Cruse Control Question

[AV325i]

The cruse control on my 80 325iX will let go after about 30 seconds to a minute. Any ideas?

I have a 90 325i parts car, so I could swap out parts, but I don't know where to start. There is that servo-motor-cable thing (sorry-I don't know what it is really called) which seems easy to swap. Is that a reasonable place to start?

I got it all disconnected except for this line running into the firewall (holding in my hand in the picture) I assume it goes to the steering column. how do I disconnect this? Or am on on the wrong track starting here?

Thanks!

Not sure why my picture is not showing up, but you can use the link

http://www.r3vlimited.com/gallery/showimage.php?i=21333&c=3

[jlevie]

The first things I'd consider as a cause would be the inputs/controls. Pin 8 of the cruise control module must see ground through the brake lights circuit, which passes through the clutch switch on a manual car, for the module to be engaged. And pin 3 (only used on an auto) must have no voltage. A problem with the cruise control stalk or it's wiring could also be a problem. The speed signal must also be good.

If I could not find a problem there I'd swap out the module before I'd change the actuator.

[AV325i]

Where is the cruise control module? Under the dash or in the engine compartment?

My iX is an auto, so what should I expect on Pin 3?

When you say "pin 8 sees ground with break" do you mean it should read 12 V and then go to 0 V when I touch the break? Does it go back up to 12 V when I release the break? Sorry, I'm new at this.

Thanks

[jlevie]

The module is behind the dash.

Pin 8 needs to see ground through the brake light circuit for cruise to be engaged. When you hit the brakes pin 8 sees 12v and cruise disengages.

[Bmjpv]

brake switch

My $$ is on the brake pedal switch dropping the cruise out, basics,check this first. Good luck , Joe

[AV325i]

Thanks. This is helpful I will try to find the module and pin 8.

If I understand correctly, then it should read 0 V until the break pedal switch is released, then it should go to 12 volts which shuts the cruse off.

So what does failure look like. Will I see 2 Volts rather than 0 V, or will the circuit spike a random 12 V (in which case I may not see it ) and I am better off just replacing the break pedal switch.