Cruise Control woes

[CyberSniper]

84K10 with cruise control and delayed wipers. It has the electronic eye thing that goes in the back of the speedometer.

I searched and found some info... but not what I was looking for. Please bear with my stupidity found below. I've been trying to chase down this cruise control problem for months.

So far I have swapped out the module (the thing above the accelerator pedal) and tested/swapped out the vacuum/electric switch that goes next to the brakelight switch.

The smartstick/stalk was replaced 6 months ago because it was believed to be bad and it was replaced a month ago and I don't think it was bad either. I'm going to replace it again tomorrow.

I hooked up a solenoid temporarily and drove it down the road just in case mine is bad. The solenoid doesn't appear to ever get power to it.

The speed buffer thing... I think I've replaced that once and it didn't do anything. Should I try it again? I'm sure I have another one laying around somewhere.


Does anyone know what wire(s) should have power to it? At what times? Where it gets its power from? My manual is as useless as a screen door on a submarine when it comes to cruise control. I figured I'd give tracing wires a whirl but there is a buttload of wires to trace. A schematic would be very nice because then I could make sure all of them were working without following them physically.

 

[dyeager535]

this help at all?
should be '86 cruise diagnosis

Throwing parts at problems is expensive. Did you ask here first?

 

[CyberSniper]

I searched here first. I tried all the stuff everyone else had problems with before I asked (there are a lot of cruise control posts in the archives). I only have 28.8kbps here at my parents' and it makes using the computer rather painful when you're used to 2mbps cable.

I haven't actually bought any new parts yet for the cruise control system. I did throw money needlessly at the delayed wiper switch in the column while I had it completely disassembled (didn't want to have to pull the column apart again if it went bad). I have an 87 C10 I've been robbing parts off to swap plus I have a bunch of other parts off other cars I've been trying. The only hard to replace thing is the solenoid back there by the distributor which is why I only plugged a different one in instead of trying to replace it.

I'm going to swap out another stick and see if that solves the problem.

I looked at your website and I'd like to give that a try but I don't know which terminal corresponds to which wire. I have two scanned images called "34-0.jpg" and "34-1.jpg" that go to a car, do you know if the terminals/wire colors are going to be the same?


Thanks for your help
-Brian

 

[dyeager535]

Kind of tough to tell the wire colors Brian. The VSS buffer (light blue or yellow box) uses different wiring diagrams when in a CCC system (all carbed GM cars 1981+) than it does in a truck without CCC, so they could most definitely be different.

The three wires running to the speedometer so far all seem to be identical. I'm not sure if you knew this or not, but the plugs, and sometimes the piece they plug into, typically have the terminal number or letter cast into them. Thus, on the diagram I linked you to, "R" SHOULD be marked on the connector or component, so wire color is irrelevant. Wire routing SHOULD be similar to the vacuum solenoid on a car or truck regardless of wire color, but depending on year and application, there is always the slight possibility that something changed.

 

[CyberSniper]

I didn't get nearly as far as I thought I would today. I know I have a good smartstick. I know I have a good brake switch. I know I get power to the system (to the stick and the module).

I'm no longer sure if the solenoid/servo box is good (but what is the chance of having two bad ones?) and I'm not so sure if the module is good either. I pulled apart all my cruise control modules and all of them are different inside so I guess i can't run any other ones except the one in my truck and know it should work.

Does the thing that plugs into the back of my speedometer ever go bad? I'm leaning towards the buffer box now but even though I have a bunch of them (the one in my truck is yellow) I don't think I can trust that they're all the same.

Usually I can track down gremlins pretty quick but nothing appears to be broken. My cruise magically quit working when I removed the ESC computer but that has nothing to do with cruise control. I attribute it quitting to the smartstick's "resume/accelerate" function dying (yellow wire). Between the butchering the PO did for the plow and all the crap I've added under the dash the whole area is a nightmare. It wouldn't be so bad if I didn't have AC.

I'm going to look for any unhooked ground wires tomorrow. I'm also going to try to test the module using the stuff you gave me. I'm probably going to pull the cluster to make sure the pickup is still attached to the speedometer and then see if the speed buffer is still plugged in. After that I'm kind of at a loss.

 

[dyeager535]

If lockup works on your truck, the buffer should be good. Not sure how a bad buffer actually affects the TCC system, but I KNOW it governs the low-speed lockup. (mine wouldn't lock under 35MPH)

The buffers should never really go bad, it's just a printed circuit board with a few components on it. I'm sure they can, it's not common at all though.

Above is incorrect, in a non-EFI/CCC vehicle, lockup is controlled via vacuum.