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Re: Smith fuel gauge goes by rev

PostPosted: Thu Mar 08, 2018 5:20 pm
by billwill
umbyfer wrote:
billwill wrote:
smithsdiagram.jpg and


is the diagram for plus 2? not for S4/Sprint...


It is a general diagram for Smiths instruments in ANY classic car. Particular cars will have small variations from this diagram

Re: Smith fuel gauge goes by rev

PostPosted: Thu Mar 08, 2018 5:30 pm
by ericbushby
Umberto,
I do not know a specific supplier as I repaired mine. Someone else will know, or just try your usual Elan parts supplier.
Eric

Re: Smith fuel gauge goes by rev

PostPosted: Thu Mar 08, 2018 6:13 pm
by umbyfer
ericbushby wrote:Umberto,
I do not know a specific supplier as I repaired mine. Someone else will know, or just try your usual Elan parts supplier.
Eric

How did you repaired yours?? i may repair mine...

Re: Smith fuel gauge goes by rev

PostPosted: Thu Mar 08, 2018 10:46 pm
by ericbushby
Well I will try,
First carefully pry open the can and remove the contents.
Fit a 7810 voltage regulator chip with one screw through its heat sink. The `10` is the output voltage.
Connect two 0.1uf capacitors from each outer pin to the centre pin and connect the pins to the wiring tags on the case.
The capacitors need to be tantalum type and about 25 to 35 voltage rating in order to be small enough to fit.

It is a few years since I did this and I have no notes or drawings. You should be able to find which pin is input
and output with a search and apart from being quite small and a tight fit, it is not difficult.

If there is anything wrong with my description I hope someone will put me right. I know John Clegg made several of these and he is never far away.
best of luck
Eric

Re: Smith fuel gauge goes by rev

PostPosted: Fri Mar 09, 2018 10:24 am
by umbyfer
bero starting to replace the voltage stabilizer i found that situatione in my car:
1. original Smith stabilizer is not fixed by the case to the speedmeter case, so not grounded
2. for that reason it is free and "TOP" position is not respected.
3. i don't understand the black wire from "B" (battery 12 V) to ground by condenser

See the pictures where i also assume that mine is original becouse marked Smith part number BR1307/00

Before replacing by a new static one i will check it again if it works or not.

Re: Smith fuel gauge goes by rev

PostPosted: Fri Mar 09, 2018 11:04 am
by Craven
To the best of my knowledge, 3 connections are needed for the regulator to operate.
Input to the device B, battery.
Output to the gauge +
Case to negative or chassis or earthed instrument case.
Capacitor connection is probably noise suppression when radio fitted.
Perhaps the regulator just needs its case connected up.

Re: Smith fuel gauge goes by rev

PostPosted: Fri Mar 09, 2018 11:12 am
by umbyfer
Craven wrote:To the best of my knowledge, 3 connections are needed for the regulator to operate.
Input to the device B, battery.
Output to the gauge +
Case to negative or chassis or earthed instrument case.
Capacitor connection is probably noise suppression when radio fitted.
Perhaps the regulator just needs its case connected up.


I double checked the regulator connected to a battery and keeping in the right "TOP" position; by multi-meter instrument i found that the exit Volt at "I" pin move continusly in a range of volt between 0,6-12V. When it arrives around 11-12 Volt it goes down to 0,7-0,8 than goes up to 10-11-12 and down again.

Re: Smith fuel gauge goes by rev

PostPosted: Fri Mar 09, 2018 11:20 am
by Craven
It?s a switching device, the output is an integration of pulses, you need to connect the gauge and check.