josh817 Posted April 28, 2010 Share Posted April 28, 2010 (edited) Hey guys I have a 1972 240z, use to be an automatic tranny Z, for wiring harness reference. Just recently my running lights stopped working. My headlights work, but the running lights do not. I traced it down to the fuse, third from the bottom on the right side of the block, labeled "Park. Tail". I changed the fuse, was good for like a week, they went out again today. So I take out this fuse but its not broken, it has like syrup stuff on the inside it looks like. So I put in a new fuse, every works. I smell that hot plastic smell so I shut it all down and I check, fuse isn't blown, its the right 20A type. Around post for that fuse on the plastic block, its melted. On my fuse cover, you could see it got really hot on one tab, but not the other. The dead fuse from before, shows the same symptoms. Fuse You can't see the melting on the Park. Tail fuse, but its there, only on the side closest to pull tab. It seems like only that fuse prong thing was getting hot, and not the other side. I suspect whats happening is that I'm drawing nearly 20 amps somehow, so it isn't blowing the fuse, but its slowly overheating it. My the only idea I have is that I had one light loose inside the dash. It was a light from a boost gauge so unlike the Datsun lights where it just has a 12v wire and it grounds through the gauge, this one has 12v and a ground wire. The light had pulled loose so the 12v was floating around back there and the ground was still hooked to the light. I would think thats the problem, however if it touched ground, the fuse should blow right away, or **** should begin melting. My other theory is maybe the map light. I noticed that when I moved the vent right above it, you could feel it hitting something and sometimes the map light wouldn't work. Every since this problem, the map light hasn't worked, regardless if the fuse is new or blown. The dome light works, but not the map light, I don't know if the map light uses the same fuse as dash lights... My final theory is the rheostat. It never worked. Maybe its acting up now? What else is hooked to this fuse. I can't think of anything thats wrong because when I put a new fuse in, all my lights work, meaning no stray wires. I'm confused, and worried from the heat. I'd say don't put a fuse in but its my running lights, I need them since that includes the tail lights, for obvious safety. Edited April 28, 2010 by josh817 Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted April 28, 2010 Share Posted April 28, 2010 Our fuse blocks are notorious for corroding, and having loose fuse tabs. You need to check the back of the fuse block, and maybe solder the tabs. Here are a few articles I found: http://www.zparts.com/zptech/articles/fuse_damage/fusedam.htm http://www.zparts.com/zptech/tech_tips/izccposts/izccposts.html Quote Link to comment Share on other sites More sharing options...
josh817 Posted April 29, 2010 Author Share Posted April 29, 2010 Hm ok I will check for corrosion. I think the high heat, over time, is killing my fuses. I put a new one in the day I made the first post. Meaning I used the lights that night, and tonight, so a total of two times, still works. You can definitely tell on the fuse block that the Park. Light tab is melted around it (but still supported) and the "Common" tab which is in the bottom right corner. Today, within 10 seconds of having the lights on, I licked my finger and stuck it on the tab, and it was hot enough to make it sizzle. I was contemplating buying the MSA fuse block but I didn't want to melt that too... Maybe it would fix the problem though. Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted May 3, 2010 Share Posted May 3, 2010 Check this: http://forums.hybridz.org/index.php?/topic/91388-early-fuse-block-on-ebay/ Quote Link to comment Share on other sites More sharing options...
T-Bone028 Posted May 3, 2010 Share Posted May 3, 2010 just a thought...although my fuse box didnt melt like yours (I'm using a painless wiring harness with modern style fuses) I kept blowing my parking light fuse. The culprit was a corroded turn signal bulb and housing/socket. I replaced my turn signal sockets with a pair of generic Ford van 3 wire turn signal sockets that I modified to work (splicing and cutting the plastic to match the oem fit). Just bring one of your old turn signals to your local auto store, and see if you can find something in similar size that matches the same pattern. Over the years, the original sockets get subjected to dirt/vibration/moisture that causes the contacts to get turned around or simply to just get F*$*$ed up. It was causing a short to ground in my scenario. After I replaced them, I havent had a problem since. One way to troubleshoot, is to disconnect as many lights as possible (turn signals, side markers, rears), and then slowly plug them back in one at a time until it blows or in your case, overheats. That will usually tell you where the gremlin is hiding. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 3, 2010 Share Posted May 3, 2010 I posted this the other day at Classic http://www.classiczcars.com/forums/showthread.php?t=38373 Quote Link to comment Share on other sites More sharing options...
josh817 Posted May 3, 2010 Author Share Posted May 3, 2010 I posted this the other day at Classic http://www.classiczcars.com/forums/showthread.php?t=38373 I think I may try that for the time being. Switch over to the new style later on. I don't really want to spend $170 on electrical right now. Quote Link to comment Share on other sites More sharing options...
kce Posted October 30, 2010 Share Posted October 30, 2010 (edited) I'm having the same issue on my '71. The forks that hold the fuse for the tail/moving lights circuit have either got hot enough to melt the plastic of the fuse box due to resistance or the previous owner for some reason hogged out a pretty big hole where the forks and plate are supposed to fit. Regardless, it got hot enough to burn my finger when I stupidly touched the fuse end. I think I'm going to go ahead and check the connections (such as the light bulb sockets) on that circuit and see if I find the source of the extra resistance. It hasn't been enough to burn out the fuse but its certainly been enough to melt the fuse block to where I can't actually get a good connection anymore. Edited October 30, 2010 by kce Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted October 31, 2010 Share Posted October 31, 2010 (edited) Â I just updated this thread for a better "penny pincher" fix! http://www.classiczc...ead.php?t=38373 Edited October 31, 2010 by cygnusx1 Quote Link to comment Share on other sites More sharing options...
kce Posted November 1, 2010 Share Posted November 1, 2010 @cygnusx1: Very clever! Any ideas for what someone in my situation can do for a quick fix? The heat from the forks has melted enough of surrounding plastic on the fuse block to make proper placement of the forks impossible. I've thought about just putting a fusible link in its place so I can get the tail lights working again (currently, I've just used a test jumper to keep me rolling). I have an old fuse block but that I don't want to go all to work to replace the current one just to have the same problem happen again. Should I prep the old fuse block by making sure all the forks and backing plates are clean and then add a little solder to the gap where the meet? Will that eliminate the overheating issues due to corrosion? Or is the only real proper way to fix this issue to upgrade to one of the new MSA fuse boxes? While I was driving today I got a not insignificant amount of smoke coming out from either under the dash or from the steering column area. A quick look at the harness on the steering column didn't show anything amiss but then again, I can't see up underneath the dash completely. I'd say I got some electrical problems! Quote Link to comment Share on other sites More sharing options...
Lazeum Posted November 1, 2010 Share Posted November 1, 2010 (edited)  I was fighting for almost 4 months with some headlight issues. My harness is modified to meet European legislation regarding position & headlight regulations. Regardless of the outcome (it is fixed now!), here the method I believe we should all use when you have a electrical issue on lights. To answer curiosity, the culprit on my side was a loose sidemarker bulb (I had to connect ground from position light to sidemarkers to meet regulations). I changed it and it fixes all my troubles. The bulb was working properly besides the short. My lack of method made me chack every wires possible from the harness, I've dissassemble the whole steering column harness and switches to control everything, etc. So to the method, you should remove all the bulbs from your harness. For the park-lights fuse: sidemarkers, position lights & tail lights. That will open all the circuits. Check your system by turning it on & inspect to see if your trouble is still present (if yes, it means you have a short in your harness system). Then 1 by 1, reinstall the bulbs and check in between each of them if your trouble comes back. As soon as it comes back you can now narrow down your researches. Regarding the fuse box, you can also check the resistance between contacts to inspect for loose connection. Good luck because electrical stuffs are a pain! My topic is it could help: Very Frustrating Electrical Issue with lights Edited November 1, 2010 by Lazeum Quote Link to comment Share on other sites More sharing options...
kce Posted January 18, 2011 Share Posted January 18, 2011 Has anyone used the Headlight Relay Upgrade Harness or the MSA Fuse Box Upgrade? Together they're around $350, which I don't mind spending if it actually resolves the problem, allows me to run brighter higher wattage headlights and are actually quality pieces. Anyone have experience with these upgrades? Quote Link to comment Share on other sites More sharing options...
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