[Healeys] Fuel Probe

Oudesluys coudesluijs at chello.nl
Wed Nov 29 04:19:30 MST 2017

The instruments shown in the picture should be used with a voltage 
stabiliser. All UK cars from the era using Smiths/Jaeger temperature and 
fuel gauges of this type (bi-metal operated, 90 degr. sector window up 
or down) used the 10V stabiliser. It is a small galvanised box about 
15x25mm with two or three blades on a pertinax base: B(attery) and 
I(nstruments). The third one or the body is earth. They were typically 
mounted on one of the speedo-/tachometer or other instrument clamps but 
can be found elsewhere under the dash as well. These instruments are 
sensitive to voltage and the cars system voltage can vary from roughly 
12V-15V, making it impossible for these gauges to indicate a correct 
reading without the stabiliser.
I cannot believe Austin left it out. I very much doubt that bespoke 
gauges of this type not needing a voltage stabiliser were made 
specifically for the A-H 3000.
Earlier gauges without the window were probably used without voltage 
Kees Oudesluijs

Op 29-11-2017 om 11:48 schreef Bob Haskell:
> Kees,
> Austin-Healeys, at least the non-Sprites, did not have a voltage 
> stabilizer.
> Cheers,
> Bob Haskell
> AHCA 3000 MkI registrar
> http://www.ciahc.org/registry_3000mk1.php
> On 11/29/2017 03:29 AM, Oudesluys wrote:
>> The original sender/bi-metal gauge combination of this kind should 
>> work fine and is reasonably accurate. The earlier coil gauge is a 
>> different matter. It does not really give a steady reading. You 
>> cannot mix the sender for the coil gauge with the bi-metal gauge and 
>> v.v.
>> The sender can have the rare fault with earthing or a broken coil but 
>> it is easily replaced. Another often overlooked problem is the 10V 
>> voltage stabiliser that serves the fuel gauge and the temperature 
>> gauge. This is a small metal box usually attached to one of the 
>> instruments. The bi-metal keeps the average voltage at 10V. It is not 
>> very stable but fairly durable. If faulty it can better be replaced 
>> by a solid state device. If both temperature gauge and fuel gauge are 
>> erratic, replace the voltage stabiliser.
>> Kees Oudesluijs
>> Op 28-11-2017 om 22:27 schreef Roger Grace:
>>> For interested listers ...
>>> Ever since I acquired my BJ8 I have been frustrated with the fuel 
>>> sender unit and gauge performance and reliability. Changed out the 
>>> sender 2x and many hours fiddling with gauge adjustment that really 
>>> with the dual attracted armature mechanism is a challenge. The MS 
>>> sender ground strap solution helps if you have a problem with crud 
>>> in the shaft bushes but doesn't help for bad sender coil winding or 
>>> slider contact malfunction.
>>> So. I embarked on a mini science type project to do a full 
>>> replacement with a capacitive electronic fuel probe and a modern 
>>> stepper motor type of gauge. The biggest challenge was getting the 
>>> probe to fit into the original sender unit opening. Our tanks have a 
>>> 6 hole flange and modern cars use a 5 hole SAE bolt pattern and an 
>>> adaptor wasn't feasible. In the end used a probe with 1/8 npt and 
>>> remote electronics. With careful arrangement of the Al mounting 
>>> flange that had to be made, was able to get the probe to also 
>>> measure the fuel in the small well at the bottom of the tank before 
>>> recording E. Next time would do slightly differently to account for 
>>> the dead zone at top of the tank that caught me out.
>>> I had a Smiths look alike gauge built but with a modern 5V stepper 
>>> motor drive. After numerous hiccups along the way, have now got it 
>>> working satisfactorily ... after spending far too much time (and $) 
>>> on it as well ! Will verify final accuracy on the road next Spring !
>>> See a few pix; if anyone wants more details - contact me directly.
>>> gauges are: original/new sm/aftermarket sm cheepo for testing
>>> rg
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