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notfrommensa
07-30-2011, 01:21 PM
2003 Pontiac Grand Prix:

On a recent long road trip, my Cruise Control crapped out about 3 hours from home at about 8 pm (on the return home). ugh. reset, and it would work for about a mile, and then shut down. Rinse, lather, and repeat.

I am about to embark on another long road trip, so I am looking to troubleshoot the problems on my CC. and I think I have a possible root cause after a cursory google search. I think it is the combination of the both the headlights and the cruise control on at the same time.

I went out this morning to test my theory. Go on the nearest stretch of low traffic, straight road and engaged the Cruise control. it worked, never shut down for about 5 miles. Turned around, turned on headlights, cruise would work for a minute and then shut down. Rinse lather a repeat.

So what could be happening? Overloading a fuse? A circuit? Is there a short in the brake switch that is only activated? something else that I am not thinking about?

thelabdude
07-30-2011, 02:19 PM
I find the electrical system in my 02 Cavalier insanely complex. I am sure your 03 GP is the same. Aside from some general checking of connections and voltage levels, I am not sure what to do. I think some of the consumer grade auto parts, i.e. Auto Zone will read codes for you.

jasonh300
07-30-2011, 03:48 PM
Could a crossed exposed wire be causing your taillights to backfeed into the brake light circuit? If the brake light circuit gets energized, it'll kill the cruise control, just like tapping the brakes.

Rick
07-30-2011, 04:08 PM
Without a wiring diagram all any of us can do is guess.
Here is mine:
Go into the trunk and locate the ground connections for the tailight assemblies. Take them apart use some fine sandpaper and make sure they are clean then reassemble good and tight. Also make sure you brake light bulbs are good.
Many cruise system ground through the brake light bulbs and bad bulbs or a bad ground at the taillight can cause a CC malfunction.

Al Bundy
07-30-2011, 04:55 PM
Unlike vehicles of yesteryear, today's vehicles often use the same circuits for multiple devices. There is the possibility that the ground side of that circuit is not very good. The lights take the big amps and the CC is getting squeezed out. Tracing out the bad ground can be difficult without a diagram or experience. It might be easier to add extra ground wires instead. You cannot damage anything by duplicating a ground wire. Just make sure it is the ground you are working with or you could see smoke.

jasonh300
07-30-2011, 10:45 PM
Unlike vehicles of yesteryear, today's vehicles often use the same circuits for multiple devices. There is the possibility that the ground side of that circuit is not very good. The lights take the big amps and the CC is getting squeezed out. Tracing out the bad ground can be difficult without a diagram or experience. It might be easier to add extra ground wires instead. You cannot damage anything by duplicating a ground wire. Just make sure it is the ground you are working with or you could see smoke.

I have to disagree with this. Vehicles of yesteryear might have had 5 circuits throughout the entire vehicle. Todays cars might have 30 or 40. Of course there are many more electrical accessories nowadays.

california jobcase
07-30-2011, 11:03 PM
It could be a small vacuum leak, if that car's cruise control servo is vacuum operated.

Full Metal Lotus
07-30-2011, 11:05 PM
One thing, non electrical to check is your vacuum line and its connection to your CC, this sound like it could be a slow leak. The co-relation with the headlights could just be a fluke.

(Had a vac leak with an early Honda CC do exactly what you described, except for headlight issue.)

Good luck!

notfrommensa
07-31-2011, 10:17 AM
Thanks guys, does it take a mechanic to check vacuum, or can I (a novice) do anything? At this point, I am hoping for a headlight correlation. Headed out tomorrow. I am not planning on driving at night.

chaoticbear
07-31-2011, 12:32 PM
This is going to sound terribly dumb, but is the cruise control control in the same lever as the lights? This was the case with my previous car, and the cruise control would only work when the lever was pulled back slightly (not quite enough to activate hi-beams), so on long trips, I'd wad up a piece of napkin or paper towel to wedge the lever forward a bit. Just another harebrained theory.

jasonh300
07-31-2011, 02:13 PM
Thanks guys, does it take a mechanic to check vacuum, or can I (a novice) do anything? At this point, I am hoping for a headlight correlation. Headed out tomorrow. I am not planning on driving at night.

Does your car have little doors that cover the headlights when they're turned off? The last car I saw those on was a 90s Oldsmobile, but the doors were vacuum controlled.

kanicbird
07-31-2011, 02:36 PM
It sounds like some fault in the taillights backfeeding to the brake light particularly for dual filament bulbs. Also possible if the headlamps + turn signal is in use.

First I would check that the bulbs are all working, then make sure they are grounded OK.

A conversion to LED taillights may also help but it's a long shot and really only mask the problem.

thelabdude
07-31-2011, 03:44 PM
Does your car have little doors that cover the headlights when they're turned off? The last car I saw those on was a 90s Oldsmobile, but the doors were vacuum controlled.

I have been wondering about that too.

Rick
07-31-2011, 04:09 PM
It sounds like some fault in the taillights backfeeding to the brake light particularly for dual filament bulbs. Also possible if the headlamps + turn signal is in use.

First I would check that the bulbs are all working, then make sure they are grounded OK.

A conversion to LED taillights may also help but it's a long shot and really only mask the problem.
See post #4 :D

notfrommensa
07-31-2011, 06:28 PM
No fancy headlight covers for my cheapo Grand Prix.

notfrommensa
08-01-2011, 09:34 PM
And I can definitely say the CC is definitely headlight related. they never crapped out on my 550 mile trip to Appalachia. Not one time. I didn't drive at night nor did I ever turn the lights on, didn't want to tempt fate. I did notice another problem, when the brakes were tapped, the radio light dimmed as well as the little red indicator that tells what gear shift is on. Something is amiss with the electrical system. Probably an easy fix or a really hard fix.

thelabdude
08-01-2011, 09:44 PM
I had an 81 Phoenix with some electrical gremlins. The dealer wasn't much help as long as he lasted. The night I bought the car, the dealer said a few more deals like this and I am out of business. Six months later he was.

One of the biggest problem was when I would hit a bump, the windshield wipers would take a swipe. One guy suggested only driving on smooth roads. He was unable to point me to any when I asked. After a few years, I came across a loose screw holding a ground wire on the underside of the dash. It took longer to get a screwdriver than it did to tighten it. Problem solved. Many dumb problems like that take a lot longer to find than fix.

Maybe if you kick it on and off as fast as you can, you will see some smoke.