911SC Cruise Control/Brake Warning, Repair Recommendations?

[jaustinmd]

I've been trying to revive the cruise control on my '82 911SC. I've been through the Bentley diagnostics, the clutch switch has been cleaned, adjusted, and activates the relay, and the last thing I did was test the servo with 6v across sockets 3 & 7 and the engine accelerates, so that tests OK! After all the diagnostics, I plugged-in the cruise control module. Took a test drive and the cruise is still inop, but when I attempt to engage it, the brake warning light on the dash comes on! (The same light the parking brake triggers). My brakes are fine, fluids good, incandescent filament brake lights, and no problems prior to plugging in the module! I reset the light by disconnecting/reconnecting the battery with the ignition "on." When I removed the module and reset the light, it stayed off.

I know that the cruise control module (928.617.127.00) is the usual source of most inop cruise problems and likely is the source of this problem, but I've never heard of the module triggering the brake warning light. My module is used but not "known good." It has a warranty so I suspect I'll be getting another module to try. .

Just thought I'd run this by the forum while I wait on another module in case there is something else I should check! Alternatively, I may just send the used module out for repair so I'll know I'm working with a "known good" module.

For repairs, I've seen Kris Rose (cruisecontrolrepair.com) highly recommended and relatively inexpensive. His website seems only partially enabled and although he mentions to email him, nothing is listed under "contact." I found elsewhere his email is "JamesDean59@gmail.com." Just emailed yesterday and haven't heard back ... is he still in business?

I've also seen ASI (autoecu.com), George Murphy at Performance Analysis Co (perfanalysis.com), "mandigital" on Ebay, and Beckman's recommended. Any recommendations or any that should be avoided?

Thanks,
John

[wwest]

when brake lights are on, come on, the CC is disabled. Something is applying voltage to the brake circuit when you try to engage CC.

[universeman]

Same exact problem here. Subscribed. I had James Dean fix my module and for a while, my CC worked great. Now it just functions as a "Brake Warning Light Activator"


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[jaustinmd]

Originally Posted by universeman

Same exact problem here. Subscribed. I had James Dean fix my module and for a while, my CC worked great. Now it just functions as a "Brake Warning Light Activator"


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So it sounds like an internal failure in the cruise module itself is activating the brake light warning since it doesn't do it with the module removed!

[Kidasters]

I used the guy on e-bay that rebuilds them. Fast turn around and haven't had an issue since he fixed it.

911 928 Porsche Cruise Control Computer Repair Service to Your Unit 92861712700 | eBay

[universeman]

I think it does it with the module removed also. As luck would have it, the module is out right now, so I will test this tonight and report back.

[Uwon]

Subscribed.
Johan

[jaustinmd]

Follow-up:

Well, embarrassed myself again! I just "thought" I had incandescent brake lights but I had LED's! I switched back to incandescent and the brake warning light problem went away! Other than triggering the warning light with LED's in the brake light, the module still doesn't work, though!

I got out the voltmeter and turns out there is a very low voltage all the time on pin 6. It was about 0.6v with the LED brake lights. When I switched to incandescent, it dropped to 0.1v ... apparently low enough to make the cruise module happy! I'm guessing that I could go back to the LED's if I put a resistor in the circuit, but I'm going to leave it as-is 'till I have a functioning cruise control system!

I got an email response from Kris Rose/"JamesDean59." He is indeed in business and now the repair charge is $70 and $8 return shipping.

John

[universeman]

Update on my situation: with module out, hit cruise control stalk - no warning light. So it's not the module. I have LEDs also. Will test with incandescent. I have spoke's LEDs (which are awesome) but I do want my CC to work. Looking forward to chasing this down!

+1 for James Dean / Kris Rose

[rubenmad]

John, were you able to fix your cruise control issue? If so, what were your findings?

Thanks!

[jaustinmd]

I finally went to a Rostra cruise control. The details are here: http://forums.pelicanparts.com/porsche-911-technical-forum/921000-rostra-cruise-control.html

It really works well - better than some modern OEM cruise controls I have used!

John