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73-87 Chevy _ GMC Trucks => Interior & Equipment => Instrumentation => Topic started by: Mr Diesel on February 07, 2019, 06:30:16 PM

Title: Speedometer - why wires?
Post by: Mr Diesel on February 07, 2019, 06:30:16 PM
Doing a bunch of re-wiring on my 1983 K30, trying to remove and fix a lot of the previous owner wiring hack jobs. Pulled the instrument cluster and discovered factory wires attached to back of the speedometer. Can't tell where they go, and my Haynes manual wiring schematic wasn't much help. Did GM use this for the cruise control or something?
Title: Re: Speedometer - why wires?
Post by: MIKE S on February 07, 2019, 06:54:13 PM
Should be speed sensor to ECM input for transmission and cruise control if equipped.   
Title: Re: Speedometer - why wires?
Post by: bd on February 07, 2019, 07:37:17 PM
See below.  IIRC wire colors are red, green, black.
Title: Re: Speedometer - why wires?
Post by: Mr Diesel on February 08, 2019, 05:48:05 AM
 I suspected it was for cruise control, but until now thought the original cruise system was entirely mechanical with no electronic portion.

That picture above matches exactly, and the wire colors are red, green, black.

Thanks for the replies!
Title: Re: Speedometer - why wires?
Post by: hatzie on February 10, 2019, 08:43:12 AM
This is the GM Service Training Textbook for the Cruise III systems.
If you intend to revive the cruise control it'll answer some questions about how that system worked.
http://www.mediafire.com/file/j5cws4inxl5q853/1984_CRUISE_III.pdf/file (http://www.mediafire.com/file/j5cws4inxl5q853/1984_CRUISE_III.pdf/file)
Title: Re: Speedometer - why wires?
Post by: Mr Diesel on February 10, 2019, 03:01:24 PM
Thanks for the link. Very useful information. I saved it to print out later because I would like to get original cruise working again some day.
Title: Re: Speedometer - why wires?
Post by: hatzie on February 11, 2019, 02:08:45 PM
Depends on what's knackered whether it's worth fixing Cruise III. 
It didn't have a stellar reputation for reliability and the parts are not cheap.

You may find it's easier and more cost effective to install a Rostra unit or a GM Electromotor cruise from an early 90's T400 truck or F-body.
Title: Re: Speedometer - why wires?
Post by: Mr Diesel on February 12, 2019, 09:13:11 AM
I think I have all the spare parts to make it work again. The truck actually had an aftermarket cruise system installed already and the manual for it was in the glove box so I could fall back on it too.
My wife's 1987 camaro has the original cruise control system still intact and it works as good as any new car I've ever driven.
Title: Re: Speedometer - why wires?
Post by: Johnret on February 04, 2020, 06:17:38 AM
What aftermarket Cruise System does it have?