[bill3]

Coming back from Watkins Glen, Cruise control is working nicely on I-81. It starts to get dark so I turn on the lights and "poof", cruise goes off with what briefly smelled like an electrical short. Cruise wouldn't respond to any inputs after that. I just checked the fuse and it seems fine (and it controls other items which are working) so, unfortunately, it doesn't appear to be the fuse.



Suggestions and ideas from the brain trust?



Car is stock electrically and mechanically (except suspension).



At the track, the right rear brake light stopped working so I replaced it with a single filament vs. the dual filament that was installed (that was the only bulb in my set of spares and it seems to work for both brakes and lights). Could that be a factor??



Thanks for any and all suggestions and ideas! In a month or so, we will be driving to VIR (500 miles each way) and the cruise helps my back a lot



Bill

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[JTP]

I had a similar situation, cruise control quit along with the sunroof. All fuses look fine.

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[Darryl]

Yes, if third brake light is inop, cruise will not work. Had that experience on my Coupe when I first bought it. The third brake light was non-existent and the connections were all corroded and nasty. When I put a working assembly on with all working bulbs, the cruise mysteriously started to work fine. Hopefully, that's your problem since it's an easy fix rather than getting into diagnosing the cruise control circuits and computer module.



- Darryl

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[DAK]

Check the wire on left side of driver footwell leading to the clutch pedal switch, it broke on mine and caused cc to be inop.

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[JTP]

All of my brake lights work, I'll check that wire to the clutch next.

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[JWahlsten]

The cruise control brains are known to fail in the 944 series via cold solder joints on the boards. If you have some talent with a soldering iron you can bring it back to life. If not, a friend of mine Joe Jackson used to repair them. I'm not sure if he's still doing it, but you could hit him up at joejackson951 at comcast.net.



Of course try the easy fixes first...

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[bill3]

Yesterday I replaced the right rear brake/running light bulb (which blew at Watkins Glen and I put in a single filament bulb) with the proper dual filament bulb. Went out for a drive and the cruise control works like a champ! Thanks for all the advice: I was sure it was something else as the cruise control on my 944S2 was very finicky and often decided not to work.



Who would think that the tail light circuits would affect the cruise control?!? Must be buried in the wiring diagrams some place.



So in this case, the easy fix worked.

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[ds968]

[quote name='bill3' timestamp='1411939061' post='162590']

Who would think that the tail light circuits would affect the cruise control?!? Must be buried in the wiring diagrams some place..[/quote]



Bizarre. Then of course, it's Porsche - nothing needs to make sense. Maybe they thought if you disengage the cruise control by using the break and the tail lights don't activate when you do that it's a safety issue ( for the car behind you ? ) so they linked the two in such a way that one affects the other, both ways. ??

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[williamoss]

my sunroof works fine, but my CC does not engage, what else is on the same circuit? Is the fuse under the hood or in another location? And does it look like a fuse or a small black box as in a control module?

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[Waylander]

the rear brake lights are also linked into the ABS system

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[ryker]

In the several 968's that I have owned, two of them had inop cruise. In both cases it was the cruise control module that is located in the driver footwell. A bit difficult to get to the 2 nuts that hold them on. I know of a guy in Delaware who fixes of the modules for the Vanagons that I restore. I sent him one of my Porsche modules and he repaired it for $45. That module is in my current car and works great. I would encourage anybody with inop cruise to send Joe an email, joejackson951@comcast.net. As stated above, the solder joints fail over time.

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[williamoss]

My cruise control is still not working. I just check all 3 brake lights and all 3 are OK. I also tried to find a fuse that might be blown in the main  fuse box under the hood. But in the main fuse box there is no fuse labeled as speed control, cruise control etc. Other have said they checked the fuse. Where is this mystery fuse located and do you know the number of the fuse, i.e. the location not the size. Mine is a 1995 coupe. Also does anyone have a factory manual and know on which page in the schematics is the cruise control shown? My sunroof also works.

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[kwikt]

Check both clutch and brake peddle position sensors and make sure they are adjusted properly. Will your car turn over with it in gear and not pressing the clutch??

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[williamoss]

Check both clutch and brake peddle position sensors and make sure they are adjusted properly. Will your car turn over with it in gear and not pressing the clutch??

 

No the car will not turn over with it in gear and no clutch ? 

 

So now what any ideas?

 

And again I ask where exactly is the fuse for the Cruise Control  as it is not listed in the main fuse box, yes some have said they checked a fuse?

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[az968]

So on my way to Tahoe, my cruise control dropped out, stopped working. Fuse is good, will check brake lights tonight. And then clutch pedal wiring as described above.


I guess the lack of cruise control is why I couldn't keep my speed down during the mountain drives.


Williammoss, did you ever get your CC working?

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[Ernie]

I did a 3rd brake light led strip and lost my cruise control. As previously mentioned... check your brake lighting.

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[az968]

All three brakes lights work. So on to inspecting the wiring to the clutch. As I recall, I wasn't changing gears when it failed. Had just braked to slow down, then accelerated using the cruise control "resume" feature and then moments later it went "thunk" and fell out of CC. I'm guessing the control unit, but easy checks first.

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[az968]

Not having driven another 968 while using CC, is it normal to hear a "thunk" sound when depressing the brake pedal and deactivating CC? I had been hearing that for a while before it failed last week. If that's not normal, the problem may be with something other than the control unit.

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[lbpesq]

Bob, mine doesn't "thunk". My cc died a few years ago. I tried re-soldering, but it didn't work. I found a used unit and it's been working fine ever since. As I recall, one of the two screws that hold it in is almost impossible to remount due to extremely poor access.


Bill

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[az968]

After further diagnosis I have found the fault with the cruise control.  I checked all the simple electrical things (rear brake lights, the little switch on the clutch and brake petals) and all looked good.  Confused by the "thunk" feeling that everyone told me they didn't hear/feel I started looking again through PET for something mechanical and realized ("duh") that there's a cable running from the drive link in the engine compartment to the accelerator cable that maintains the speed. Popped the rear engine cover and sure enough the cable had popped off the lever on the drive link. Ball and socket.  Inside the socket is a plastic bushing.  Broken apart.  New cable on order from Germany for $70. I decided to replace the whole cable rather than just wire the socket back to the ball lever cause if it failed at one end of the cable, its gonna fail at the other.

 

Hopefully after I get the part I can be cruizin' again.

 

You'll might look at your cables in case someone else s is fixin' to fail.

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