Changing polarity question

[Jindivik]

Hello from Australia,

I am assisting with a project car it’s a 59 Morris 1000 that is having a Datsun engine installed in the process the car is being converted to Neg earth. Everything is working fine except the fuel gauge. The gauge has two wires battery pos and sender. Should it still work with the change of polarity? What it is doing is that with the sender wire earthed it energised but does not deflect. The odd thing is if you turn the gauge up side down and the needle goes to full and you power it up it then deflects. What’s going on here, any help would be great. 

 

[Geoff1946]

Have you tried reversing the wires on the gauge?

 

[Murdoch]

Not sure I can help you buy have you tried contacting these people?

https://www.mmoc.org.uk/

.  

 

[Jindivik]

Yes I have, you get the same result, the the gauge energise you see a very small deflection, this is the same swapping wires across, but if you invert the gauge and the needle swings across, when you power it up it goes full deflection also does this if you swap the wires across. I’m really at a loss to what is going on here……

 

[kerching]

As @Murdochsays.  Contact the Moggy owners club

petrol

electric

wiring

wrong

can result in a whooooooompfph. And a lot of tears

 

[Sidney]

Morris wiring was never brilliant, Joseph Lucas is often referred to as the Lord of Darkness...

On a serious note it may need stripping down and the coils looking at.

 

[kerching]

Joseph Lucas was well known for putting a little bit of smoke inside all his electrical components. The trick is in keeping the smoke INSIDE, once it comes out you are Starmered

 

[Sharpend]

Joseph Lucas was well known for putting a little bit of smoke inside all his electrical components. The trick is in keeping the smoke INSIDE, once it comes out you are Starmered

interesting choice of words as usual Kerching 

starmered - don’t think I’ve come across this one before???

 

[kerching]

starmered - don’t think I’ve come across this one before???

Starmered v.  Past  tense of the verb, to Starmer ....to render useless, to ruin, to knacker, to courgette

derived from the foppish haired , band wagon jumper, "it would have been better if I had done it! Well except local elections obviously, " ponce leading the Labour Party. Face like a slapped arse

quote..."well M'lady, if we do not call the local fire brigade soon the entire thatched roof will be well and truly Starmered. I fear that your spitting on the flames will have little or no effect!...may I proceed?"

from 'Lady Cynthia and the missing members of Trumpton' by Barbara Carthorse

 

[Sharpend]

I’ll add it to the dictionary   

 

[Geoff1946]

To come back to the original query, it does appear to me likely that the indicator itself is probably at fault.

From my recollection of my bangers, sorry classic cars, these fuel gauges were very "low tech." 

The tank sender is a potentiometer moved by a cork on an arm a bit like a ball valve. 

The indicator was either thermal or moving iron meter style. The more sophisticated ones used a voltage regulator, but I think that was thermal/mechanical. 

Nothing I can recall that was polarity sensitive.

Hence I suspect it's demise during you present work is down to co-incidence, or sods law if you like.

 

[kerching]

Isn't there a voltage regulator on the bulkhead of a Moggy thou?

if so, the lack of this on the new build may be a factor....equally it may not