Thread: negative ground temp guage into positive ground car?

Originally Posted by mfc

can it be done? ie into an older series..... im having no luck even wiring it in . do i have to go to a mechanical guage?

I think you would have to insulate the body of the gauge from the body of the car (if that's at "ground" potential- ie +ve) and connect it to the "live" (negative) wire from the sensor, and connect the sensor input to the bodywork. I am assuming that the gauge works by sensing changes in resistance with temperature of the sensor, but I could be completely wrong...the thing might end up working backwazrds...

Coop

Originally Posted by C00P

I think you would have to insulate the body of the gauge from the body of the car (if that's at "ground" potential- ie +ve) and connect it to the "live" (negative) wire from the sensor, and connect the sensor input to the bodywork. I am assuming that the gauge works by sensing changes in resistance with temperature of the sensor, but I could be completely wrong...the thing might end up working backwazrds...

Coop

I've been trying to nut this out myself, because the gauge has two studs, not three. In normal operations, two of the studs are connected to positive and negative (reference voltage), and the third stud is grounded through a variable resistance (sender). I have a feeling that you might have to mess around with the guts of the sender to get it to work.

Why not just convert the vehicle to +ve earth and get it over and done with ?

There's nothing in a series Landy that is polarity conscious. The generator needs to be re-polarised. ie. disconnect the field winding on the generator, swap the battery around and tap the lead onto the field of the generator so that it becomes 'negative earth' and 'Bobs your uncle'.

If by chance your Landy has been fitted eith a +ve earth alternator, just toss it and replace it with a negative earth one and all's good.

Back in my poor apprentice days I had a series II +ve earth Landy and a Ford XM ute (-ve earth) but only one generstor. 15 minute change over of generator from one to the other including 're-polarising' and good to go. Became an expert at it. Ultimately bought a second generator but in those days 'lifestyle' had a higher priority...............


Deano

I think he might have to swap the coil primary over too. Not essential but I think coils are set up to have the spark jump from the hotter negative centre electrode.
Could make a difference to proceeding or not when the chips are on the table - cold, wet night, battery old.......

Terry

worked it out.... the sender needed to be earthed{in a normal car it is through block} .....
1/ so put youre positive wire from gauge to a negative wire or neg terminal.....
2/put a large wire eye thingie under the thermostat and run that to negative
3/earth youre earth wire as usual to a chasis point
4/ sender wire as usual

it works on my 86 inch when wired to battery,so ill let you know how it goes with the power coming through the loom
{this sender has insulation seperating the thread from the sender body}
cheers mark

Mark,

I found this Smiths installation instructions among my files, might be useful.

As far as I understand it the sender is a variable resistor and the gauge is a current measuring device. So wiring it into a pos earth would just drive the needle the wrong way. Swapping the B and T connections (on the Smiths gauge) should make it work? (you still have to earth the sender)

The confusing thing is that I bought this gauge for the Series 1 when it was still pos earth, it has been neg earth with an alternator for some years now and I don't remember if I had to change the wiring to the gauge..

Anyway good luck with it.

Terry

Why not buy a mechanical type temp gauge?