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Poor-sche Lover's Avatar
 
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Location: Pittsburg, KS
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Cruise Control Questions

I'm trying to figure out why my cruise control doesn't work. This is not the normal "my cruise won't hold" problem that EVERYBODY seems to have. Mine will not work at all. I have definitely determined that it is not the steering column switch. I have started going through the Bentley troubleshooting, but I can't even get through the first step. It says my ohmmeter should read infinity between Pin 3 and ground. I'm only getting 96-99 kilo-ohms. My latest thought is that I need to pull out the clutch switch, but I'd like to solicit the board as to suggestions for what to do next. Any ideas?

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Alan
Past: '74 914 2.0, '82 911 SC Targa, '88 911 Cabriolet, '88 911 Cabriolet again
Present: '00 Boxster S
"Happiness is not around the next corner......happiness IS the next corner."
Old 04-28-2009, 03:18 PM
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Alan,

While trying to help out on an other cruise control question here:

Had what I thought was an incident

I noticed what might be an error in the Bentley manual - The '88-'89 Carrera models used an electric servo (not vacuum) for the cruise control. After examining the CC diagrams for those and previous years, it appears that the Troubleshooting guide in the Bentley Manual (p. 960-12) may not be correct as far as the terminal numbers are concerned for the '88-'89 models. After comparing the the '88-'89 diagram (p.970-62) with the earlier diagrams I believe the correct location for the ohm meter for the first 2 items of the troubleshooting tests is terminal 14 to ground. Take a look at diagrams and you will see the difference. The errors continue with other tests as the troubleshooting guide is referring to the earlier vacuum operated CC units.

Good Luck,
Andrew
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'88 Carrera Cab 3.2 Diamond Blue Metallic - ERP Polybronze Bushings, ERP Monoballs, SW Chip, Bilstein Sports, 930S Steering Wheel, DAS Rollbar, Sparco 5pt Harness, Hunsaker Sport Seats, Dansk Pre-Muffler, MK 1in-1out Exhaust, Magnecor KV8.5 Wires
'86 944NA, Sunroof Delete, Track Rat, Full Cage
'72 914 1.7 Guards Red / '02 Audi S4 Light Silver Metallic
Old 04-28-2009, 07:05 PM
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I will definitely try that. Thanks. I was wondering because nearly all the tests were failing. I must admit that I'm not great at reading those schematics. Can anybody "translate" the pin numbers on the 84-87 to the pin numbers on the 88-89? Pin 3 is supposed to be #14.
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Alan
Past: '74 914 2.0, '82 911 SC Targa, '88 911 Cabriolet, '88 911 Cabriolet again
Present: '00 Boxster S
"Happiness is not around the next corner......happiness IS the next corner."
Old 04-29-2009, 03:34 AM
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Okay, here's what I think I've figured out so far. The pin numbers on the troubleshooting guide in Bentley's are, indeed, all wrong for the '88 - '89s. The pins involved in the troubleshooting guide are #3, #6, #7, #8, #9, #10, #11, and #12. Here is my "translation guide". I will go from the '84 - '87 pins to the '88 - '89 pins.

#3 -- #14
#6 -- #8
#7 -- ???
#8 -- #3
#9 -- #4
#10 -- #6
#11 -- #11
#12 -- #12

If anybody can correct me or help me out with what #7 is supposed to be, I'd appreciate it. #7 is supposed to go directly to the cruise control drive, but there are 5 pins on the '88 - '89 that it could be. I'll do a little more rooting around tonight to see what I can find.
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Alan
Past: '74 914 2.0, '82 911 SC Targa, '88 911 Cabriolet, '88 911 Cabriolet again
Present: '00 Boxster S
"Happiness is not around the next corner......happiness IS the next corner."
Old 04-29-2009, 04:57 AM
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Alan,

I think you have got it, but be careful with the results as the devices are different, so there is really no way to determine if the tests will cross between the different CC systems. The terminal 7 may not have a corresponding terminal on the later models.

In my experience the most common cause for problems is the clutch switch. Most times it is just a position adjustment that needs to be made, or sometimes the little lever on the switch gets bent. The first two tests with the revised terminal numbers should tell you if it is the clutch switch. Or you might just have to test the switch directly.

Andrew
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'88 Carrera Cab 3.2 Diamond Blue Metallic - ERP Polybronze Bushings, ERP Monoballs, SW Chip, Bilstein Sports, 930S Steering Wheel, DAS Rollbar, Sparco 5pt Harness, Hunsaker Sport Seats, Dansk Pre-Muffler, MK 1in-1out Exhaust, Magnecor KV8.5 Wires
'86 944NA, Sunroof Delete, Track Rat, Full Cage
'72 914 1.7 Guards Red / '02 Audi S4 Light Silver Metallic

Last edited by aj88cab; 04-29-2009 at 05:38 AM..
Old 04-29-2009, 05:15 AM
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So, I guess this one can go under the "admit to your stupidity" thread, but I figured I should give this some closure just in case others are searching. After I figured out the right connections, I spent a LOT of time with the multimeter. I even tested for continuity to the column switch and the servo. I couldn't find ANYTHING that wasn't working as expected. So, I have spent the last several weeks searching the forum for any advice. Somewhere, I saw a reference to a cruise control relay. I had previously assumed that this was the relay that's on the brain itself. Not so (apparently)! So, I go to my fuse box, and there it is. There's NO FREAKIN' RELAY! It's just gone. Geez! A quick trip to salvage a relay off the 914, and all is well. What a way to spend a few weeks of studying! Anyway, thanks all for the guidance.

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Alan
Past: '74 914 2.0, '82 911 SC Targa, '88 911 Cabriolet, '88 911 Cabriolet again
Present: '00 Boxster S
"Happiness is not around the next corner......happiness IS the next corner."
Old 05-30-2009, 04:28 PM
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