Problem with cruise control- not working
Thread Starter
Staging Lane
Joined: Feb 2009
Posts: 69
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Problem with cruise control- not working 
I have a 64 Chevelle with a 2000 Chevy Tahoe 5.3L. I installed all the parts that I assumed I needed, and found that I had some issues with my installation. So recently I went and found all the pertinent diagrams and reworked my system.
For the Cruise switch, I am using a stalk from a 1979 Cadillac Seville and a rocker switch to turn the system on. The Chevy cruise control switch was a normally open style, and the stalk I am using is a 3 wire normally closed switch, so I need to use two relays to change the NC switch to NO switch. I used two 5 pole relays that have a NC and a NO pole that were energized when the system was turned on, and when the buttons are pushed (opening the corresponding switch on the stalk) they were de-energized swapping over the relay to the NC pole. I have used the check list from (I cant find the link now) and verified that I had power on and off when I was supposed too. I am attaching some links to make it easy for you to cite in trying to help me figure out why my system wont work. I have my wiring diagram (PDF), one for the Cadillac and two for the Tahoe. Let me know if you see anything wrong. I did find a diagram where Digital Dakota and there #3 stalk used two relays, one was NO and the other NC, and the green wire from their switch went to both of the relays. I dont think that applies to me, but could be an issue. I thought I had it all set, but it isn't working.
If that is the lever that just has resume and set in it then i am familiar with that cruise lever, but have never used one. However, what I would do is swap out the internal switch with a 4 wire switch. While you have the cover off, all you would have to do is slot it a bit so that the on/off portion can be utilized. If you're not positive it's out of a 79, then it may already be a 4 wire as they changed in 81 I believe. If you pop the cover off and it has the on/off function then it's a 4 wire and could be why your cruise isnt working, you would essentially have it wired backwards with the relays. I can walk you through swapping the switch if it sounds too complicated, but really it's easier than it sounds.
Last edited by ls1nova71; Aug 1, 2020 at 05:07 PM.
Thread Starter
Staging Lane
Joined: Feb 2009
Posts: 69
Likes: 0
If that is the lever that just has resume and set in it then i am familiar with that cruise lever, but have never used one. However, what I would do is swap out the internal switch with a 4 wire switch. While you have the cover off, all you would have to do is slot it a bit so that the on/off portion can be utilized. If you're not positive it's out of a 79, then it may already be a 4 wire as they changed in 81 I believe. If you pop the cover off and it has the on/off function then it's a 4 wire and could be why your cruise isnt working, you would essentially have it wired backwards with the relays. I can walk you through swapping the switch if it sounds too complicated, but really it's easier than it sounds.
On one of the posts I found, I saw one of the guys had a Digital Dakota 4 wire switch, but not sure if it is a NO or NC switch or a combination of the two. It had one of the relays set up as a NO and one as a NC. I will try to find the diagram and post it. See what you think between the two.
This one is a little different than mine.
Thread Starter
Staging Lane
Joined: Feb 2009
Posts: 69
Likes: 0
I had found your post from 2016, and followed the flow chart, all checked out. Here is what you had posted:
Unplug the harness side of the TAC module, and with the ignition ON and the cruise switch set to ON, using a test light, test for power between pins 14 and 15. If it lights up go to the next step.
With ignition ON and the cruise switch set to ON, using a test light, test for power between pins 15 and 6. It should NOT light up, now press on the brake pedal, it should now light. If it lights, go to the next step.
With ignition ON and the cruise switch set to ON, using a test light, test for power between pins 15 and 4. It should NOT light up, now press the set/coast button, it should now light up. If it lights go to the next step.
With ignition ON and the cruise switch set to ON, using a test light, test for power between pins 15 and 5. It should NOT light up, now press the resume/accel button, it should light up. If it lights up, go to the next step.
Unplug the C2 plug on the PCM (blue), and with the ignition ON, check for power on pin 33, should light up."
Unplug the harness side of the TAC module, and with the ignition ON and the cruise switch set to ON, using a test light, test for power between pins 14 and 15. If it lights up go to the next step.
With ignition ON and the cruise switch set to ON, using a test light, test for power between pins 15 and 6. It should NOT light up, now press on the brake pedal, it should now light. If it lights, go to the next step.
With ignition ON and the cruise switch set to ON, using a test light, test for power between pins 15 and 4. It should NOT light up, now press the set/coast button, it should now light up. If it lights go to the next step.
With ignition ON and the cruise switch set to ON, using a test light, test for power between pins 15 and 5. It should NOT light up, now press the resume/accel button, it should light up. If it lights up, go to the next step.
Unplug the C2 plug on the PCM (blue), and with the ignition ON, check for power on pin 33, should light up."
I remember posting that, but had forgotten all about it. Lol! Anyway, if everything checked out, then you should have the switch/relays wired up correctly. Most aftermarket switches are NC, so you could try wiring it like the last pic, but it doesn't seem like that is the issue. Do you have LED brake lights?
If its wired right and you have regular light bulbs in the brake lights then it should work. You might try adjusting the brake light switch itself so that you have to press the pedal a little further to make the lights come on. I have seen instances where the two sets of contacts in the switch aren't quite "synced". I am assuming you have a GM 4 prong brake light switch though.
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