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Boost Issues, Cruise Control, Switch Adjustment Posted by Bill Homer [Email]  (#3427) [Profile/Gallery]
(more from Bill Homer) on Tue, 8 Mar 2005 11:33:19
In Reply to: I believe that it is the other way around, Ari [Profile/Gallery]
, Tue, 8 Mar 2005 10:43:02
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The wiring for these switches may have changed over the years, what I stated in my post I recall is valid for 1994 cars - when I was having boost problems, I looked at these switches as a possible cause. Of course there were many other issues, and I eventually traced my boost issues to a combination of defective BPC (one side's coil was fried), defective ECU (drive transistor for the BPC coil was probably taken out by the fried BPC), and a defective cruise control module (signalling "ON" all the time, even though it controlled speed perfectly). This was a tough problem to solve!
I guess that brings up another cause of base boost, which hasn't been previously suggested: the Cruise Control (CC) module. Mine was signalling "ON" at all times, which tells the ECU to limit the car to base boost, a safety measure. Note that the "Cruise Control" dashboard light was not illuminated at all times, only when the cruise was actually switched on, but the signal provided by the module to the ECU was always high, approximately 10V even with the ignition off. On a 1993-94 cars, there is a relay in the CC module which provides this signal, I assume it's default (deenergized?) output value is "high" or "ON".
The way I found this was to go for a drive with a Tech-II plugged in, when my mechanic said "turn off the cruise", which was being shown on the Tech-II display, even though it was off. On 1994 cars, unplugging the cruise control module (located under the dash above your left knee) will allow this wire to return to a "low" signal (ground voltage or close), no more boost limitation. I do not have the diagram handy and Townsend's site, which has a digram of the cruise system, is currently down. Note that different years had very different implementations of cruise control, driven by a vaccum motor on pre-1995 cars and a stepper motor in 1995+ cars. What year is your car again?
The clutch and brake pedal switches are adjustable, at least on some cars. I have seen the procedure elsewhere, but the genuinesaab.com (a sponsor) site has a writeup in the Tranmission/9000 Clutch Pedal Return buletin: "Readjust the cruise control pedal switches and brake light switch by depressing each pedal and pulling out the racheting (sic) plunger on each successive switch. When the pedal is released, the switch will then self adjust." I've never had to try it, so I can't comment.
posted by 136.182.2...
, Tue, 8 Mar 2005 07:42:03, Tue, 8 Mar 2005 10:09:27, Tue, 8 Mar 2005 10:43:02, Tue, 8 Mar 2005 11:33:19 <-- Viewing This Message, Tue, 8 Mar 2005 11:41:43, Tue, 8 Mar 2005 15:33:12
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