kriswinner

Cruise does not work --- inputs do not appear in diagnostics

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I have a 1993 Riviera and the cruise control does not work.  I just purchased the car and it hasn't worked since I got it.

I was going to use the built in diagnostics to check the status of the cruise control inputs, but BI71 through BI77 do not appear on the diagnostic list.

 

Any idea what is happening?  My assumption was that my diagnostics were the same as the Reatta 90-91 list.

 

Any help is appreciated.

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In every case that I have had a problem with a CC it was the vacuum servo or vacuum control unit (under hood with vacuum lines.....forget the proper nomenclature without looking up).  I would visit the local wrecking yard and purchase a used unit (inexpensive and easy to replace).

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The cruise unit is pretty reliable,  so the first thing to check is the vacuum lines.   Without a steady vacuum,  the unit will not work, and it is cheap to check them.

There is a large hose that runs from the engine to the brake master cylinder.........where it attaches at the engine is the vacuum source......you will see a small line going back to the firewall that "T"s and one line goes to the passenger side, the other comes around

and goes to the cruise unit.    Check all those lines also check the fitting at the engine, sometime it cracks,  you can use carb cleaner or starter fluid to check for leaks, with the engine running, spray the fitting and lines,  if the engine speed changes you have found the problem.   Last....next to the brake pedal, there is the stop light switch and the vacuum dump valve......a defective dump valve can also be a problem.

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With the vacuum issues the cruise light should still come on just not engaged?  If the cruise light does not come on when the cruise switch is turned on it is more than lightly electrical? 

 

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Just an update:  

I haven't had a great deal of time to work on this, but I did do some preliminary checking.

The vacuum lines are completely toast.  They are baked enough that black chalk comes off in your hands when you touch them.  I have replacements and will be replacing them before doing more troubleshooting.

I suspect that it isn't just the vacuum lines because the "Cruise" light doesn't come on.  Either way, I would be at a stopping point when I got to the vacuum lines anyway.

 

Thanks for all of the replies!

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Replaced the vacuum lines and tested the servo (http://reattaowner.com/roj/component/content/article/index.php?option=com_content&view=article&catid=62:other-electrical&id=233:cruise-control-servo-electrical-testing)

The servo is bad.  I should have the replacement installed some time this week.

 

I've only had this car for a couple of months and I need to make sure I focus on one repair at a time.  As soon as I tear something apart, I see something else that isn't "quite right".  

It's like I'm chasing squirrels...

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Good decision to do one project at a time.   Sometimes you do several things and then if it doesn't run right......you don't know what might be wrong. 

 

I have been working on a 1965 Corvair for several years......did not intend for it to take that long but "more important things" caused the delay.

I am wrapping up the brakes and discovered when I converted it to a dual master cylinder,  I failed to plug an unused port.   It was in a difficult place to see....but I had a big leak.

With the port plugged,  I hope to have the brakes flushed and checked out and maybe drive it around the block soon

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I'm trying to maintain the car as a daily driver during the week so that I can do larger projects on other vehicles.  I'm pretty sure that's the only thing that stopped me...   

 

@Barney Eaton:  Good luck on the Corvair.  Not sure if there's a place on this forum for off-topic pics, but post something once it's back on the road!

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Success!  I replaced the servo (terminals C--> E measured open on the old one, @nic walker was right) and replaced the vacuum lines.  

Everything works as expected.

 

Thanks for all of the help!

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