'99 Disco I Cruise Control Probs

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alex3324

Well-known member
Oct 19, 2004
510
0
Valhalla I am coming home!
When I bought my Disco last week, the PO told me there was a problem with the Cruise. The switch would illuminate after being pressed, but after pulling on the "Set" button, the cruise wouldn't hold.

I searched the board here and checked my vacuum hoses and the brake-pedal vent valve. All seemed to be in good repair, in fact I vacuum tested both the throttle servo and the vent valve with no problems. Then I tried to pull a vacuum on the vacuum pump but it wouldn't hold. After experimenting with the pump, I found it would hold a vacuum if I plugged the little nipple shwon in the crude MS-Paint drawing below.

My problem: The cruise will now take hold, but it jst keeps accelerating, pressing on the brake stops everything, as does presing the res/- button.

Any thoughts?

discoCCvacuumpump.GIF
 
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dhuddleson

Well-known member
Apr 21, 2004
128
0
Ottawa, Ontario, Canada
Hello,

I am curious to know if your cruise does not work consistently. Or does it sometimes work?

I have a 98 D1 and the Cruise will work "sometimes"... I may start a journey with the dash switch "ON" for cruise, however pulling on the "SET" button does not work. However, 15-20 minutes into a drive (highway crusing), sometimes pulling on the "SET" will result in working cruise!!! And other days it does not work at all ... :(

My hunch is there is something flaky with the actual vacuum pump (engine compartment), or I now wonder if the steering wheel "SET" switch is intermittant...

I'll be following this thread with the hope that I can finally get my Cruise Control working regularly and consistently again...

David
 
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Gabe

Guest
Had same issue with mine. Turned out to be the Relay switch that powers the ECU. Its located under the glove box. Sart the truck and switch the main switch in and out and you can find the relay by touching them and feel for the click. Once found, Turn off you r truck, unplug the relay and replace or, as I have done, pop off the cover and busnish the contacts and reassemble.

Worth a try.

GG
 
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dhuddleson

Well-known member
Apr 21, 2004
128
0
Ottawa, Ontario, Canada
GG,

I like your suggestion to check/clean/replace the relay. I know what you mean by the clicking sound. And sometimes I cannot hear it when pushing the ON/OFF switch...

I should have considered faulty relays, considering all the ones I have swapped out on my Triumph over the years... those Lucas cylindrical plastic ones in TR7's and TR8's etc...

Now wouldn't that be a nice simple fix (if it works!) :rolleyes:
 
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