I need help!

On my 1984 Royale (reallyl a Regal),I have this problem.

1. WITH the ignition on, my brake lights come on/stay on without depressing the brake pedal.

2. WITHOUT the ignition on, I can depress the brakelights and the brakelights operate normally. BUT, the headlights simultaneously light up as I push down the brake pedal...I'm guessing some kind of feedback from the brakelights to the headlights...

Turn indicators work fine.



Couple of other things...WITHOUT the ignition on, when I push the brake pedal, I can hear 2 different clicks.. what sounds like a relay activate up front behind the glove compartment area on the passenger side of the dash and I also hear somekind of relay activating toward the back of the coach also.....

O.K. Put those amazing minds to work and give me some theories...

K&E

Any trailer light recptical on this coach?

Doorman

As a general rule, the symptoms are that of a bad ground.

Interesting...

The circuits for brake lights and the headlights are normally "hot" without the ignition. Both will normally work without the ignition and should not be affected by it... or each other. Do the headlights come on full bright? The fuse block and other wiring is located under the panel in front of the brake pedal. Are there any wires near the brake lever that may have been snagged or pinched?

I think Rusty is on the right track, either a bad ground (or something grounded that shouldn't be) Question is... what, and most important, where?

I am assuming that your wiring is original. I don't think headlight or brake relays were originally installed. There may be a fuel tank selector relay that clicks on power up depending on which tank is selected, and maybe a relay for the electric fuel pump...

I have the GM wiring diagram for the 86 year (it's here on the site as well) The fuel system was changed in the 85-89 models and is likely a bit different. I'm looking for what is being changed by the ignition switch....weird. Like Arnold says, "I'll be back... "

quote:

Any trailer light recptical on this coach?

Yes there is a trailer connection on back...

another vote for checking grounds first.

I asked about trailer connector because on my GM van I had about the same problem. Found shorted contacts in connector. A 12v accsesory leg had shorted to a brake circuit leg,backfeeding brake circuit.

Doorman

I've spent some time looking at the 1986 GM wiring diagram. It should be fairly similar to yours for lights and ignition anyway. (see attachment below)

There are several good arguments for checking grounds.

1. You will notice in the center of the page there are a "sheet metal ground" and an "instrument panel ground" shown (circuit 150) These would be connections somewhere between the instrument panel and the adjacent chassis.

2. Your symptoms included the ignition switch. The switch is poorly drawn at the bottom of the
page, showing the switch in the 4 positions and which lugs are connected.

Notice that the switch has a normal ground symbol at the 11 o'clock position, and 2 other lugs labelled GRD 1 and GRD 2 near the top. Notice that these GRD 1 and 2 lugs are open (not connected) when in the OFF-LOCK position but connected when in the RUN position.

Since your symptoms change with ignition switch position I am suspicious of these 2 "GRD" wires. Unfortunately, you will also note that the ignition switch connector details are "N/A". The circuits are only identified by number, location, and wire size/color. I traced these back:

Circuit 2 (red) is the 12VDC from the fuse panel. (Thank God they're not all red! )
Circuit 3 (pink) is the power for the Ignition
Circuit 4 (brown) is the power for the ACC
Circuit 5 (yellow) goes through neutral switch to starter.
Circuit 150 (black) is the generic ground, like #1 above

This leaves us circuit 33 (tan/white) and circuit 130 (brown) left over as the unknown GRD 1 and 2.

Further inspection of the headlight switch and turn signal switch (just above the ignition switch in the diagram) shows nothing in common with the ignition switch except they share the same power and ground circuits (2 and 150, respectively) but no reason for 33 or 130 to affect the headlights.

Meanwhile, the brake switch involves circuits 140 (power) and 17 (stoplamp) Circuit 17 is found at the turn signal but not near ignition...

As you can see this is actually a wiring "diagram" not a true schematic. I attempted to follow circuits 33 and 130 to find out what the functions of the mysterious "GRD 1 and GRD 2" are with no luck. The circuit numbers change at the firewall plugs and I can't find them yet in the chassis prints.
I'm going blind and it's driving me crazy.

Bottom line is I can't yet explain your symptoms which include headlights AND brakes...

This much for sure: There are a couple of ground lugs in the panel somewhere to find and check connections. Also be sure the ignition switch is grounded and all the switch connections (esp smaller tan/white and brown wires) are good. As suggested be sure your trailer connector is OK, too. (This makes sense for the brake lights, but headlights???) still weird.
The rest of the diagrams are in the archives if you want a challenge!

Keep me posted if you have more info and symptoms. Good luck!

PS if all else fails, get a holy man to do an exorcism...

1986 Wiring

Good work, Steve. I like your idea of scanning and then blowing up the print. My eyes almost don't allow me to read the GM print any more.

I have mentioned it before, but I carry a 30 ft wire with an alligator clip at each end. I use it for providing a direct run from either the battery pos or the battery gnd to any circuit I am having problems with. This eliminates everything in-between. It the wire fixes the problem, then I start checking whatever is in-between.

I have found checking grounds first to be more productive.

Steve,

WOW! You think like I do.... I contemplate and contemplate and enjoy the challenge of figuring it out...

Since I wrote the question...I figured out that the trailer brake actuation light was always on....when it should only be on when you hit the brake. So, temporarily, I disconnected the power supply to the trailer brake actuator (we are trying to get gone on a trip Tuesday.) By disconnecting the power to the actuator, my brake lights operate normally. But, when you hit the brakes the light on the trailer brake actuator still lights up!

For the moment, I have brake lights, running lights and turn indicators so we can get gone. I think I will study the diagram and contemplate it and maybe be able to figure it out....

We'll be back in a couple of weeks....going to Corpus Christi to take the boys to play on the beach...Thanks so much for your work and help. Please keep thinking of anything else it could be...

K&E

Aha! A wild card.. trailer brake actuator has the bug! So much for the brakes... I'm wondering maybe is there also something non-stock about the headlight system?

Because the original GM headlight wiring was so puny, the lights were rather dim when I got my coach. Even before I found the discussion on this site, I put in separate power relays for bright and dim circuits. (great improvement, see info about "headlight relays")

Is it possible someone may have already installed relays in your coach? Depending on how and where the relay coils are triggered, we may have an explanation for strange headlight behavior due to crossfeeding or grounding issues. Just a thought...