MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - petrol gauge problems?

Hopefully an eay one that I've missed!

the gauge on my 1964 midget (just back on the raod in time for spridget 50) has always read back to front since its been fitted, in other words when I fill the tank, the gauge reads empty, then as I use the car the gauge climbs up to full - great fun to watch, but not too helpful.

I thought that this may be down to the conversion from positive to negative earth?

The gauge is the one with 3 terminals on the rear and 2 green wires and 1 green/black wire that feed into the gauge.

Any ideas on this?

John
John Collins

I think its a Positive earth gauge, mine did this it reads backwards or not at all, I put a later gauge in and all works OK.
K Harris

John, I have a positive surfeit of -ve earth fuel gauges, would you care to try one?
David Smith

John

Early gauges and sender units work the opposite way to later ones.

You need the correct sender for the gauge.
Dave O'Neill 2

<then as I use the car the gauge climbs up to full - great fun to watch, but not too helpful. >
I had a mismatch like this, E=enough, F= ****-all.
Entertaining yes, but very useful if you run out of petrol in a place where you get fined for doing so!

Paul Walbran

Hi,

thanks for all replies, I too have at least 10 later gauges, but they all have only 2 terminals on them,

do I join the 2 green wires together then? sorry if I seem dim, but I've been doing lots of housework lately (as promised before spridget50) so have not been in the garage as much as i'd have liked!

John
John Collins

As the green wires start in the same place (fusebox isnt it?) I cant see why not. the second green is simply a feed to the "oil filter blocked" lamp if you use it

the circuit runs green from fusebox to gauge then green/black to tank unit then earth on the tank fittings.

(unless like me you have added a voltage stabiliser like the later cars have, if you want to run a stabiliser see me after school next time and I'll show you hwere mine is and how it's wired)

remember that a "colour"/black trace wire is on its way to earth somewhere down the line.
Bill

You can't use the voltage stabiliser with the early gauges as they aren't damped like the later ones.

The VS gives an on/off square-wave voltage, so the early gauge would be constantly flicking back and forth. Very distracting!
Dave O'Neill 2

Dave

dont panic Mr Manner...

I had to use a later gauge (like many of those that I know John has!) so I rewired to allow the use of a stabiliser

Not a difficult job and has since paid off because after my "Calibration Sunday" a couple of years ago I have a rather reliable gauge that actually tells me how much fuel is in the tank

(OK not quite, when it says empty I have twenty five miles to find a garage)

Bill

Thanks for comments, I have fitted a later gauge and it now reads full - because the tank is, so I will have to use the car and see what happens, will be interested to talk to Bill about this, but will have to wait until Sept as I will miss august meeting.

Dave, have you still got the tonneau bars? I hope so and I'll sort out collection when I come off hols on the 12th augs

John
John Collins

I have had this exact same problem since I bought my car. I thought that polarity (+ive/-ive earth) did not affect the fuel gauge as it measured resistance? Is there any way of identifying which gauge is which (early versus late is a bit vague)?
Chris H (1970 Midget 1275)

This thread was discussed between 12/07/2008 and 14/07/2008

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.