Thread: Auxiliary instrument wiring?

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Oh bugger, no responses, looks like I'll have to break out the multimeter and get poking about behind the dash! I've been trawling the internet for an S3 wiring diagram that incorporates the auxiliary gauges, and haven't been able to find one, which surprises me, normally after burning a few hours surfing something pops up! Bugger that red wire!

This might help

LAND ROVER MANUALS DOWNLOAD

Unfurtunatly, no, nothing about the auxiliary wiring there...

The only red wire should be from the light switch to the front park lights. It seems your wiring is not standard. I completely rewired mine a few months ago. Pm sent!

Originally Posted by TJWA

The only red wire should be from the light switch to the front park lights. It seems your wiring is not standard. I completely rewired mine a few months ago. Pm sent!

Thanks for the linked files, unfortunately they do not contain the wiring for the auxiliary gauges, that has really been my problem all along - that there are no Land Rover wiring diagrams for the optional extra gauges - as far as I am aware they were offered as optional extras and fitted by Land Rover before delivery, which makes it odd that there appear to be no wiring diagrams that show these optional extras. They appear in the 'Optional Parts Catalogue', along with the part number for the extension to the wiring loom... but no actual wiring diagram has them on it.

Originally Posted by TeZZaP

Thanks for the linked files, unfortunately they do not contain the wiring for the auxiliary gauges, that has really been my problem all along - that there are no Land Rover wiring diagrams for the optional extra gauges - as far as I am aware they were offered as optional extras and fitted by Land Rover before delivery, which makes it odd that there appear to be no wiring diagrams that show these optional extras. They appear in the 'Optional Parts Catalogue', along with the part number for the extension to the wiring loom... but no actual wiring diagram has them on it.

Ok, an oil pressure gauge would simply have a single wire coming from the sender in the engine bay to one side of the gauge, this acts as the negative. The other positive wire would come from the voltage stabiliser so that fluctuations in voltage would not change the readings on the gauge. The positive could and quite often just be any positive wire that is activated once the ignition key is in the "on" position.

The amperage gauge would have one single wire coming from the alternator, this acts as a negative. The other positive wire would come from the voltage stabiliser, but once again may not need too.

Any gauge is just a voltage indicator that has had a new scale printed on the front to represent the medium it is measuring. Instead of having a light bulb that gets brighter with more voltage difference, you get a needle that moves along a scale, the two devices are connected the same way.

The standard ignition warning light would be wired basically the same as an amperage gauge, the standard oil pressure warning light the same as an oil pressure gauge. The only difference being that they may have their positive supplies from a voltage stabiliser to stabilise the reading on the gauge, and that an oil gauge would be wired to a variable output sender on the engine rather than a pressure switch.

Originally Posted by TeZZaP

Short version: red cable runs from amp gauge to oil gauge and then is supposed to attach to ???

You must have disturbed an ignition positive wire when you had the dash open. This makes me think that there is some non-standard wiring in there as what you did should not have stopped the engine from starting!
I'd say the red wire connects to the "ignition on" terminal of the ignition switch (terminal 2) and that when you pulled it you may have disturbed a piggyback connection that went to your igintion coil or fuel pump.

I am not an auto electrician, I'm an industrial instrumentation technician, so my understanding of automotive electricals is not 100% as my knowledge is industrially based. You may get better information from an auto electrician, there are some very experienced people who frequent the "Technical Chatter" forum and have enlightened me before!

As far as I know the heavy red wire from the amp meter should run from the amp meter to the battery and the othe wire (red?) to the alternator to show chargeing or dichargeing amps I have know idea why it would go to the oil gauge mine has one other wire very light connected to the dash light switch

Thanks for this info, I'm pretty sure that armed with this info and my trusty multimeter I should be able to track down whats wrong now, Thanks heaps.

I've been mussing and it appears to me that just that red wire be disconnected should not be enough to kill all the power... I must have stuffed something else whilst in the dash area... I'll investigate (hopefully later today or tomorrow) and report back