salukijac

Who has fixed their own module? Or where have you sent your module for refurbishment?

I did a quick search today and found a few threads but no good info on dyi repairs.

Here's the symptom...the cruise control will sometimes engage and will accelerate and then disengage. As I was talking to my mechanic today he said that's usually a bad module.

I opened mine today and took a peek and didn't see too much out of the ordinary except for one component showing a little brown spot. Without any schematics it's hard to even Id the component. So what say you?

rusnak

The 911SC and later editions of the Carrera manual of Bentley Pubs has a procedure to test the cc switch. I'll see what I can find in it. I've been pushing the envelope so to speak on scanning pages outright.

dshepp806

Have you a pic of the "spot"? Or the board, for that matter?

I used to have the damned schematic for MY89 but lost it on a drive failure with no backup for that file. Or, at least, I can't find it.....I'm gonna fire up one my old servers and look there...see what shows.


Best,

Doyle

rusnak

I'm bumping this thread too. I can't find my 911SC service manual. It describes how to check the CC switch with a multimeter, that way you can be reasonably certain it's the brain.

salukijac

I can do the check in the Bentley, probably will not get to it until later this week.

I'll also take the module out and take a picture when I get a chance.

salukijac

Here are some pictures of the module. The component that has a brown spot seems to be a resistor. 2RO 5%. I'm a little rusty with my electronic components but if it is a resistor I should be able to unsolder it and check it with an ohnmeter.

Attachment 454011

Attachment 454012

Attachment 454013

Attachment 454014

Lorenfb

Looks can be deceiving!

dshepp806

Yes they can,..especially that wattage resistor. I'd still disconnect one end and measure, as it's clearly been quite hot.

I'd like to see shots on the bottom side (looking closely at solder points..)

Could be anything from a dollar diode,..to a 79 cents cap to the NLA chip..........

Good Luck

(bet ya' Loren's fixed a "few" of these!)

Doyle

Doyle

Edgy01

My God electronics has come a long way since then!!

Suspect also a simple solder failure to be the cause. Automotive components have issues with shock.

dshepp806

For sure,..and a reason to see pics of the bottom of the PC board.

,..look closely, under magnification.

Best,

Doyle

dshepp806

Guarantee you those vertically mounted electrolytic capacitors (if original) don't improve over time....usually tied to the power supply buss, at that.

Hope you can trace back from the heated power resistor to where it's connected (i.,e., "which active component pulls current through it"). Maybe Loren will speak (specifically) about the diodes on this PC board (black ones).

I still can't find my damned print on this and am not versed on the circuit from experience....many of the components can be tested, passively, I'm sure. The ICs would be another matter..

Come on,..more bottom-side pics!!!!!!!!!!!!!!!

Best,

Doyle

dshepp806

I checked my Bentley (89) and it does contain a cruise control T/S Table (C)...however I'm not sure if mine is like yours,..pin for pin on the connector. Maybe somebody will chime (Loren knows....)...several resistance checks on the various pin combinations.

Best,

Doyle

theiceman

Yeah Doyle that is exatly waht i thought when I saw the electrolytes. I don't hacve cruise on my car but doesn't it use other inputs too ? such as a switch on the brakes to disengace it etc ? what about those as possible suspects ?

dshepp806

Yes,..the table clearly looks at some of these inputs that you mention. Maybe someone can look into the Bentley for the gent's car (MY) and see what table they see....I'll be glad to post what I have for my '89 but don't want to lead the gent astray. Surely this table exists within his model Bentley manual?

Someone check, please?

salukijac: have you a Bentley manual?

Thanks,

Doyle

rusnak

scarceller was putting together some stuff on the CC module IIRC. Sorry I can't find my 911SC manual yet. My Carrera manual is the first edition, which was written before the SC manual, and it does not have the CC info.