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Headlight switch freakout & 30 amp fuse

R

randyf

NAXJA Forum User
Location
Indianapolis
I have a 96 Jeep that I recently changed the headlight switch on. On the plug that goes into the switch, it appears as the current has "jumped" from one wire connector to the other and melted the plastic between. Now the switch is jacked up and won't work unless you kind of pull it out and put it part of the way back in, so I know that is wrong and I need to change it again. My question is how can I fix or replace the plug? It is very tight down there and I had a hard time just changing the switch. The other problem is the 30 amp fuse in the fuse panel under the hood blows and shuts off the ignition. The engine will crank but won't start. I replace the fuse and it blows once you get a few blocks down the street. My first step is going to be checking all of the grounds. I know where 2 are (firewall to valve cover and battery to block), but where is the third? Any help appreciated, sick of riding bike to work...
 
It's the small ground wire from the neg battery cable to the fender wall, but your problem sounds a little more involved. You need to diagnose the circuit for that fuse and find out why it is frying.
 
I just read a bunch of forum posts and it seems like the 30 amp fuse problem may lead to the wiring to the fuel pump or the fuel pump itself.

It is strange, because the fuse will last about a mile before blowing. The first time it happened, I was on the highway and it took forever to find the fuse that was bad. 30 amp under the hood after 1/2 hour of searching for what happened from the pop noise. We drove all the way up north 2.5-3 hours and it never gave me another problem, then a month or 2 later, they hardly last at all. Last time from work I went through 4 fuses...

What do I need for diagnosing the circuit as far as tools?

Thanks
 
As respects the switch/plug, it is unlikely that current jumped from one wire to another -- more likely you have a component controlled by the switch drawing too much current and melting the plastic. This can be a one time event or a recurring one which may apply to you if you have had the switch fail twice.

I changed and rigged mine with a similar problem without removing the lower dash panel but I assume it would be a lot easier to do with the panel removed.
 
Good luck with your fuse... I spent weeks tracing wires and circuits trying track down a short causing a no start, and still ended up taking it to a tech. Basically, you need the wiring schematics from the service manual, you need a volt meter, and a continuity tester is helpful, but you can ohm that out on a volt meter too. Are you getting a CEL?
 
Yes on the CEL. Last night I got under the XJ and found out that the wires going to my o2 sensor are broken and 1 was bare, it looks like they got snagged on something. I unplugged the o2 sensor and drove to work today, no blown fuses on the way in, so hopefully that was the problem. Now I need a new o2 sensor and headlight switch.
 
The plug at the headlight switch is notorious for melting due to the current load. All of it goes through the switch. Lots of us add auxiliary wiring harnesses with relays to move the current load out from under the dash (mostly for hi watt lights.)

Fuzes blowing on the main circuit come from overloads. The O2 wiring could be the culprit. On my '90 - different harness - the fuze blew from excess resistance at the horn connectors. One big honk and it died in traffic. Took a while to figure that one out, and since it was a fusible link, even more to see it.

A '96 is now twelve years old and the wiring harness will continue to develope resistance. If you keep it, plan on cleaning grounds and connectors, replacing cables, etc. A good tool you will need is a volt-ohm meter to read real time voltage, long test leads, and a good idea of how current works in a vehicle. It's not like the house, the whole body is 12 negative for ground - but the cables back from the engine and fenderwell have to still do the last part.

It's obvious when a circuit doesn't work from lack of supply, but bad grounds in Jeeps are a common source for a lot of devious symptoms.
 
On my 97 it's on/off/on/off/on/off/on/off/on... or turn it to the "on" position "5" times really fast.

I've never tried 3 times, but maybe that works, and I am doing it an extra 2 times
 
Well, it's back. I drove it in the rain, got home and the next day drove it about 6 blocks and the fuse blew. Long story short, between my brothers house and mine round trip I blew up 15 fuses trying to get home. It would go for a few blocks and the fuse would blow. So I guess something is getting wet, because when it worked, the car had not been driven in about a week, so whatever is getting wet had time to dry out.

:smsoap: SERENITY NOW!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
Be careful. Repeatedly changing fuses might melt your wiring harness after a while. And be carefull not to use the cheepo fuses. I had one malfunction (not melt correctly) and it fried a wire taking me a month to trace and fix leaning under the dash.
 
I can only speak from experience, but after fighting with wiring for a month last time, I wished I had taken it to the tech sooner. But I do hate mechanics!
 
That is why I am not taking it in. I don't care how long it sits there, I will figure it out eventually. Last time I took a truck in to the local auto electric shop, the invoice said was pretty much "labor - $300", but it was fixed and I never had the problem again. It was an 84 Toyota 4x4.

The thing is, it is just a pain in the ass to find the time to go out there and work on it and track down the problem when you have the wife asking you to do stuff and a kid attached to your leg.

I think I will try and fix it during Sunday nap time. :idea: My only free day...
 
Don't get me wrong, I paid 3 hours of labor at $75 per hour to find a short in the wiring harness, but I tried for a month to find it, and could not. They had the diagnostic tools to run tests through the PCM and a shop with a few different guys working together on it... It would have saved me a month's worth of headaches just to take it there sooner. I am NOT going to run to a shop every time I have a problem, but when it comes to wiring, That was just a big headache I would rather avoid. I did learn a lot, and might be able to more easily solve stuff like that in the future... I hope you find the problem, and it's not too frustrating...
 
You have to find out what is on the 30 amp circuit & then follow those wires untill you find the intermitent short. It's probably going to be a chafed wire somewhere that it moves to make a partial contact which is why it doesn't blow right away.
You can get an aftermarket replacement headlight switch plug with pigtails. You just splice it in in place of the existing plug. I had the switch itself short out internaly which also melted the plug.
Hope this helps.
 
It is the 30 amp fuse that is located in the box on the passenger-side fender. I think it is the only 30 amp fuse in there. There are a few relays and then a series of small fuses of varying amps. The 30 is in the middle of them. I can take a photo when I get home. Thanks!
 
Im not telling you to do this, but i had a lincoln come into the shop a while back with the same type issues. His were in the dash somewhere.
He authorized up a 200 limit on the diagnosis, and then he wanted to be contacted. This car had been to 3 other shops and he was deciding to get rid of it or not.
I ended up wiring a 15 amp circuit breaker into where the fuse was supposed to go that kept blowing. the original fuse was a 30 amp. i did the half rating to ensure that none of the wire harness was damaged while i was trouble shooting the problem. after about 45 minutes, i found a wire that was part of the onboard diagnostic connecter harness was shorted to ground and was blowing the fuse to the ecm.
Also, have you tried to put a new fuse in and did anykinda "wiggle test"? the reason i ask, is instead of driving a few blocks just to stop and replace a fuse, you can try to duplicate the road vibrations one harness at a time.

Now that i think of it, if i had the lincoln issues again, i would prolly wire up a back up alarm to the same circuit, so that way when the tone stopped, i would know that i found the problem. Just a thought i guess
 
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