89 Cruise Control Troubleshooting

[oleskool]

My truck has cruise but nothing happens when I turn it on. Where should I start looking?  Thanks for any help. 

[eaglescout526]

Oooo my area haha. I recommend checking the vac lines first. Once those are known to be good, check the switch that goes behind the brake pedal and make sure it is adjusted right(two man job). After that we will need to check electrical. 

[oleskool]

2 hours ago, eaglescout526 said:

Oooo my area haha. I recommend checking the vac lines first. Once those are known to be good, check the switch that goes behind the brake pedal and make sure it is adjusted right(two man job). After that we will need to check electrical. 

Awesome. For the vac lines. Any good schematics to look over. These are new to me lol. 

[eaglescout526]

I’ve got a NOS one I could take a pic of haha. But what I can tell you is this. There are four vac lines that run to the vac reservoir (football) behind the bumper. Two are for the HVAC and two go to CC. I don't know which ones are which as they can easily be plugged in either way on the football, but you will probably have to do some jiggling of the vac lines to see what is what. Follow one line from the servo and back to the football while the other line should meet where the HVAC gets it’s vac from. The second hose connected to the servo is with the CC wiring harness and it goes into the firewall and is plugged into a vac dump valve behind the brake pedal. 

[cruiser54]

[oleskool]

Awesome. Thank you both. All the HVAC works so I’ll see how I can track 

down the lines to know what is what.