I was thinking about getting LED bulbs. Why do you have to rewire the cruise control?

Nice job you did. I got lucky with my 89 Regal lights, there are no cracks. I took them off to paint the coach.
Question: did you find that the Barth factory left very short wires to work with, and used a couple of yellow wire nuts too? I was surprised to see Barth did a sloppy job.

quote:

Originally posted by Jeff S.:
I was thinking about getting LED bulbs. Why do you have to rewire the cruise control?

Most cruise controls have a brake sense wire which requires a path to ground while engaged, ie through the bulb filament. When the brakes are used, the wire goes up to 12V, the bulb lights and the cruise will disengage.

With LED tail lights there is no path to ground when brakes are not energized, since they are diodes. Without the path to ground, the cruise will not engage.

No need to rewire really, just need to provide a ground path. This can consist of a 200 ohm resistor tied from a brake light wire to ground, or an extra dummy brake light bulb behind the tail light assembly.

LEDs can also cause problems with turn signal flashers. Some flashers are load dependent and will not flash correctly unless they have full load through the bulbs. With the LEDs the load is much less and the flashers may not work, or cycle slowly. There are flashers available which are not load sensitive. Also, the dummy bulb trick can be used instead.

My experience showed that the Barth coach wiring was quite adequate but the GM chassis wires were very marginal. There are threads here describing modifications to headlight wiring to get full brightness. My Regal headlights had barely 11V when lit. Heavier wires help. OTOH, if LED headlights are installed, their lower current demand allows full brightness with original wiring.

Wire nuts are probably not OEM. As with all old vehicles, particularly those in corrosive environments, it is prudent to check all exterior connections, especially chassis ground connections. For me, soldering is the gold standard but crimps and heat shrink tubing are pretty good too.