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Join Date: Nov 2005
Location: Jersey Shore
Posts: 615
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Cruise control only works on special occasion - 81SC
Need some thoughts on this one....
81 SC - Cruise control will not operate/respond approx 99% of the time. Hit the stalk/control lever and nothing. I try it often just for the fun of it because every now and then (like once or twice a year), it perks up and works and seems to work consistently during that 'outing'. Shut the car off or try later in that same day and forget it - no response. May not see it work again for months/year. When it works, it seems to work fine - holds speed, doesn't surge, brake turns it off, accel lever works, can set it, reset it ; column switch works fine, no problems. Anyone got any ideas? I would want to say one of the components is shot b/c it usually doesnt respond but when it decides to work, it seems to work as designed - actually holds highway speed fairly smoothly. Tried shotgun approach of replacing clutch microswitch which did nothing. Ideas? |
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07-18-2006, 12:24 PM
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It sounds like a bad electrical connection or the "brain" needs to be replaced. If you take the 911 on long trips like I do, it would be worth taking it apart and check continuity. Also check the vacuum connections in the engine compartment. Start with the most obvious things first, then get out the multimeter and wire diagram to chase it down.
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07-18-2006, 12:36 PM
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Location: SOCAL
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My 1983 SC used to do the same thing, and now it deson't work at all (though I admittedly don't try it anymore -- maybe it would work once a year like yours). All of the past posts I read on this topic indicate that this is very common, and is due to the "brain" going bad. I think the brain is under the pass seat, and is common with a Mercedez Benz unit, so not hard to find, but kind of pricey $200 or more??).
Good luck - keep us posted. --DDD
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1983 Ruby Red Metallic 911SC 2005.5 Audi A4 2.0T Quattro 1991 Mazda Miata Special Edition British Racing Green www.DDDinMN.wordpress.com |
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07-18-2006, 02:33 PM
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rusnak and triple D- thanks for the thoughts.
looks like multimeter test procedure is in order with the thought that the brain may have to go. thanks |
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07-18-2006, 02:54 PM
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Just drive the PORSCHE on those special occasions.
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07-18-2006, 03:45 PM
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Location: Cleveland, Ohio
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check the vacuum line that goes into the cruise control module(? it looks like a large fuel filter) in the back of the engine compartment on the driver's side. After my "best in town" mechanic replaced my clutch, he said my cruise ran intermittently. Vance (vesnyder) found my vacuum line to be half on when he helped me replace my rear shocks last spring. My cruise has been working ever since.
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Pete Brown '87 911 Coupe '20 718 GT4 '25 Aviator '25 Mach E |
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07-18-2006, 06:04 PM
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Would that vacuum line explain my problem? Mine works intermittently as descirbed in first post, only mine is not nearly as long between - maybe once every 3-4 attempts. But, when it does work, it seems to very methodically speed up and down about 5 mph. Not quickly, but steadily.
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Shane - 1984 928S |
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12-05-2006, 09:35 PM
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v8
A replacement brain fixed my problem and speed holds constant nicely. I heard of vaccuum lines causing 'bleed off' in speed but not surging you describe. Actually i have heard that a misadjusted cable/linkage could cause surging. I am guessing your brain is on the way out...see if you can swap someone's in and see if it helps (takes 10 mins to swap brains). |
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12-10-2006, 05:22 PM
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thanks
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12-12-2006, 04:51 PM
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