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Headlight fuse #2 keeps blowing


Ral

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This is a new car for me so I'm seeing the work previous owners have done as I dig into it.  I've been working on the instrument cluster and had the odometer fixed recently.  While I was there I replaced all of the lights on the dash since none of them were working.  Installed the dash and still no dash lights.  Pulled the cluster again and checked the continuity of the circuit board.  Looked like 2 out of 3 lights should have worked so I installed it again to test.  Pulled the headlight switch and for a brief moment I thought they were working.  New problem is that #2 fuse was blown so I thought that was the problem.  Nope, now it's a new problem.  Every time I pull the light switch to the first position I blow #2 fuse.  I disconnected and removed the instrument cluster, same problem.  I then pulled the fuse box and checked the wires hooked up to  the #2 terminal.  There is a single wire and a two wire connected to #2 terminal.  The two wire connector goes to ground when I pull the light switch to the first position (parking brakes?).  Looking at the wiring diagram it appears one of the wires goes to the right front headlight and the other goes to the taillight.  I have been chasing wires all day and have not found any signs of a wire going to ground.  Any helpful hints in chasing a wiring problem would be much appreciated.   Oh ya, 1971 2002 with 12 fuse box.

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Could be the light switch or the rheostat is turned all the way counter clockwise, a disconnected wire or a failed switch.

Fuse 2 blowing means there's a compromised wire or connection creating a short circuit creating heat enough to blow the fuse.

 It's highly recommended to add a grounding wire to the rear two brass knurled nuts on the back of the Multi-Gauge. Use 2 U connectors one for each nut, a disconnect insulated spade joint & another U connector under the dash. I tend to use the heater core stud. The simple ground harness is this.
U___U_________><________________________________U

 Both front Turn Signals are grounded by the two mounting screws.

All other grounds are medium brown wires.
Check the wires at the Alternator both bail wire plug & ground loop (may need to re-crimp ground)

In the Engine Bay, the Yellow Tape Voltage Regulator has a ground at one of the screws.
Tail lights are grounded on the metal housing.
Under the trunk boards on the center rail is another ground.

If your headlights have a small  5 to 7 watt "City Light" at the lower part of the headlights, be sure the push in bulb connector is pushed in fully. If this becomes dislodged it will ground making a short circuit & blow fuses immediately.

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Andrew Wilson
Vern- 1973 2002tii, https://www.bmw2002faq.com/blogs/blog/304-andrew-wilsons-vern-restoration/ 
Veronika- 1968 1600 Cabriolet, Athena- 1973 3.0 CSi,  Rodney- 1988 M5, The M3- 1997 M3,

The Unicorn- 2007 X3, Julia- 2007 Z4 Coupe, Ophelia- 2014 X3, Herman- 1914 KisselKar 4-40

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Thanks for the pointers and advice.  I was also thinking the switch was bad but I took it apart and it seems to be ok.  I'm going to hook the switch back up and pull it to the first notch where I start to experience the ground and probe to see what terminal on the switch is causing the ground and then trace it back.  I see a cluster of brown wires under the dash that are clearly grounds.  I'm going to use this connect for the Multi-gauge as you suggested.  The good news is that I'm learning a lot about the wiring as I pull my hair out on this one.  I feel like Biff on Back to the Future when he says "I hate manure".  Substitute "electrical problems" for manure.   

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Spend some time in this tech article to learn more. One thing I didn't see in your initial post,  are you running original sealed beam headlights or upgraded H4 lights?  

 

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74 tii (many mods)
91 318i M42

07 4Runner

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They look like original sealed beam headlights with 3 prongs coming out the back.  The previous owner did convert the parking, turn signals, and license plate lights to LED.  

 

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One other point I should mention.  The battery has been moved to the trunk with a red lead running forward but the ground is wired to the metal wall behind the back seat.  Thanks for the pointer to the article.  Just starting to read it.

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An old school trick for chasing shorts... get a 12 volt light fixture/socket (or solder wires to a bulb) Wire up a couple leads with alligator clips, a couple feet long so you can place the bulb where you can see it from all angles. Connect one lead to 12 volt positive (alternator in your case) and the other to the out going side of the #2 fuse bracket, no fuse in. With a dead short the light will illuminate. 

Then go about disconnecting and wiggling harnesses, relays, etc until the light goes off. I use a 1156 bulb. Found a screw through a wiring harness by a careless trim installer on a boat recently using this setup. Once it goes out you can begin reconnecting stuff and narrow your focus on the short. Good luck!

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'Once in a while you get shown the light, in the strangest of places if you look at it right'

Robert Hunter, Scarlet Begonias.

 

Gunther March 19, 1974. Hoffman Motors march 22 1974 NYC

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LEDs, there's part, if not all, of the problem. These cars are meant to have incandescents.

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Andrew Wilson
Vern- 1973 2002tii, https://www.bmw2002faq.com/blogs/blog/304-andrew-wilsons-vern-restoration/ 
Veronika- 1968 1600 Cabriolet, Athena- 1973 3.0 CSi,  Rodney- 1988 M5, The M3- 1997 M3,

The Unicorn- 2007 X3, Julia- 2007 Z4 Coupe, Ophelia- 2014 X3, Herman- 1914 KisselKar 4-40

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1 minute ago, Chris_B said:

There is nothing inherent in an 02's electrical system that won't support use of LEDs, except perhaps the flasher used for the turn signals and emergency lights.

The alternator light needs to be a incandescent bulb for the charging system to work.

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If everybody in the room is thinking the same thing, then someone is not thinking.

 

George S Patton 

Planning the Normandy Break out 1944

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Day 3 of chasing wires.  Made progress with the #2 circuit.  Took the light switch apart and cleaned it.  I can now put the switch in the first position and it doesn't ground out #2.  Not sure what I did and even though it's working I have my doubts that was the problem.  New problem surfaced as I was chasing wires.  The red wire from the battery to the ignition switch is somehow grounded.  After hours of removing the tape around the wires I was able to trace the problem back to the fuse box. When I disconnect the red wire going to #7 circuit the grounded ignition wire is no longer grounded. I'm now noticing 4 or 5  circuits in the fuse box as showing a ground.  Nothing in the fuse box should be grounded.  Right?  This was a working car a week ago and now I'm having all kinds of random grounds.  Could a fuse box go bad?  This is a 12 fuse box.  Are all of the circuits on the box isolated?  Seems like I have some serious weirdness going on.  None of the wires on the underside show excessive wear and I don't see any insulation that could be questionable.    Does the box have a circuit board on the back side? Thanks for all the pointers and help.  

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Check the dual ground strap at the battery.  The larger braided strap should go to the engine block, and a smaller one to a ground point on the body.  If the body ground is frayed, broken or not fastened properly to the body, all sorts of odd grounding problems can arise.  Check that negative battery ground strap thoroughly, especially where the braided wire is crimped to the battery terminal, and where the ring terminal on the other end is fastened to the body.  

 

If the body ground strap isn't making good contact, then the car's electrical return path must go through things like the accelerator linkage--a very poor path for those electrons.

 

mike

'69 Nevada sunroof-Wolfgang-bought new
'73 Sahara sunroof-Ludwig-since '78
'91 Brillantrot 318is sunroof-Georg Friederich 
Fiat Topolini (Benito & Luigi), Renault 4CVs (Anatole, Lucky Pierre, Brigette) & Kermit, the Bugeye Sprite

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2 hours ago, Ral said:

The red wire from the battery to the ignition switch is somehow grounded. 

A few notes on wire colors in our cars:

Solid Brown wires are always to ground.

Brown wires with a colored stripe are ground wires controlled by a switch... e.g. Brown/yellow wire connects the horn relay (tab #85) to ground thru the horn button.

Solid Red wires are always HOT and Not Fuse Protected.

Red wires with a colored stripe (usually white or yellow) are always HOT (+12v) but protected by a fuse... e.g. Red/white wire from fuse #8 to the hazard button.

Most wires with a stripe are protected by a fuse, however there are exceptions.

 

Are you sure you are measuring continuity, 12v, etc. from the supply side of the fuse (not the fused side)?

You can detect grounds if the circuit is protecting something such as a headlight that is always grounded (thru the filament) and controlled by voltage to the hot side of the fuse.

The "hot" side is normally the Right side on both 1-6 and 7-12 fuse box terminals.

 

Any solid Red wire shorted to ground would result in a possible fire...it is not protected by a fuse!

The Red wire from the battery (+) goes to a solder connection then branches off into 4 other solid Red wires.

1) Red wire to the alternator B+.

2) Red wire to the horn relay terminal #30.

3) Red wire to the ignition switch terminal #30

4) Red wire to fuses #7 and #8 (these are linked together). Also, a Red wire from the "hot" side of fuse #7 goes to the diagnostic plug pin #1. Easy to check with a voltmeter...should always be +12v.

 

Start with fuses #7 and #8. The fused protected wires are Red/white:  #7 goes to the Lighter.  #8 Red/white wire goes to the Hazard Switch. From the Hazard Switch connection, 3 additional Red/white wires connect to:

!) Instrument Pod pin #2

2) Interior light switch in the cabin

3) A 9-pole connector (under the dash) that supplies the Turn Signal switch and the warning buzzer controlled by a Brown/green wire to the ignition key contact switch (the little 2-pole box next to the ignition tumbler),

 

Sorry for the long response, but I would start by tracing the Red/white wires from fuses #7 & #8. This should reveal what is popping your fuses.

 

John (aka: "Sparkie")

 

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