The Voltage Stabilizer has a resistance element which draws current and
drops the voltage as seen by the Temperature and Fuel senders. The current
flowing through it heats it which, in turn, heats the bimetallic contact
which is gradually bent until it shorts out the resistance element. Without
current flowing through it, the element cools and allows the bimetallic
contact to cool and spring back which removes the short and allows current
to flow again and the cycle repeats itself. See diagram below
+-----------------------+ <--- bimetallic contact
| |
V |
IN O-----T--/\/\/\/\/\/\/\/\-----+-------O OUT
^
|-- Resistance element
The way to test it is to put it in series with resistance to simulate the
senders and gauges (probably several hundred ohms, I've never measured them.)
and apply 14 volts. See diagram below. Measure the voltage across the load
resistance and see if it is approximately 10 volts for a range of load
resistance (50% to 200% of the starting value). When I get back from my
business trip, I will measure the gauges in my Spitfire for more specifics.
+--------------------------+
| |
--+-- |
--- +---+
----- <-- 14 Volt Source | | <-- Voltage Stabilizer
--- | |
----- Load resistance | |
-+- | +---+
| V |
+------/\/\/\/\/\/\/\------+
Regards, John Pratchios, '80 Spitfire
______________________________ Reply Separator _________________________________
Subject: Re: Fuel gauge problems
Author: "A.D.Smith" <A.D.Smith@boris.umds.ac.uk> at smtp
Date: 10/31/95 4:33 AM
Hello all,
well I've got lots of suggestions to try there. The one that I
think is most likely (or at least the one that I want to be true) is that
the problem lies with the "Bimetalic voltage stabilizer" in series with the
gauge / sender. The funnt thing is that I replaced this about a year ago !
My understanding is that it's some kind of capacitor.
So todays question :
Does anyone know exactly what's in there, so that I can bring it
to work and get the electronics guys to test it ?
I know they're cheap, but I'd just like to understand what goes on in there.
It's a '77 midget, and this thing is a two pronged little Lucas box, about
1/2 inch by and inch, in line between the fuel gauge sender and the gauge
itself. Its purpose I think is simply to damp the swings from the sender
unit as it bounces around in the tank.
[SNIP]
Andy
|