Author Topic: Speedometer - why wires?  (Read 235 times)

Offline Mr Diesel

  • Registered Users
  • *
  • Posts: 173
Speedometer - why wires?
« 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?
1976 C20 CC, 6.2L SM465
1982 K30 CC, 427TD TH400
1983 C30, 6.2L TH400
1983 K30 CC, 454, 700R4

Offline MIKE S

  • Newbie
  • Posts: 20
  • Newbie
Re: Speedometer - why wires?
« Reply #1 on: February 07, 2019, 06:54:13 PM »
Should be speed sensor to ECM input for transmission and cruise control if equipped.   

Online bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5072
Re: Speedometer - why wires?
« Reply #2 on: February 07, 2019, 07:37:17 PM »
See below.  IIRC wire colors are red, green, black.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Mr Diesel

  • Registered Users
  • *
  • Posts: 173
Re: Speedometer - why wires?
« Reply #3 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!
1976 C20 CC, 6.2L SM465
1982 K30 CC, 427TD TH400
1983 C30, 6.2L TH400
1983 K30 CC, 454, 700R4

Offline hatzie

  • Site Supporters
  • Junior Member
  • ******
  • Posts: 764
Re: Speedometer - why wires?
« Reply #4 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
« Last Edit: February 10, 2019, 08:45:31 AM by hatzie »
SVC & wiring mans --> Here http://tinyurl.com/7387BRD-SVCMAN or My Bucket @ http://tinyurl.com/SQ-SVCMAN
Parts & Illustr Books -->http://tinyurl.com/SqParts
GMSTG Textbooks-->http://tinyurl.com/STG-TEXTBK
Radio Manuals-->http://tinyurl.com/DELCORADSVC

Offline Mr Diesel

  • Registered Users
  • *
  • Posts: 173
Re: Speedometer - why wires?
« Reply #5 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.
1976 C20 CC, 6.2L SM465
1982 K30 CC, 427TD TH400
1983 C30, 6.2L TH400
1983 K30 CC, 454, 700R4

Offline hatzie

  • Site Supporters
  • Junior Member
  • ******
  • Posts: 764
Re: Speedometer - why wires?
« Reply #6 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.
SVC & wiring mans --> Here http://tinyurl.com/7387BRD-SVCMAN or My Bucket @ http://tinyurl.com/SQ-SVCMAN
Parts & Illustr Books -->http://tinyurl.com/SqParts
GMSTG Textbooks-->http://tinyurl.com/STG-TEXTBK
Radio Manuals-->http://tinyurl.com/DELCORADSVC

Offline Mr Diesel

  • Registered Users
  • *
  • Posts: 173
Re: Speedometer - why wires?
« Reply #7 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.
1976 C20 CC, 6.2L SM465
1982 K30 CC, 427TD TH400
1983 C30, 6.2L TH400
1983 K30 CC, 454, 700R4