I solved a cruise control problem

[67 Burb]

I thought I'd pass on some information about a problem that showed up because of one too many aftermarket gadgets added to my Burb.

I installed an aftermarket cruise control on the Burb which had one wire connected to the brake light switch. (on the light side of the switch.) This is to disengage the cruise when the brake is applied.

A couple of months later, I made up some LED tail lights and installed them on the Burb.

On my next road trip, I found that the cruise didn't work. After checking the fuse and all of the electrical connections as well as all mechanical parts of the cruise, I got thinking about what had changed since installing the cruise control. All that had changed was the addition of the LED tail lights.

I had always assumed that the cruise disengaged when it got voltage from the brake switch, but realized that the cruise will work only when it is grounded through the brake light bulbs. When the brake pedal is pressed, the light side of the switch goes high (it's no longer a ground because it is now positive).

Well, the cruise controller can't get a ground through the LEDs, so it would not engage because it thought the brakes were applied. To solve the ground (or lack of it) problem, I connected a relay to the brake switch, with the wire from the cruise controller grounded through the normally closed relay points. Now the cruise has it's ground, and when the brakes are applied, the relay points open, the cruise loses it's ground, and disengages.

Problem solved!

Bob (Sorry if I was too long-winded)