cruise control

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rash_1
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Sun Oct 03, 2010 10:29 pm

hi still having trouble with my cruise control the clutch swith and brake switch is all in place, anyone know what else it could be. many thanks
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Brianmoooore
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Sun Oct 03, 2010 10:46 pm

rash_1 wrote:, anyone know what else it could be. many thanks
Not unless you expand a bit on "having trouble".
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rash_1
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Sun Oct 03, 2010 10:55 pm

sorry about that, it not working at all.
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Brianmoooore
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Sun Oct 03, 2010 11:07 pm

Disconnect the cruise ECU and the actuator. Use a meter to check that there is a low resistance (not zero) between the green/red wire (9) of the ECU plug and earth.
Switch the meter to volts, and check that this wire goes to 12 volts + when you press the brake pedal with the ignition on.
Connect a 12 volt 5W or 10W bulb between the purple/white (1) of the ECU plug and brown (23) and check that it lights with the ignition on.
Grrrmachine
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Wed Dec 15, 2010 9:21 pm

Sorry to resurrect this thread; my cruise hasn't worked since I got it. I've tried the above things and got successful results, and I've also bench-tested the actuator (fine) and the column controls (fine). So I'm out of options, other than swapping the ECU for another one.
Grrrmachine
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Sun Aug 07, 2011 3:42 pm

Another six-month resurrection. I've put in a new ECU, I've re-done the tests (1.5 ohms on pin 9, switching to 12V with ignition on; pins 1 and 23 light up a bulb), and I've installed a clutch switch, but I'm still not getting my cruise control working.

I tested the controls on the bench with a multimeter, and they worked, but is there a chance that the bolt that holds them (and the windscreen wiper lever) is a circuit component (like an earth point) because I've used the original windscreen wiper bolt and not the longer cruise control bolt? That's how desperate I am in finding points where this might be failing.
grantorino
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Wed Aug 10, 2011 6:29 pm

I presume you've removed the gauge cluster and confirmed the cruise control speed sensor wire is plugged in firmly into the green connector on the back of the speedometer? There are at least 2 pins within this green connector. It doesn't matter which one you plug into.
1986 325 ES stick shift 137,000 miles, 1973 Mercedes 280C
Grrrmachine
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Wed Aug 10, 2011 6:36 pm

Yeah, I've disconnected and reconnected that wire quite a few times. Is there any way I can check it, such as at the ECU plug?

My next step will be to open up the actuator to make sure things haven't rusted solid inside there, and to free up the bowden cable.
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