Adding Cruise Control To 1988 K1500

[Majoraslayer]

Several years ago I added cruise control to my 1988 K1500, using parts pulled from a junk yard. It never worked quite right, and eventually I figured out that I had incorrectly connected the speed signal to the cruise control module. Instead of the buffered signal it needs from the DRAC, I had directly spliced it into the VSS output from the transmission. When I realized the problem, I disconnected it from my VSS and abandoned the project. At the moment I have my truck apart working on an engine build, and have been working on cleaning up all of my wiring. I figured there's no better time to go back and try to fix the cruise control while I'm at it.

To a certain extent, my cruise control DID work, but it never correctly maintained the speed it was supposed to and wouldn't hold at the SET speed. Based on that, I'm going to say all of my other wiring for the cruise control system should be good, I just need to find a good speed signal to feed it. For those of you who have done this, where did you tap in to get the correct signal? I've seen several threads mentioning to tap into the DRAC output, but my understanding is that the DRAC on my model year is built into the gauge cluster itself.

Out of additional curiosity, for those of you who have cruise from the factory on an 88-91, do you have any kind of indicator light in your dash for it when you turn it on?

 

[AK49BWL]

No, GMT400 trucks never had a cruise indicator. I'm a little fuzzy on the 88-91 clusters, but I do know there's an output from the DRAC for the ABS module... It stands to reason there would be an output for the cruise module too.

Hmm, yep! Pin A16 and B17 are both DRAC outputs, B17 to ECM, A16 to the cruise module.

Actually A16 goes to the convenience center where you're supposed to plug in the various cruise control connectors in 88-94 trucks