Date: Sun, 25 Nov 2001 11:03:01 -0000
From: "SimonJ" <>
Subject: Re: 1985 900S, 8 valve. Want schematic

"Neal L. Grotenstein" <> wrote in message > Hi > Stick shift car > Back-up light works, brake light does not. > I bought a Haynes Manual, #84010 > > THe schematic of Figure 13.51 shows +12 feeding the (normally > open)brake light switch, then on to the brake lights. THe other side of > the brake lights are grounded. THat sounds logical. > > Back to the car: > This will sound weird.. Everything was measured with a voltmeter and an > ohmeter. I'm an electrical engineer. Lots of analog design before s/w > converted us all. > The brake switch on the brake pedal is normally closed. THat switch > also has a vacuum line. Can't tell where it goes. > There is an identical switch on the clutch pedal both SAAB p/n 951-2294. > I can't see where the vacuun hose from it goes either. Of course, the > switch contacts are also normally closed. Thus both switches show no > resistance when their pedals are not pushed in, and no current flow when > when they are pushed. > THey are wired in SERIES, so that one is wired to the next. As in > brake switch clutch switch > > ------x___x---------------x___x---------- > - ----> 2 pin to 2 --> > --------------------------------------------> plug pin socket --> > > With the plug in the socket and the engne running, the 2 pin socket > is shorted out, and 0 volts & 0 amps( <1 ma) are read. > With everything off, and the plug removed from the socket, there are > 1,530 ohms across the 2 socket pins. > > I realize this sounds weird > THat is what is there. > Comments? > Does not sound weird, sounds like you found the cruise control switches! They work by breaking the curciut to the CC module, wired in series so pressing either pedal will cut the CC. The vacuum pipes are to release the vacuum in the CC throttle actuator, when you press either pedal the valves open, so releasing the vacuum, they work as a backup to the electrical swiches (so if you have an electrical fault the CC still cannot operate, as no vacuum can build in the actuator with the valves open)

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