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Brake warning light

To: 6pack@autox.team.net, klarsen@inreach.com
Subject: Brake warning light
From: DANMAS@aol.com
Date: Fri, 30 Jun 2000 23:22:25 EDT
In a message dated 6/30/2000 10:27:18 PM Eastern Daylight Time, Kendall 
Larsen <klarsen@inreach.com> writes:

>  I've noticed that my brake warning light never comes on? How is this light
>  activated? Is its sensor on top of the brass brake line valve? When is it
>  supposed to come on?


There is a White/black wire going to the PDWA. With the key on, short that 
wire to ground. If the brake light comes on, that part of the circuit is OK. 
If not, your bulb is out or you have a break or bad connection in the wiring 

Since the brake light never comes on, it is safe to say the oil pressure 
light never comes on either, as they are wired in series. Locate the 
white/brown wire going to the oil pressure switch. With the key on, short 
this wire to ground. Do the lights come on (rather dimly, as they are in 
series)? If so, your oil switch is bad. If not, you either have a bad bulb - 
oil OR brake - or you have a break or bad connection in the wiring.

If every thing works as it should, when you turn the key on, but before the 
engine is running enough to have oil pressure, power is applied from the 
ignition key (white wire) to the brake light, and then from the brake light 
to the oil light. The other side of the oil light is grounded through the oil 
pressure switch. As soon as oil pressure is up, the oil switch opens, and 
removes ground from the lights, and they go out.

When the brake sensor actuates (the switch on top of the PDWA), it applies 
ground directly to the brake warning light, lighting it at full brilliance, 
bypassing the oil pressure switch. The brake sensor switch only actuates 
after you've lost one half - front or rear - of your braking system. Often, 
though, bleeding the brakes causes the switch to acuate. When you open a 
bleeder screw to bleed the brakes, the sensor can't tell whether the loss of 
pressure is due to a ruptured line or an open bleed screw. The switch needs 
to be reset sometimes after bleeding. Often, people don't know how to reset 
the switch, so they just remove the bulb to get rid of the annoying light. 
Perhaps a previous owner did this?

Dan Masters,
Alcoa, TN

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