There seems to be a little confusion about the voltage stablizer and its
properties.
1) Yes, it is a bimetallic strip which shorts between "ground" (actually
a resistive load) when cool and passes incoming voltage when warm. Think
of those blinky Christmas lights.
2) Because of this the output is NOT steady. It is SUPPOSED to oscillate
between about 5 volts and incoming voltage.
3) So why don't your fuel gauge and temp gauge needles swing in time to the
stabilizer? Because they are "heavily damped".
In the case of these two gauges, the damping is thermal in nature.
Incoming voltage (determined by supply voltage and the resistance of the
fuel sender or temperature sender respectively) heats a resistive wire,
like the ones in your toaster but cooler. This heat bends a bimetallic
strip, which moves the indicator needle!
Since the normal chopping frequency of the stabilizer is on the order of
1 Hz, the bimetallic strip in each gauge does not have time to cool off
and move the needle between the low and high points of the voltage cycle.
NOW, here is the really ingenious part. Given that you have bimetallic
gauges, what can cause inaccuracy? Bad sender, bad ground, improper
input voltage, and >changes in ambient temperature<. That's right, if
the temperature around the gauge is high, the indicator reading will be
high. And cool temperatures lead to an opposite effect.
Well, now. The bimetallic "voltage stabilizer" has the same "problem".
If the temperature around the stablizer is high, it takes longer to cool
off and break the "ground" phase. This means more time spent at "5
volts" and less at "13.8 volts".
If the voltage stabilizer is exposed to the same ambient temperature as
the gauges, it will tend to compensate for ambient temperature changes
around the gauges!
I think because of this, a solid state voltage regulator would be a >bad<
idea for these gauges.
As for problems, the most common is a missing ground on the stablizer.
This causes 100% 13.8 volts to be passed to the fuel and temperature
gauges, and BOTH will read high.
If one gauge is acting up and the other isn't, the problem is not likely
to be in your stabilizer.
John M. Trindle | jtrindle@tsquare.com | Tidewater Sports Car Club
'73 MGB DSP | '69 Spitfire E Stock | '88 RX-7 C Stock
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