Cruise control that just continue to accelerate? :)

[jepper]

Hello!

I have a SAAB 900i 16v from 1989.

Have problems with my cruise control, it just continue to accelerate when I push the "set"-button. It finally stops (thank god) when i brake or set the crusie control to "off"
Anyone have had this fault?

Thanks. /jepper
Sweden

[MSOEMiller]

I know exactly what it is. Well, maybe . . .

My mechanic diagnosed this in my '88 SPG during his inspection of the car. I haven't used the cruise control since buying the car, but he tested it.

Apparently, my cruise/turn signal stock is a replacement and a newer style and does not work with the old cruise control relay. The mechanic said he would have to do some rewiring at the relay.

I'm just going to go to the junkyard and get an old stock.

I don't know the wiring requirement, sorry.

[cdaly]

I don't know the details but it sounds like the vac control valve {is there one of them?} is stuffed. Since the brake stops it, the controller is probably fine. The brake operates a separate vac valve which drops it out at this point. Switching off turns off the vac pump.

OTOH, it could be that it's not getting a proper speed signal but I'd think that would prevent it engaging at all...

[jepper]

Thanks for your answers!

I've open the vacuum pump, seems clean and fine.
Also opened the electronic control unit. Looks like new. No bad soldering.
The pedal switches seems ok.

I was just out testing again. Same problem but I noticed that it will keep the speed as long as I press and HOLD the set-button. Work just fine then.
If I then releases the set button it starts to accelerate and accelerate and accelerate... :


Any more ideas?
Thanks guys!

[cjaouich]

Was that you

http://story.news.yahoo.com/news?tmp...d_nm/driver_dc

[jepper]

Huh, I thougt I had a SAAB

[lyricon]

The system works by running the pump to increase speed then holding the vaccuum with a selonoid valve to maintain the speed. It will do a combination of all this to maintain a set speed. Check the electrical connection to the pump. see that it is clean. It gets the speed sensing from the same signla the speedo uses. If that is funky or the connection there is funky it might not be senseing the speed being reached. The turn sig switch sounds like th most likly suspect though. Swaping out another would solve that question. I went through all this with mine and found the control unit dead.
Good luck
Greg

[Groove]

Originally Posted by jepper

I was just out testing again. Same problem but I noticed that it will keep the speed as long as I press and HOLD the set-button. Work just fine then.
If I then releases the set button it starts to accelerate and accelerate and accelerate... :

I have exactly the opposite behaviour. Mine works fine if I just press the button once, but if I hold the set button down, it will continue to accelerate. Wish I could offer more advice, but I'm sure it will be something simple.

[jepper]

Originally Posted by lyricon

The system works by running the pump to increase speed then holding the vaccuum with a selonoid valve to maintain the speed. It will do a combination of all this to maintain a set speed. Check the electrical connection to the pump. see that it is clean. It gets the speed sensing from the same signla the speedo uses. If that is funky or the connection there is funky it might not be senseing the speed being reached. The turn sig switch sounds like th most likly suspect though. Swaping out another would solve that question. I went through all this with mine and found the control unit dead.
Good luck
Greg

The electrical connection to the vacuum pump looks like new.
There is also a relay in the vacuum-pump that works like a valve. looks ok.
I´m going to search for a replacement turn sig. switch just to see if it makes any changes.

[cdaly]

Originally Posted by Groove

if I hold the set button down, it will continue to accelerate.

I think that's correct behaviour. Haven't got the driver's book to hand just now but I seem to remember reading that. Not having CC I can't go and check...

[jepper]

Solved!

I bought a new signal switch today and that stick had the option "TIP" on the cruise control buttons wich it hasn't on the one in the car. It seems like someone before me hav changes the signal switch to an older version or something like that Iäm so glad I didn't burn something Now it works just fine *aaah*

Thanks so very much everyone, especially to MSOEMiller who had the right answer for my problem