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  #1  
Old 30th January 2011
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Default Cruise Control 92 900 vert

Cruise light will come on but it will not engage. I've check everything but the relay, or is there a relay? All vacuum hoses are attached and appear not to be dry rotted.

Is there any thing else to check? Could the unit by the driver side quarter panel be bad and I just can tell it by looking at it?


Any suggestions?


Thanks===rn
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Old 30th January 2011
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Default

Good diagnostic page: http://townsendimports.com/Web/elect...isecontrol.htm


My experience is that the cruise vacuum controlled switches can leak with time. I had temporary luck "fixing" them with some plummers silicone to make a better seal, but ended up replacing.

Also, there is a switch that limits boost when the cruise is activated that is also prone to leak. I bypassed mine completely.

Be prepared to pull the knee pad and have some spare vacuum hose on hand for tests or replacement.

Good luck!
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  #3  
Old 30th January 2011
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or has the actual switch on stalk failed
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  #4  
Old 30th January 2011
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Wow, that looks like a weekend job. Thanks for the replay and the article. What switch on the stalk are you referring to 16?
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  #5  
Old 30th January 2011
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the cruise control switch is part of the indicator stalk on UK I think or the other side(never had cruise on my 900's, but know someone who has)
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  #6  
Old 30th January 2011
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My experience is that the cruise vacuum controlled switches can leak with time. I had temporary luck "fixing" them with some plummers silicone to make a better seal, but ended up replacing.


Are you talking about the one behind the drivers headlight behind the panel?
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  #7  
Old 30th January 2011
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Quote:
Are you talking about the one behind the drivers headlight behind the panel?
I'm talking about the vacuum switch behind the brake/clutch pedals.
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  #8  
Old 31st January 2011
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I've had 3 'verts ('92 & 2x94), all of them with the same problem: The cruise control would sometimes work ... and then sometimes not. It seems to be completely random. The only trend that I'm suspecting might be there, is that it helps to have the heat on high ... but it might be imagination. If it's a trend, it's weak.

I've run through the entire troubleshooting chart from the Bentley Bible (excellent chart by the way). Every single component seems to work flawlessly. No leakage from any of the vacuum switches. I've taken the stalk switch apart and put it back together. Still no improvement.

I'm mystified, and interested in all responses to this posting.
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  #9  
Old 31st January 2011
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Quote:
Originally Posted by JKlaveness View Post
I've had 3 'verts ('92 & 2x94), all of them with the same problem: The cruise control would sometimes work ... and then sometimes not. It seems to be completely random. The only trend that I'm suspecting might be there, is that it helps to have the heat on high ... but it might be imagination. If it's a trend, it's weak.

I've run through the entire troubleshooting chart from the Bentley Bible (excellent chart by the way). Every single component seems to work flawlessly. No leakage from any of the vacuum switches. I've taken the stalk switch apart and put it back together. Still no improvement.

I'm mystified, and interested in all responses to this posting.
Same problem here. When it was new and under warranty we took it to the dealer at least a hand full of times to correct the problem. They always said it was fixed or "we couldn't duplicate the problem." Once, I was driving and the cruise was working fine, and all of a sudden, it just stopped working and wouldn't re-engage. It's still intermittent.

Dustin
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  #10  
Old 31st January 2011
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just keep the foot at the same angle works just as well
unfotunately or fortunately we don't have 'LONG' roads where we can use this feature for long anyway in uk, as there is always someone jamming on there brakes in front on the M-ways
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  #11  
Old 6th February 2011
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Quote:
Originally Posted by 16saabs View Post
just keep the foot at the same angle works just as well
unfotunately or fortunately we don't have 'LONG' roads where we can use this feature for long anyway in uk, as there is always someone jamming on there brakes in front on the M-ways
Well then, can we swap parts?
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  #12  
Old 6th February 2011
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I have a 'scrap' C900 turbo vert and that's fiited with cruise, the car will be stripped out in the warmer weather, for parts for our own(hence purchase), but non of us have cruise(5 x900's) if you have'nt been successfull in finding parts(sorting prob) give us a PM
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  #13  
Old 6th February 2011
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Default Cruise Control Common Faults

These are the common weak points:

1988 or older- Bad vacuum lines
1989 - Bad Speed Sensor
1990 or later - Misadjusted or faulty Pedal Switches

Of course, your car may have its own individual problem.

You can manually power the Vacuum Pump and watch the Throttle open to check the mechanical portion of the system.
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  #14  
Old 6th February 2011
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Thanks, Jim. I'll give the pedal switches a good looking over when I take the Norwegian 'vert out of winter storage. That'll be in April, I hope.

:-J
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  #15  
Old 6th February 2011
James Bond James Bond is offline
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Quote:
Originally Posted by JKlaveness View Post
I've had 3 'verts ('92 & 2x94), all of them with the same problem: The cruise control would sometimes work ... and then sometimes not. It seems to be completely random. The only trend that I'm suspecting might be there, is that it helps to have the heat on high ... but it might be imagination. If it's a trend, it's weak.

I've run through the entire troubleshooting chart from the Bentley Bible (excellent chart by the way). Every single component seems to work flawlessly. No leakage from any of the vacuum switches. I've taken the stalk switch apart and put it back together. Still no improvement.

I'm mystified, and interested in all responses to this posting.
Did you check the signal from the speed transducer and also how do you check if the ecu is good? (I have the same prob!).
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  #16  
Old 10th May 2011
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I took the 'vert out of winter storage a month ago, but only got around to checking the Cruise Control today. Took me 3 hours.

* There are no problems in the cable harness. I tested every single cable, and found excellent connectivity everywhere.

* The whole vacuum system works flawlessly. I can run it manually by feeding 12V into the cable harness from the CC Electronic Control Unit under the dashboard (+ to pin 1, - to pin 6 & on/off to pin 7).

* The pedal switches are reliable and do exactly what they're supposed to do.

* All voltages and signals get through to and from the cable harness for the electronic control unit, as described in the wiring diagram.

There are two things left that I don't know how to check.

1) The speed transmitter behind the instrument panel gives out a steady 12,7V (full battery voltage) on pin 2 when the car is stationary. The moment it starts to roll, the voltage drops to 6,69V. The voltage seemed to rise a little when I drove fast, but the difference was small (7,2V at 100 km/h), and there was some fluctuation.

2) The electronic control unit under the dashboard might be faulty.

I have both a spare speedometer (with a speed transmitter) and a spare electronic control unit, but both came from a car with exactly the same problem as my present 'vert, so I don't think I'll learn anything from starting to switch parts around.

Should I just give it up, and accept that I only have a Cruise Control now and then?

I drove the car for 6 hours yesterday, all the time with the heat on high. The CC started to work after about 1 hour, and kept working until I had to take a 1 hour break because of a ferry ride. When I drove off the ferry, the car was cold, and I didn't get the CC to work again ... but I had a LOVELY ride home nevertheless. It was as dark as it gets in Norway on a summer night, and I can attest that dew does amazing things to how a landscape smells.

:-J
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  #17  
Old 11th May 2011
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My experience and lots of reading tells me that on '92 and newer, the electronic unit (brain) is the most common problem. The '91 and older did not have this problem, but the brains won't interchange without rewiring. My '93 turbo used to work fine sometimes, quit working when it felt like it, start working again, and so on. I swapped the brain out and it worked fine from then on. Vern
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  #18  
Old 11th May 2011
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Thanks a million. I'll turn my attention away from the speed sensor for the moment, and focus on the ECU. Since I have a spare, I can open it up and look at the circuit board and connections inside. Maybe I'll find something. And if not, spares seem to go for around $50 on ebay.

:-J
Jørgen
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  #19  
Old 11th May 2011
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Great reading - I will follow it with interest. My 92 Cruise Control works fine, but who knows. Mine came from Singapore.
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  #20  
Old 11th May 2011
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My interpretation of the fluctuating voltage from the speed sensor
>> 1) The speed transmitter behind the instrument panel gives out a steady 12,7V (full battery voltage) on pin 2 when the car is stationary. The moment it starts to roll, the voltage drops to 6,69V. The voltage seemed to rise a little when I drove fast, but the difference was small (7,2V at 100 km/h), and there was some fluctuation.<<
is that the sensor is sending out pulses, with a frequency that depends on the speed of the car. If I had access to a 12V occilloscope, I could probably confirm this. An alternative, come to think of it, is to connect the signal to a loudspeaker that I don't particularly care about (or through a resistor). Might be fun to try. The worst that can happen is that the speaker burns up.

:-J
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