Important info regarding fuel gauges!

Post by **DanRodd** » Sun Sep 09, 2007 4:31 pm

Hi all,my 2nd post,and here is a piece of very useful info that is not ANYWHERE on the net,and even Bull Motif didnt know about it!
As ive read on here,fuel guages do give a lot of trouble,as did mine,which didnt work.Id replaced the sender,guage,wiring,stabilizer,the lot,and nothing.

I then delved a bit deeper into the situation,and discovered that these voltage stabilizers that go behind the speedo,are polarity specific,and my car had been converted to Negative Earth.As the stabilizer was a positive earth one,it had burnt out and was useless.I fitted one off a 70's Reliant Robin,and it worked perfectly.

Therefore,in addition to the known list of things to do when converting to Negative Earth,change the voltage stabilizer to one off a Negative Earthed car,otherwise yours will burn out.

Hope this may prove useful

Dan

Post by **alex_holden** » Sun Sep 09, 2007 5:20 pm

I know the modern solid state electronic ones are polarised, but I thought the original electromechanical ones didn't care.

Post by **bigginger** » Sun Sep 09, 2007 5:31 pm

Seconded - never had a problem with one.

Post by **aupickup** » Sun Sep 09, 2007 5:54 pm

nor me and i have changed all mine to neg earth

Post by **overider** » Sun Sep 09, 2007 7:30 pm

I have changed my saloon to neg earth with no problems. But I had a problem with the voltage stabilizer on my convertible and changed that for a solid state one and that was defiantly pole sensitive.

Post by **DanRodd** » Sun Sep 09, 2007 8:45 pm

this was just my personal findings,and i have read on the tinternet on a site all about these stabilizers that they are polarity specific,which would account why both the minor ones were dud and black and burnt on the inside.I will see if i can find the reference source to link to this thread

Post by **bigginger** » Sun Sep 09, 2007 8:57 pm

Good luck - but there are an awful lot of people on here who have switched to negative earth on an awful lot of Minors without having that problem.

Post by **bmcecosse** » Sun Sep 09, 2007 9:08 pm

The originals were simple 'hot wire' bi-metalic units - which are NOT polarity specific - how could they be !

Post by **DanRodd** » Sun Sep 09, 2007 10:36 pm

well,it fixed mine and in any case i bought a modern solid state one for when i fit a temp guage etc

Post by **bmcecosse** » Sun Sep 09, 2007 10:41 pm

Use a mechanical temp gauge - they work!

Post by **DanRodd** » Sun Sep 09, 2007 10:45 pm

what exactly do you mean by a mechanical one?ive got a selection of Smiths gauges to fit,was just going to fit the sender in the head,and the normal type guage in the dash.Also regarding my original post,i do apologise if its all a load of rubbish,but its the thought that counts!
in that case then,there must be some dodgy info on the net,but it provided an answer to my problem so you can understand why i thought it would be correct.

Post by **bigginger** » Sun Sep 09, 2007 11:38 pm

DanRodd wrote:Also regarding my original post,i do apologise if its all a load of rubbish,but its the thought that counts!
in that case then,there must be some dodgy info on the net,but it provided an answer to my problem so you can understand why i thought it would be correct.

Not a problem - we all write some garbage every so often, me specially

Just trying to correct it in case anyone reads it and thinks that it IS a problem...

Post by **Kevin** » Mon Sep 10, 2007 2:41 pm

what exactly do you mean by a mechanical one?

One with pipework rather than wiring like the ones used on MG`s.
As Andrew says no need to apologise you cant all attain my levels of perfection
1 hour = 1 mistake

1 Year = ...............

Post by **bmcecosse** » Mon Sep 10, 2007 9:23 pm

Mechanical temperature gauge (not guage) has a long slim tube filled with ether, connected to a bulb unit that fits in the head (or wherever there is a tapping - sometimes in the thermostat cover) and these tend to be much more accurate but of course are also quite fragile !!

Post by **ColinP** » Wed Sep 12, 2007 3:28 pm

Mechanical temperature gauge (not guage) has a long slim tube filled with ether, connected to a bulb unit that fits in the head

Silly me - I thought that they just screwed into the top of the radiator so the dial stuck up above the bonnet....

(or was that the other minor?)

Colin

Post by **bmcecosse** » Wed Sep 12, 2007 9:29 pm

I just tend to use the radiator overflow pipe - if steam coming out - it's overheating. Gauge on bonnet would work - may make closing the bonnet a tad difficult.

Post by **pmdavies** » Thu Sep 13, 2007 2:00 pm

Well I've learnt something today as I've never heard of a fuel gauge voltage stabiliser. Out of curiosity does anyone know exactly what it does and how it works. I'm guessing it evens out the peaks and troughs from the sender unit to stop the needle moving all over the place??

Post by **Stig** » Thu Sep 13, 2007 3:29 pm

Ah, no. The fact that the gauge is based on the heating of a bit of bi-metal rather than electromagnetics/electronics is what evens out the peaks & troughs from the sender unit.

The voltage stabiliser is there to feed the gauge with a constant 10V rather than the 12V to 14V you get on the battery. Otherwise it would read higher when the battery's charging than at idle.

Post by **bigginger** » Thu Sep 13, 2007 3:47 pm

Stig28 wrote:Ah, no. The fact that the gauge is based on the heating of a bit of bi-metal .

The stabiliser, surely? The gauge is operated by a variable resistor at the sender end, isn't it?

Post by **Stig** » Thu Sep 13, 2007 4:18 pm

bigginger wrote: The stabiliser, surely? The gauge is operated by a variable resistor at the sender end, isn't it?

I think both the gauge and stabiliser are thermal. With the gauge it is indeedy operated by the variable resistor in the sender and this allows more or less current to flow which heats up the bimetal by, erm, more or less and hence the pointer reads more or less.

To be honest though this is just from memory, I've not pulled a gauge apart to check.