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Discussion Starter #1
Inspired by a review of the Evora S in this morning's New York Times, which mentioned that the test car had a malfunctioning cruise control, I thought I would pass on a couple of tips for those who find themselves having the same problem.

The Evora's cruise control, like all modern cars, relies on the drive-by-wire system built into the throttle control; in other words, no additional mechanical parts are required for cruise control beyond a pair of control switches. (See this thread if you are interested in adding cruise to an Evora that did not come equipped with it from the factory.)

In reading this board-- and, embarrassingly for the factory, a couple of magazine reviews-- it seems there are occasionally problems with the cruise control installation, despite its simplicity. Fortunately, the solutions are simple, and don't require a trip to the dealer.

The problems are of two types: the cruise control turns on and off normally but fails to hold speed after going over bumps in the road; or the cruise control behaves erratically, sometimes failing to switch on (no indicator on the dashboard), sometimes failing to take a speed setting, sometimes switching itself off entirely (dashboard indicator goes out).

I'll describe the two problems, and their fixes, in separate posts for convenience.
 

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Discussion Starter #2 (Edited)
The first problem: dropping out over bumps

The first problem has to do with a sensor on the clutch pedal. This GM item consists of a rotary potentiometer with a slotted plate that contacts a post on the shaft of the clutch pedal assembly. When you step on the clutch, the plate is pushed by the post, which rotates the sensor. This tells the computer that the clutch is being depressed, and also how far. (This has other uses besides the cruise control.)

Cruise control, for obvious reasons, must be interrupted when the clutch or brake is pushed. What may sometimes happen is that that the clutch sensor is too sensitive: it thinks the clutch is being pushed, when in fact it's only been slightly joggled as you drove over a cat's eye or pavement seam. So we need to adjust the position of that sensor to make it just a little less touchy.

There are two ways to adjust the sensor's position. One is loosening the bolts that hold the sensor's mounting arm and trying to wiggle the arm to a lower position so that the center shaft of the sensor is closer to the clutch arm post. I do not recommend this approach, as it is more difficult and less effective than the other way: simply bend the slotted plate on the sensor very slightly.

Reach under the dash and follow the arm of the clutch pedal up until you can feel the slotted sensor plate. (Hold your fingers in a V-for-victory and then stick the index finger of your other hand in between. The V is the slotted plate, the other finger is the clutch arm post.) The plate is simple raw nylon, a translucent yellowish plastic that bends nicely as long as you're careful.

If you have trouble picturing this, go stick your head under the dashboard.

The plate is flat, with a plane inline with the car's axis. Both fingers point down, thus one finger is closer to the front of the car. Gently bend that finger forward just a bit. You'll feel it flex. Hold it for a moment or two until it takes a bit of a set. And that's it: you're done. Because the movement of the pedal is so slight over a bump, you only need to bend the slotted plate very slightly.

Take it for a test drive. If it's anything like my car, you have fixed the problem. I have done this twice, with six thousand trouble-free miles in between.

Rumor has it that GM has come up with a better replacement part that doesn't require these "adjustments", but I believe this part is for an Opel/Vauxhall not sold in the US, I can't say for sure.

Next, the more serious cruise control problem... also easily fixed, but you'll need tools this time.
 

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Discussion Starter #3
The second problem: won't turn on, won't turn off, won't stop turning on or off

The second problem with cruise control has to do with the switches in the steering wheel. That's right-- the only other parts in the system!

This is a funny problem, because your dealer will simply throw parts at it without solving the issue for more than a short time. This is where dealer mechanics, and the constraints of their business model, really fail: you can't just screw in a new part, because the problem is the part itself.

First, the symptoms: you start to notice that sometimes, maybe after working fine for a while, the cruise control fails to turn on when you hit the button. Other times, it might fail to turn off, or fail to set a speed, or etc. You probably also get an intermittent "wrench light" in the dash after startup which, since you have read your owner's manual (ahem), you know indicates an electrical malfunction. Your dealer tells you the computer says the cruise switch/switches is/are bad. Very odd, because they're new. Hmm...

The cruise control switches are simple and robust microswitches that mount with two screws each into the steering wheel's frame. (See our friend from Oz's photos in the how-to-add-cruise thread referenced above.) A short and simple wiring harness then connects the switches to the "clockspring" connector at the steering column.

What could go wrong with such a simple assembly? One thing: connections.

Now, in order to perform the fix I outline below, you have to mess a little with the airbag. It is important to understand that airbags are explosive and could kill you. Sitting in the driver's seat with a set of pliers in front of the airbag pointed at your chest is a bad place to be if that thing goes off. You have been warned: if you die because you read this post and did something stupid, your survivors have only you to blame (you idiot).

I myself have no kids and all my wives are exes, so I figured what the hell.

The airbag must be moved or removed to get to the cruise control switch connections. The airbag assembly is held on by two bolts accessible on either side of the forward part of the steering wheel, at the 3 o'clock and 9 o'clock positions. These are either hex or Torx heads, I forget which. Loosen and carefully remove the two bolts, holding the airbag from falling as you pull the bolts free. If the horn is honking now, it is reminding you that you forgot to disconnect the battery.

You can either unplug the airbag's connection to the "clockspring", or carefully leave the airbag nestled against the wheel, not hanging from its wiring of course. Now you will see the switches and the harness.

Grab the harness connector at the switch, either side, between thumb and forefinger. If it wiggles, you've found your problem.

My theory is this: The connectors were mis-specified or manufactured incorrectly with receptacles that are just slightly too large for the posts on the switch. So instead of making a solid electrical connection, they connect only intermittently when they shift.

Picture putting a small headphone plug into a large headphone jack. The plug is on the back of the cruise switch, the jack is the connector at the end of the harness.

My solution to this was to strap the harness connectors to the steering wheel frame with plain old cable ties. This pulls them against the switches' connectors, making a firm connection without placing undue strain. In other words, if you made a section through the connection, the harness connectors would be slightly tilted with respect to the switch. I'm sure there are more technical solutions, but this one has been solid for many thousands of miles now.

Might be hard to picture staring at your computer screen, but once you have the parts in front of you you'll see it's dead simple. Just watch out for that airbag, ok?

Hope this helps!
 

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Thanks for the information!

I haven't had any issues and I hope not too but at least now I can easily get to the bottom if something does!
 

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Damn...this is quite a write up! Thanks for doing this. Any quick pics?
 

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Yay - excellent write-up!

First, the symptoms: you start to notice that sometimes, maybe after working fine for a while, the cruise control fails to turn on when you hit the button. Other times, it might fail to turn off, or fail to set a speed, or etc. You probably also get an intermittent "wrench light" in the dash after startup which, since you have read your owner's manual (ahem), you know indicates an electrical malfunction. Your dealer tells you the computer says the cruise switch/switches is/are bad. Very odd, because they're new. Hmm...
I've just added another 2,200km to the car & spent in excess of 15 hours on cruise (Sydney to Melbourne return). I was starting to get these symptoms right at the end of the trip & was going to do just that...check the connections.

Us Evora owners need to be somewhat handy with a spanner. Torx bolts for sure, BTW...can't remember the size off-hand.
 

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I stopped using my cruise control because it would kick off over every tiny bump (about every 5 seconds). Figured I would let the dealer fix it next time I was in, but the finger bend thing worked great. It didn't kick off once in 80 miles today. Can't believe that bending it just slightly (it still springs back to touch the pedal) is enough to fix this.

Thanks West!!
 

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A quick question regarding the battery. If I disconnect the battery to check the connection in the steering wheel, what do I lose besides all the settings in the nav and radio, do I also lose my Homelink garage door settings? Is there anything else that must be reset with the ecu or other functions of the car? Can a very low powered 12 volt battery be hooked up to the plus and minus terminals when they are disconnected from the main car battery, this giving enough power to keep all the settings from being lost?

Thanks,
EFE EVS
 

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Fixed cruise problem!

Problem fixed!

As per W.O.H advice, I took the steering wheel apart first, then used a ohm meter to check the harness wiring and all associated cruise switches, all were making good connections but I used small tie wraps to secure the wiring against the steering wheel frame and tight against the sockets they're plugged into. That wasn't the problem though. Next, I inspected the clutch pedal and the rotary switch that is connected to it via a plastic fork, that was the problem.

I will vary a little from what W.O.H said and this will fix the problem so you'll never have to deal with it again.

Near the top of the clutch pedal arm, there is a 3/16 X 1 1/4 inch long shaft sticking out horizontally from the clutch arm and the shaft slides between two fingers of a plastic fork. Picture taking your right hand index finger and holding it in front of you horizontally, then take your left hand index and middle finger and place it over your right index finger as a cowboy's legs straddling a horse. When you press the clutch petal, that shaft rotates the fork which is connected to a rotary switch, that switch sends a signal to the cruise control. The rotary switch is mounted to a flat metal arm that is bolted to the firewall. The problem is, the plastic fork is right near the end of the 3/16 shaft and eventually slips off as if a horse rider was riding on the tail end of a horse and slipped off, he needs to be planted securely in the middle of the horse and not at the tail end. W.O.H suggested bending the plastic fork just a little so it is straddling the end of the shaft again. The problem with that is, that plastic fork will bend a little but it will only slip off again in time. The entire fork and switch and the mount they are attached to need to move over a good 1/4 inch so the fork is not near the end of the shaft but securely straddling it. As I stated already, the entire switch and fork assembly are mounted to a metal arm (or bracket) which is bolted to the firewall with two bolts. All you need to do is get your hand securely on that metal arm and bend it closer towards the clutch pedal, this will move the switch and fork into a position with the shaft going all the way through the fork and it will never slip off again. If any of you want to check to see if your fork is nearly slipping off the end of the shaft, just take a light and lay on your back under the drivers side dash. It's pretty simple to take your hand up to that mounting arm (bracket) and bend it towards the clutch pedal, this will position the plastic fork further onto the shaft so it won't slip off the end.


Thanks to all and to W.O.H for pointing out the two problem areas. I did not see any problem with the wires or connectors in the steering wheel, they looked to be a tight fit. Cruise control works great now! :coolnana:

EFE EVS :wave:
 
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