Defy_V8_Miata

So everytime I turn on the head lights my tail fuse blows. It takes out my dash lights and my running tail lights. Ive looked in quite a few places and wraped any wires I could find. I even turned off all the lights in my garage and looked for a spark. I cant figure it out. Any ideas?

charchri4

Hey finally a question I can help with! I have 6 miserable years experience in a Chevy dealer as an electrical systems specialist. What you have here is for sure PITA but it can be handled with a little patience.

The first 2 places I would start are the least likely but easiest to check and often over looked. I would pull the plug on the head light switch under the steering column and with an ohm meter check the switch for shorts. It's very unlikely the problem but very easy to test and rule out.

From there you need a mainstay that I keep in my bag of tricks. It is a 20 amp breaker and a tail light socket and bulb.
http://m.napaonline.com/Tablet/parts...106_0361103357

What you do is take a couple of alligator clips and wire up the breaker in place of the fuse you are blowing. The breaker will heat up pretty quickly and open then it will cool down and close again for half a second. You can hear the breaker snap open and closed but I wire the tail light into this circuit and hang it over the mirror so I can see it flashing too. Optional but handy.

With your clicking breaker and flashing light you have time to find your short with out blowing piles of fuses. So now you can go after the 2nd easy check and that is to pull all the bulbs from the sockets. Yes I have seen a bulb do this if the supports that hold the filament in the bulb are touching. It's not likely but easy to rule out. I probably would not pull the instrument cluster or other dash lights just yet but you may have to get to that point. Anyway if no change with the easy to get to bulbs out then find a connector about half way between the tail lights and the fuse box and unplug it. If your breaker and light stay on now the short is behind the connector but if still blinking keep moving toward the fuse box.

What stinks about this circuit is its big and goes to all corners of the car and in the dash. Just keep pulling connectors till the breaker stops cycling. From there you have narrowed it down and it's basic follow the wire till you find the bad spot.

This process could take 5 minutes or 5 hours so know going in that it is a PITA and allow you self lots of time, lots of beer, good tunes and try to relax and enjoy the challenge.

May the force be with you...

LynnB

What a great idea! Thanks very much for posting this. Has anybody told you today that you rock? If not, let me be the first!

Thanks again,

Lynn B.

Defy_V8_Miata

Well the 20 amp breaker was a good idea but I gave up after testing all of the bulbs and just tracing wire for about an hour. I guess I just will not drive it at night. =D

tbone heller

Start unplugging stuff on that circuit until the fuse stops blowing to track it down.

charchri4

Yeah don't give up. You have a great car and want it done right. It's not hard work just time consuming. Pull bulbs pull plugs and keep going!

charchri4

Hey Defy did you ever fix this? One of the things on my bugs to fix list is no tail lights too!

Defy_V8_Miata

Nope I got the 20 amp breaker and tried for like 2 days... I took out every buld one by one and tested the light in btween each one.. I even took out the dimmer switch as well as the gaudge cluster. I think im just going to put a huge wire in the fuse slot to close it and turn it on and look for smoke.. then fix where ever the fire starts. I dunno tho.

charchri4

Wow bummer. Have you unplugged connectors? Under the dash there is a large blue connector and a large white connector with about 30 pins in each of them. Pull those plugs and you should kill the right front corner of the car and the dash lights.

Just in front of the inside fuse box there is 2 small connectors (maybe 10 pins each) tucked in behind the kick panel. Pull those and you should kill the driver’s side lights.

If still no change just below the inside fuse box is the bundle of wires that goes to the rear of the car alongside the driver’s seat. Find the light wire and cut it.

If no changes from any of that you now have a very small circuit to work with and I'd probably just cut the wire at the base of the steering column and rewire it to the plugs and tail light wire you cut.

charchri4

I got mine working last night and thought about you as I went. I did not know there is a tail light relay under the hood. If you pull that relay you take out quite a bit of the circut and that will help a lot to narrow it down for you. If it still blows with that relay out you are golden because there is not much wire between the relay and the fuse.

Defy_V8_Miata

So I put my car on the lift last night and start looking into this problem again... after just finding random wires and retaping etc. I went to test them and now the tail fuse works fine but the head lights will not pop up by themselves.. I just screwed them up and left them.

charchri4

Hey that is great news! Any change to the situation is progress because you are closer to the source of the problem.

Do your headlights work from the dash button? Mine don't come up once in a while either and I have to prod them with various trys at the button...

Defy_V8_Miata

Yea the head lights turn on just fine... now everthing works.. dash lights.. runnig lights etc. The only thing that changed is the head lights will not pop up by themselves. So i have to go screw them up lol.