blown tail light fuse?

[kais3]

Hello, Last week i attempted to fix the common head light problem by bypassing the junction block and direct wiring the w/b wire with the br/y wire. it worked like a champ. however when i had the car running and turned the lights on it would blow my tail light fuse and the radio, insturment panel lights, and tail lights would go out. since this wasnt happining before i switched everything back problem is still happining. So i have a short to ground problem.

now here lies my problem i have no idea how to read an electrical diagram and have no idea were to start looking for my short. are there any dummy diagrams available? or am i going to have to bit the bullet and finaly take the metro into somebody.

thank you

[Metro Mighty Mouse]

What year? Sedan or hatchback? I may be able to give you a rundown of what to do but I won't be able to start working through it until Fri, probably evening. I have the factory diagram for the 95, should be similar to newer ones as well.

MMM

[kais3]

its a 96 1.0L. i will be gone over the weekend but back at it on sunday or monday. thank you

[danielsatur]

Is there any water, or moisture in the brake lights?
Don't forget to the 3rd brake light.

[Metro Mighty Mouse]

Okay, after a couple hours of staring at the wiring diagrams and looking over previous headlight fix posts I have been unable to locate the brown/yellow wire you connected it to. Where does this wire go? Also, please be very specific about what works and when and when the fuse blows. Right now it sounds like everything works with the car not running and also works with the car running and lights off, but with the car running and the lights turned on the fuse blows. I believe this should shut the car down as well because according to the 95 diagram the ECM pulls power through the tail light fuse. Please check DRL function in all states and be thorough on what does and doesn't work and when. The first thing you might check is light relay 1. It should be in the relay box under the hood. Also look for any melted wires or bare wires especially coming through the firewall. It sounds like the most likely scenario is that when you direct wired it a component or wire got overloaded and cooked enough to short out. You might also try unplugging the headlights and removing all the bulbs and see if the fuse still blows. If not, replace one item at a time until it does and then focus there. This isn't likely to work since the short should be before the bulb (the load) but it is worth a try.

[kais3]

alright the brown and yellow wire is on the back side of the fuse panel on the connector closest to the front driverside tire. it goes into the fuse panel with the headlight realys. http://geometroforum.com/topic/2575236/1/
this forum topic is where i took the information to splice the wires.

i have checked the wires at most of terminals for shorts. nothing.

i am using a volt meter turned to ohms putting the red terminal on the wire and the black on a ground. if the wire is grounded at another location this would close the circut and send a reading to my ohms meter right?

As for what is happining you have it right on the money. the only time the fuse blows is when the car is on and i turn the light switch on. it will kill the radio and inside lights. this still happens with the radio off. the car does not die, my gas milage dropped down to 38 then 41 while driving it with the fuse blown but this could be due to high winds. usually around 45-48 before.

thanks for putting in the time to help me out. this one is testing my every nerve.

[Metro Mighty Mouse]

Okay, finally found the necessary diagram in the factory manual (same items may be in several diagrams and I forgot to look for the DRL breakdown. I was just looking at head and tail lights diagrams). If everything works with the key off, and key ACC, and key on, and the fuse only blows with the car running, the only thing that makes sense (95% sure) is the DRL module has an issue (it has a sensor to tell it when the charging system is active. I am not seeing how it would tie into the tail lamp circuit but it is the only thing I see that should change from not running to running). If it blows when the key is on, car not running, I am somewhat less certain. In the grasping at straws category, try swapping the light relays, one is for tail and the other for head.

You are using the ohm meter correctly. A short to ground would show 0 resistance or an extremely small number. If you are checking a circuit through a bulb you should show a bigger number as you will be measuring the resistance of the filament in the bulb.

The key to your issue is the fact that it works until the car is on (or running). You have to look at what is changing in those states and what in the list of changes could possibly short out the tail lamp circuit. The most likely suspect is the DRL module.

The funny (sad?) thing is, because I was pouring over the DRL diagram, I finally saw the weakness in the wiring layout and the proper solution. It turns out that the headlight relay really doesn't reduce the current through the switch, it is actually wired in after the switch. It appears the most economical place to add relays to the circuits is at the junction block with wires in the same plug as the brown/yellow wire. The red wire is the high beam wire and the red/green wire is the lo beam. You would use a single relay on each wire (2 total) with 12v into the coil (#86 on the relay diagram) and the other end of the coil hooked to the wire going to the plug (#85 on the relay diagram). Then the wire to the headlight connected to the switched side of the relay (#30) and terminal #87 connected to ground. This layout should make the headlights brighter as the path to ground is shorter and will prevent overheating the wiring through the junction block and the headlight switch as they are only carrying enough amps to switch the relay. This also has the advantage of putting the relays out of the elements and away from engine heat (not generally a problem, but failure would be less likely).

[kais3]

Alright I have finally found the problem! of course it is the last thing i would check. there was a wire that was not being used behind the radio that was touching some metal. it must be to lights that would go for the radio since it would only blow when the lights were on.

I will have to put those relays in once i get back from my trip. it sounds easy and it would be nice to have brighter headlights.

thanks a bunch for your help this one was a dog to figure out.

[Metro Mighty Mouse]

Cool, glad you found it!!