[Healeys] Fuel Probe

[Roger Grace]

No volt stabiliser in AH3000 and earlier.
BTW the Smith gauge shown on RHS is not a standard unit, but a look alike 
specially built for me with stepper motor mechanism with 5V=F and 0V=E
rg

-----Original Message----- 
From: Oudesluys
Sent: Wednesday, November 29, 2017 3:19 AM
To: Bob Haskell ; healeys at autox.team.net
Subject: Re: [Healeys] Fuel Probe

Bob,
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
stabiliser.
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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>>
>>
>>
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