[Healeys] Gas Gauge

Wed Aug 26 12:17:10 MDT 2015

Michael,

I understand your concerns but I do not think you have to worry as the 
capacitor is on the gauge terminals, the voltage remains 12V max. and 
the current is depending on the resistor in the fuel gauge sender and 
gauge itself, both resistors are fairly high so the current will be low 
with not more risk of sparking compared to the original system that can 
theoretically spark as well in the potentiometer of the sender.
The capacitor is just there to reduce the violent differences in voltage 
across the gauge terminals
Anyway a capacitor is supposed to reduce sparking, as with the capacitor 
across the distributor points.

Kees Oudesluijs

Op 26-8-2015 om 18:01 schreef Michael Salter:
> Kees,
> I would have to disagree with your recommendation of adding a 
> capacitor to the circuit to try to stabilize the needle on any fuel 
> gauge system as has been mentioned previously on this list.
> Capacitors are energy storage devices and the sudden discharge of that 
> energy creates sparks.
> A fuel tank is normally filled with a mixture of fuel vapour and air. 
> Certainly the ratio of air to fuel vapour has to be correct for an 
> explosion to occur (around 6% vapour) but, should it be within the 
> correct range which I agree is fairly unlikely, and the capacitor 
> choose to discharge the consequences would be, shall we say, unfortunate.
> Entirely up to you but I certainly don't like the idea and would 
> definitely not recommend it..
>
> Michael S
> BN1 #174
>
> On Wed, Aug 26, 2015 at 7:49 AM, Oudesluys <coudesluijs at chello.nl 
> <mailto:coudesluijs at chello.nl>> wrote:
>
>     If a sender is not working properly it may be that a wrong type is
>     fitted with a float lever rod that is to short, to long or bend in
>     the wrong way. If it is to short the dial will indicate the full
>     range from empty to full while the tank is not full when it reads
>     empty correctly or the other way around. If the lever rod is to
>     long the dial will not read its full scale indicating partially
>     full when full and/or partially full when empty. Lengthening or
>     shortening is a fairly easy operation but needs some experimenting
>     and a dead level floor.
>     Also a bend lever may lead to faulty readings similar to those above.
>
>     On the early coil type gauges you can fit a big capacitor to
>     counteract more or less the continuous restless moving about of
>     the needle which you do not have on the later bi-metal gauges that
>     give a steady reading.
>     Kees Oudesluijs
>
>
>
>     Op 26-8-2015 om 13:27 schreef Michael Salter:
>>     Actually a Healey fuel gauge can be made to work very accurately.
>>     The gauge in my 100 is as steady as a rock and a very accurate
>>     indicator of the tank contents.
>>     The only change I made was to add a tiny connecting link between
>>     the float arm and the body of the gauge sender as in the attached
>>     pic.
>>     Prior to doing this I had no idea that a gauge of this type could
>>     work so well.
>>
>>     Michael S
>>     BN1 #174
>>
>>     On Wed, Aug 26, 2015 at 1:18 AM, John Spaur
>>     <jmsdarch at sbcglobal.net <mailto:jmsdarch at sbcglobal.net>> wrote:
>>
>>         Yes! Will you ever be able to adjust it so it works even
>>         remotely close to
>>         accurate? I don't think so. There are many posts covering
>>         issues with the
>>         fuel gauge and tank unit. My gauge and sender were
>>         "calibrated" by a couple
>>         of shops. The sender is a restored original. Afterwards, it
>>         would still
>>         stick on full, then when over half a tank was used it would
>>         drop to 1/2,
>>         then 1/4 and stop.
>>
>>         I finally calibrated my gauge, with a little more success
>>         than the
>>         professionals, using the calibration unit in this link:
>>         http://mgaguru.com/mgtech/electric/fg_01.htm BTW, I pulled
>>         the sender out of
>>         the car and calibrated it on the bench. You will need to
>>         approximate the
>>         high and low limits which are determined by the depth of the
>>         petrol tank.
>>
>>         Be warned, it still is almost fruitless. I believe the
>>         problem is caused by
>>         how the fuel gauge T and B coils line up with the armature.
>>         The fuel gauge
>>         needle is connected to the armature and swings based on the
>>         magnetic current
>>         supplied by the sending unit. Over the years the coils have
>>         tilted and
>>         cannot be properly aligned with the armature when the nut is
>>         tightened. This
>>         throws off the adjustment.
>>
>>         Let me know how it goes.
>>
>>         Regards,
>>
>>         John Spaur
>>         '62 BT7
>>
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>>
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>>
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