Fuel Guages

Cuppa when this happens have you tried using a jumper lead from the aux negative to the cranker's negative?
Even disconnecting the negatives from the aux battery pack might show a difference in the cluster instruments.

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Originally Posted by macca

Cuppa when this happens have you tried using a jumper lead from the aux negative to the cranker's negative?
Even disconnecting the negatives from the aux battery pack might show a difference in the cluster instruments.

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No I haven't tried it Macca, but that is essentially what I meant by use of a switch. Disconnecting the aux negative might be a bit impractical as I have several earths to the pod, & one main earth from pod to chassis (which is switched & only switched on to parallel the aux batts with the crank). Disconnecting the earths to pod could be done, but not conveniently. It is possible that those earths have continuity to the chassis via the pod mounting bolts, even though the pod is now mounted on rubber pads. When the problem occurs I'll firstly try paralleling the aux batts with the crank. If that has no effect I,ll try running another earth wire direct from aux to the neg terminal of the crank ....... But if that were to work I still would have no idea why.

Cuppa

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Originally Posted by Cuppa

Any chance you might draw a wiring diagram of your full charging setup & post it or PM it to me? This intrigues me. My aux batteries are earthed similarly, to the aluminium pod, & from the pod to the chassis via a tray mounting point too, but I can't for the life of me understand how this could have any effect on the instrument cluster. My aux batteries are charged via a dc to dc charger & by solar. Essentially the two battery systems are separate. I can't see how using the chassis as a common earth would have any effect, let alone how providing a further direct negative connection between the two batteries could help.
I don't doubt that your problem was fixed, but I would like to understand exactly how, if that extra earth is responsible.
Any chance that whilst the work was being done that any other connections may have been disturbed?
And what size wire did they run back to the block? I'm tempted to run the extra earth like you have, but with an inline switch so I can run as is, & when the fuel gauge problem occurs, flick the switch & see if it immediately comes good.

I might wait to see if this solution works for Rafa.
I can't remember if the gauge problem on my vehicle preceded the installation of my aux batteries or not.

Cuppa

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Hi Cuppa,

The chassis on the Patrols is not earthed. If you have a look at the main battery the negative cable connects to the body (just under the battery) and to the engine.

The fuel sender units mounted in the fuel tanks have a small gauge earth wire running to the senders, the design of the the sender unit when bolted in the tank and the tank bolted to the chassis rail supplies a small earth to the chassis. This earth wire is small and can only just handle the circuit for the fuel gauges. In the early Patrols it couldn't even handle this, there were all sorts of problems with the sub tank transfer and the fix was to run an earth lead to the chassis.

When accessories or other batteries are added to the vehicle and use the original earth circuit this can very easily overload it and cause all sorts of problem. The body of the vehicle should not be used as an earth for high current drawing accessories, the chassis can be used but you will also need to run an earth lead from you battery/batteries to the chassis.

Your solar panel shouldn't cause any problems. The DC-DC is not a generator it still relies on the alternator. Where is the DC-DC charger mounted?

Cheers Rodney

Hi Rodney,

BCDC1240 is mounted in the pod.

I have sent you a PM.

Cuppa

Hi Cuppa

I'll draw and scan basic plan and check size of wire tonight and post it tomorrow.

At the time there were all sorts of theories from various people and experts around here and down in Brisvagas but in the end, the earth fixed the problem.

cheers

Hi Wiz, no need now mate, thanks. Yendor has explained the problem, & his suggested solution having looked at a wiring diagram of my set up is to try adding a further earth cable between the neg terminal of the crank battery & the chassis. I am optimistic that this will fix the problem. I had not considered a) that the chassis itself is not earthed directly on Patrols ( had tested continuity, but this doesn't tell capacity, only connection & b) that it is possible to overload an earth. If this solution doesn't work for me, then the problem will most likely lay within the instrument cluster, but as I say, I'm optimistic that this will fix the issue.

Others have previously said 'earthing problem' but I hadn't really understood just what that might mean until Yendor,s post.
Anyone else with the problem should try the simple adding an extra earth direct to chassis. I think your additional earth would have achieved the same outcome, but easier to run the earth from crank battery to chassis, rather than, in my case, another wire from inside the pod to under the bonnet.

Cuppa

Good luck Cuppa hope it works

When my auto elec upgraded the earth to to third battery in the pod the gauges went back to being ok.

:)

Might have mentioned it on another thread but Tojos earth out sections of the 4x4. EG;;;; headlight, engine bay, dash ,front cabin, rear cabin ,cargo and rear bar.
With Nissan I don't think one earth could do the whole 4x4, I'll be running extra earths over the next few weeks

This was posted on the other Patrol forum. It was taken from a Nissan Learning Manual.

Those guys that are also having trouble with their keyless entry not working correctly may also want to try adding this earth.

Cheers Rodney