It works like this: Before you actually start the car, and the oil
pressure switch
is closed, both lights light up dimly, because they are in series and each
get only 6 volts. This is obviously for verifying that the bulbs are not
burned out.
If you have a brake failure, you will notice it first when the car stops
poorly or
not at all. Some time later, you will notice that the brake light is
glowing brightly.
If you have a loss of oil pressure, both lights will glow dimly, and if it is
not daytime, you will hopefully notice this.
If you have a simultaneous loss of oil pressure and braking, the
brake light will go on, but not the oil light.
If either lamp burns out or gets a bad connection, neither will glow
when you start the car or lose oil pressure.
Sound totally lame? I think so. The correct solution would have been to add
a couple of diodes to the circuit so that the oil pressure switch turned on
both lamps with a full 12 volts, and the brake switch turned on the brake lamp.
But they were too cheap.
On my car, I have disconnected the brake pressure switch (aka PDWA)
because it is useless, and stuck a shorted-out bulb in the brake lamp socket.
Now, at least the oil lamp works like it ought to, and I haven't had to
cut any wires...
Doug Braun
'72 Spit
At 12:21 PM 3/7/00 -0800, Ken C wrote:
>Spitlisters,
>
>Some confusion on my part regarding the wiring for the oil light on my '72
>Spit.
>
>The sender is just a pressure activated switch, normally closed, (light on),
>until oil pressure turns it off, (light goes out). Looking at the wiring
>diagram, it appears the oil light is wired in series with the brake light.
>My assumption is that both will come on when the ignition is turned on, then
>go out once oil pressure is obtained. But won't both lights come on if there
>is a loss of oil pressure ? And with a brake failure, (or brake switch
>failure), the oil light will never come on. Or am I looking at the diagram
>crooked ?
>
>Maybe it's time for a gauge.
>
>Thanks...Ken C
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