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Discussion Starter · #1 ·
Hi everyone,
Car: 9000CS Carlsson 2.3t
I have been experiencing APC gremlins for several months now and have read through most of the bulletin board and tried various methods and parts. I bought a new APC solenoid on the basis of much of the info I found but this didn't cure the problem. Expensive fault finding!
The car is not achieving full boost, only ever base boost no matter what conditions. Suspect APC valve was the culprit.
Seward Saab in Christchurch have been good for advice and even lent me a DI cartridge to test out. No luck. I followed the Townsend Imports fault finding guide through to the brake sensor test and found something.
If you press the brakes lightly under full throttle you get full boost. However this is a little erratic and yesterday ended in the overboost protection working.
I have a Red Box APC in the Carly and am wondering if anyone knows of this problem (Sewards didn't) and can it be fixed without replacing the APC box!
I have not yet tested to see the signals on pin 32 of the APC box (Brake Sensor input) but as the Cruise Control and Brake lights work perfectly I cannot understand the problem.
Any clues anyone?

Thanks for your input (in advance)

Duncan
 

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All I can think of is to check the brake sensor input, as if the APC thinks the car is braking it will dump the boost. Sorry I can't be of any more help, I have a similar problem in my 900T16 and if I find anything I'll post the info.

Neil
 

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Discussion Starter · #5 ·
Something must be connected to the wrong place but from the Saab wiring diagrams this brake pedal sensor switch feeds the Cruise Control as well which works perfectly. One question if anyone can answer. On a CS do the brake lights normally operate with the ignition off. I am wondering if I should be chasing a bad earth or something?
I must get out over the weekend and see what is the feed to the APC from the brakes.
 

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Duncan,
Yes, the CS brakes normally operate with the ignition off and yes it sounds like it may indeed be a bad earth.
Seems that something is causing the brake sensor input to be high when it should be low. You could try disconnecting that input to the ECU, also measure the voltage on it with a DVM it should be zero except when the brake is applied.
 

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Discussion Starter · #7 ·
I was thinking pretty much the same thing as you Derek and that was going to be my first port of call. However if it is working properly I can't really think of where to go next. All hypothetical as yet I feel, but having looked at the connectors into the APC box I am going to struggle to find the correct wire from the brakes!
 

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Townsend has the pin number of the connector - simply pull from APC line it up in the right direction to the Townsend schematic and stick your prob in (very easy) to check - thats what I did. Just dont leave ignition switched on for long periods.
 

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Pressing the brake peddle activates the break servo which works off inlet manifold pressure (except auto box engines, which have a seperate pump).

Maybe the effect of pressing the break peddle (i.e. causing boost to increase) relates to inlet manifold pressure variation rather than ECU signals??

Just a thought, for what it's worth!
 

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Discussion Starter · #11 ·
To follow up I have had a nice little chat with the very helpful people at Abbott Racing and they feel it is caused by a TCS/APC problem, something we were experiencing difficulties with last year but were told was fixed.
Anyway I have invested the grand sum of £40 +VAT in one of their manual boost valves and will report progress thereof when it arrives in the post tomorrow.
I know it is a bit of throwing in the towel but I just want to be able to chase those Golf GiTs again and win.

Thanks for everyones input. If I ever fix the fault I will send /john a PDF file with instructions to post somewhere.

Cheers,

Duncan
 
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