a few good earth straps from the chassis to the cab, as the originals are probably broken or missing totally.

Greg.

[Acco 4x4]

Hi all, sorry been awake for days so forgive me if I've missed something here.... but wouldn't the wire for the taco go to the points wire on the coil?

[Ravvin]

Could be. And would make sense as the earlier trucks had generators, not alternators, so nothing to connect to on the back. I was thinking too modern, as I've recently had issues with the work ute's tacho and it was a bad connection on the alternator.
I'll check the number on the wire n the gauge tomorrow and see if I can find a matching one near the coil and distributor.
Should be easy. It'll be a yellow one. 😆

Greg.

[Ravvin]

Ok, quick update before my assistant arrives.

On the back of the tacho, you have 4 wires. One is just the lamp. 2 wires, both marked as 27, are the earths. They link to other gauges on the panel.
The last wire is either 66 or 99. Can't tell.

On the coil, you have a single yellow wire on one side, labelled 12, I think. Hard to tell as the oil/grease on it removed most of the old writing when I wiped it clean.
On the other side of the coil are 3 wires. The single black one goes down and into the side of the distributor.
The 2 yellow wires on the same side are labelled as 88 and 66 (or 99), so this is your tacho pickup.

Hope that helps.

Greg.

[Acco6x6]

   Yep got you guys  the tachometer wires are from the coil.  Still having trouble getting power to the oil and temp gauge   Looking at the wiring diagram I think the pickup is off the ignition switch but for some reason not to the gauges.  I am wondering which relay protects them if they short Is it the ignition one or another somewhere? As yet I have not checked at the plug under the bonnet and have not run the earth off the motor or somewhere decent as Greg has suggested, only from a stud which holds the dash panel on

      Stewart

[Ravvin]

My oil pressure sender and gauge work, but not my water temp gauge.
I tried taking the wire off the sender, up on the driver's side of the head, just above the intake/exhaust ports, and shorted it to the block, but the needle never twitched.
When I get a chance I will check that I have power to the gauge, and if so, I'll short the other wire to ground and see if the gauge moves.
I'd say it's been this way a long time, as someone has fitted a VDO gauge up near the air cleaner warning thing.
So much to do, deciding where to start is the issue.

Greg.

[Acco 4x4]

Hey
Just checked the wiring manual and the coil wire is labeld 99. It runs from the coil to the tacho via a couple of cable plugs. As for the temp, oil pressure and fuel gauges, these are all the bi metal type. Generally you have two wires (excluding lighting) one (usually positive) switched power to the gauge and the other an earth which runs to a sender. The sender varies resistance (full to empty, hot to cold and low to high) which changes the voltage through the bi metal strip in the gauge, these changes the temperature of the strip and it deflects and moves the needle. Anyway, with the gauge senders, make sure they all have good clean contact and the wires are in good condition. Poor connections etc will result in high resistance and an inaccurate gauge indication. To test the gauges, check for power with a test light or similar at the gauge. If you have 12v at the gauge, try earthing the sender wire, this will make the gauge move completely to either side depending on how it is set up, generally default to worst case scenario, no oil pressure, no fuel and a hot engine. Although i haven't checked the power wires should all join together and run to the ignition switch, possibly through a fuse but doubt it. See how you go, good luck.

[Acco6x6]

     Thanks for the help so far.  The problem with the gauges was a broken wire 12v near the terminal block in the centre above the windscreen  Now onto the tachometer.  There is wire from negative to diistributor On the positive side there a yellow wire and an extra someone has run to an electric fuel pump there are 2 yellow wires disconnected which must as Greg says goes to the other side which is neg.  Standby !!

[Acco6x6]

    Later today I found the problem.  The wire for the coil had been put on the earth post on the tachometer once I moved it to the next post along I was able to connect the 2 yellow wires to the distributor side of coil and all was good.  I would love to see a wiring diagram for these trucks even if it is only the tachometer I wonder where they are?   
     Many thanks for the help

       Stewart

[Acco 4x4]

Good news! Good to hear your making headway...... I have the wiring diagram which is the same one available to download for the 4x4 which i can't imagine would differ much if at all just for a scone rear axle..... Keep in mind that the trucks were mostly POSITIVE EARTH from the factory and have mostly all been reversed to a more common NEGATIVE EARTH. Depending on who converted the vehicle will obviously determine how the mods were done so there may be some minor differences between vehicles..

[Ravvin]

Good work getting the wiring sorted.

The big difference in the diagrams, as has been shown here, is that there's no wiring shown at all, for a tacho on the MK3 diagram.
The only wires shown going to the coil are marked 12 and 80. Our 6x6's get a 12, 88 & 99.

Another difference is that the MK3 diagram has a generator and the later MK4 and our 6x6's has an alternator. I haven't had a good look at the alternator yet, as it's working, so I don't know if there are wiring differences. I know I still have an external voltage regulator up behind my head, and the charging current must run through the ammeter on the dash at some point, but there's nothing explaining where things run or join.

Hopefully someone will pop in at some time and point us to a better diagram. Or a workshop manual for the F1/2/5. That would be great, as the workshop manual for the MK3 that we have is really useful, but a lot of the parts on our 6x6's are not in it.
One day.

[Bluebell One-eight]

A very interesting discussion. The Army was VERY particular about mods... they were covered by Electrical and Mechanical Engineering Instructions ( EMEIs), the site with the manuals has EMEIs as well . The mods had to be done according to laid down procedure and the instructions included the parts necessary (if any ) and how it was done. The problems here would be post service. The trucks that had generators ( Mk3s)  were manufactured with POSITIVE earth and those with alternators were NEGATIVE. The conversion of the positive earth trucks was necessary to avoid a big SPLATSKI when slave starting. That's why the warning sign was stenciled on the engine cover. If a slave lead was used between two trucks of opposite polarity the lead would effectively short out two batteries in series and the lead could be welded in the socket. The minor instruments (fuel, oil & temp. ) are run from a regulated voltage of about 7 or 8 volts to prevent errors that occur when the battery voltage varies. This is behind the instrument panel in most trucks. If those instruments don't work or show high readings then check the supply voltage first.