Courtesy light woes

hey howieb4,
i don't have the schematics with me but for the 72-74gtv (115) the courtesy lights are a three way switch.
With the little lever In the middle the light never goes on.
With the little lever up (?or down) the light will go on (this is the circuit to ground at the light)
With the little lever down (?or up) the light will go on when the door is opened (this circuit the current flows thru bulb, light switch and thru door switch.

I would try removing both passenger and driver's side bulbs. If fuse blows there is a short before one of these two points (most likely).
If no short, try a bulb in one side only to determine if passenger or driver's side is causing the short. (i would suspect the short to be before bulb as if it was after the fuse probably would not be blowing as this is the normal circuit to ground).

I will also check when i get home to see what other components are utilizing the same fuse.

Best of Luck,
Joe

Howie,
the little switch i was refering to is part of the overhead interior courtesy lights.
this is true for both my 73 and 74 gtv's (don't have a 72 yet
i did find here at work a schematic for my 73.
3 fused lines coming off the #1 fuse are rear defroster (big black wire), key reminder buzzer and courtesy lights(red & black wires).
Your neighbor is correct if your wiring setup is as i described above, else logic would dictate that the current goes from the #1 fuse, through the (normally open ie switch/current path closes when door is open, switch is open when door is closed) door switch and upto and thru the lightbulb to ground.
Tracing this short is a little difficult as i believe you have to get under the carpet, headliner, side panels etc. to check the wires.
Most shorts are typically at connections or where a wire is subjected to repeated movements.
Also, and again this is from a 73 diagram, the hot red/black lead from #1 fuse goes first to driver's side cortesy light bulb, and from same side of bulb jumps over to passenger side bulb. (For both sides) the current can then go thru the bulb and to 1 of 3 places depending upon the position of the little arm/switch on the light itself:
1). to ground - light is always on;
2). to door switch (this would be the second wire your neighbor mentioned, it should be solid black) which when door is opened, switch is closed and current can flow to ground
3). No where as the little switch on the courtesy light creates an 'open' position. (lights will not come on when doors are opened)

At least i believe that is the way mine behave.

I will check to see if the 72 schematics and interior lights are different when I get home.

Anyone else care to pipe in here? Feel free to correct me.

Does your car have any other wires coming off the #1 fuse (same side of fuse as your courtesy light wires, not the other side)?
This is important to know to make sure some other circuit (defroster, key reminder...) is not the guilty culprit.

Joe

Jim,
thanks for finding the other thread. it sound like howieb4 might just have some lights from a gtjunior if they are only single wire. if this is the case i'd guess circuit runs from fuse 1 to door jamb switch, to and thru bulb, and ultimately to ground.
Jeff,
excellent point as this would cause a 'dead short' to ground right at the light.

Howieb4 (and any others who may one day stumble accross this thread) ,
as you mentioned your not the worlds greatest with electronics (me either)
just a quick note: make sure the battery Negative terminal is disconnected before you start poking arround the fuse box. my diagrams show the unfused side of 1, 2, 3, & 4 all being HOT to the battery. An accidental touch of that side to any piece of bare metal will definetely not be fun.
Also, in my last post i said it may be hard to find the short...
what i should have said is it may be hard to fix the short... for the previously mentioned reasons.
If you can safely disconnect the three leads (circuits) coming off the fused side of the 1 fuse, battery cable negative side disconnected, you can reconnect just one of the wires at a time to absolutely determine if the interior courtesy lights are causing the short.
And as JeffM recommended you could also try disconnected the wires at the lights themselves to see if the short is actually at one of the two.
With all three of your wires disconnected, and a cheapo volt meter (harbor freight $4.00) you could alternatively check the three wires independently to see if any of the circuits show a short to ground. If your neighbor hasn't left the state , he should be able to show you how to do this in about 1 minute.
Worst case scenario at this point you would have 2 of the 3 circuits you mentioned working just by reconnecting the wires back to fused side of fuse block.
With same voltmeter you can check 'continuity' to findout between which points the short is located.
Then its just a matter of how difficult or easy it is to replace / by pass the bad wire section. (or if you're really lucky JeffM was correct).

Let us know how you make out

Joe

The plot thickens...
Sounds like if you get really lucky JeffM's advice might just work.

Have you unscrewed the lights to see if there is an extra set of connectors up there?

If there are, I would guess these lights would only work if the po had properly rewired the circuit to go through the dood jamb switch first, in which case i doubt you would be having the problem you have now. Or if there was some way they were wired in with another switch somewhere to control on/off.

If there are two connectors at each light, as originally wired, the simplest fix is probably to get the correct lights in place. And with a little quick testing you should be able to determine if the circuit is functioning properly, before you actually buy the lights.

Take JeffM's advice, disconnect the wires at both lights, don't let them touch any metal, and see if a new fuse blows as soon as you put it in.
You should also see at this point if you have two connectors or one at each light.

Jim, if i had perfect memory (not even close), maybe i could have remembered how my old berlina's lights worked - excellent detective work by the way - but back then i was really only concerned with how fast it went, how well it cornered and how easy it was to blow away the bmw 2002's

Howieb4, waiting for the next chapter.

Joe