Cruise Control Issues
Burning Brakes
Joined: Jun 2014
Posts: 1,020
Likes: 51
From: Connecticut
It could be the speed converter or the servo. What happening is what I went thru a long time ago. Mine was the servo two times and once it was the brake switch.
But what happens is the speed gets outside what the cruise can handle so it shuts off. As mentioned that could be it sensing the speed changing radically for a split second or the servo not responding the way it should.
But what happens is the speed gets outside what the cruise can handle so it shuts off. As mentioned that could be it sensing the speed changing radically for a split second or the servo not responding the way it should.
I don't know how this speed converter actually works but I assume it takes the VSS signal and up converts or down converts the signal IOT compensate for a (assumed) gearing change. If this box has become intermittent (signal jumps, has has a high noise floor or is failing) then the CC will try to compensate to follow the driven VSS signal. It could also be a bad installation as well (bad wire crimp or loose wire).
If it is the servo, then the servo is over correcting the throttle control cable and is setting up an oscillation due to over correcting and compensation. In other words the car speeds up too much and the system has to correct the issue by slowing down. Which it corrects by slowing down too much (over correction). IOT fix this problem the system speed up again but again it over compensates and so on back and forth within the limits of the system until the operator cancels the CC or the system faults and drops off. This is the same type of issue you would see with an overly slack or overly tight throttle control cable.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
Bill, take a look at these "Super Chevy" articles for troubleshooting a Cruise control system, you'll notice in the one article that the Cruise control module is a stand alone unit after the model year 1989, and although there are no trouble shooting procedures giving for this unit, it has been mentioned they rarely fail.. For what it's worth!
http://www.superchevy.com/how-to/add...ottom#cxrecs_s
http://www.superchevy.com/how-to/820...ottom#cxrecs_s
http://www.superchevy.com/how-to/add...ottom#cxrecs_s
http://www.superchevy.com/how-to/820...ottom#cxrecs_s
Thread Starter
Burning Brakes
Joined: Jul 2014
Posts: 801
Likes: 31
Bill, take a look at these "Super Chevy" articles for troubleshooting a Cruise control system, you'll notice in the one article that the Cruise control module is a stand alone unit after the model year 1989, and although there are no trouble shooting procedures giving for this unit, it has been mentioned they rarely fail.. For what it's worth!
http://www.superchevy.com/how-to/add...ottom#cxrecs_s
http://www.superchevy.com/how-to/820...ottom#cxrecs_s
http://www.superchevy.com/how-to/add...ottom#cxrecs_s
http://www.superchevy.com/how-to/820...ottom#cxrecs_s
Is there CC computer?
Melting Slicks
Joined: Jun 1999
Posts: 2,931
Likes: 127
From: Ashland Alabama
All gm vehicles that use that servo provide on/off/reference pulse basically.
It wont work under x pulses which is to prevent engaging at to low a speed aka under 35 mph but since it doesn't actually know how fast your going its done by pulses which are provided by a vss box. Im not sure exactly how the vette does it but luckily the same unit was on my trans am which I built all the electrical stuff in
On the t/a theres a yellow vss box that handles converting the speed signal form the transmission to what the speedometer and cruise uses.
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Advanced
Joined: Dec 2006
Posts: 53
Likes: 0
From: Newton KS
The cruise in my 85 acts just like yours. At 55 MPH the cruise isn't usable, at 75 MPH it is better but not right. Over the past 10 years I have tested and retested everything, even pulling the instrument cluster out. Everything checks perfect. When I first got the car, I swapped in a TKO transmission and used an Abbott box to calibrate the speedometer. I have questioned if the Abbott box was the problem but never saw any other complaints.
billy mild you need to check the wiring starting at your VSS to see how it was done. If the connections aren't soldered that could be your problem.
Thread Starter
Burning Brakes
Joined: Jul 2014
Posts: 801
Likes: 31
I finally fixed my cruise control! After reading on Mustang and diesel truck forums I had an idea of the fix. I then E-mailed Abbott and they agreed. When I installed the ERA box, I used a weather pack connector between the car and the ERA. This wasn't a good enough connection, so I had to cut the connector out and crimp/solder/heat shrink the wires from the VSS to and from the ERA box. I took the car out and the cruise works like it should.
billy mild you need to check the wiring starting at your VSS to see how it was done. If the connections aren't soldered that could be your problem.
billy mild you need to check the wiring starting at your VSS to see how it was done. If the connections aren't soldered that could be your problem.
Advanced
Joined: Dec 2006
Posts: 53
Likes: 0
From: Newton KS
The instructions that came with my ERA 10 years ago says that the red wire is "12 volts, ignition on". I eliminated the cigarette lighter from the console and might have used that wire for power.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The cigarette lighter is powered all the time so that wouldn't be a good choice for this application.