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Parking Light Fuse Meltdown!!!!!


laniadude

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Ok...The problem I am having is the terminal that holds the fuse for my Park/Tail lights keeps getting really hot...It melts the fuse block on the positive side...everything else stays cool The cover says 10A...Thats what I use and it burns..I've went through 3 fuse blocks already...same thing keeps happening...I aslo change the plugs that go into the block... same thing....even the plug is starting to deform from the heat...the green wire on the plug thats for the park/tail light shows no sign of melting or even getting hot...

HELP PLEASE!!!!! I'm already thinking of selling or trading it.....

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You've got something on that circuit that is drawing way too much current; do you have any trailer light wiring? That is the usual culprit on running light issues. I made me a tester from a 25 amp dc panel meter from a piece of equipment, has alligator clips on the wire ends. Pull the fuse and clip the meter on the fuse holders, the circuit will work and it will tell the amp draw. Start unplugging light fixtures one at a time until you get down to about 4 amps, that will point to the problem, did for me at least.

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Unplugging at the connector would isolate that lighting group better than just removing bulbs; it is probably a fault somewhere before the bulb. That's not to say that it might be in the wiring run down the frame, but eliminate the easy stuff first. If your DMM will handle the current, yes, it will work. Most DMM's are only rated for 10A DC, and since you are blowing 10A fuses, they would blow also. I just happened to have a panel meter going spare and put it to use as a test fixture.

 

Say for instance you pull the fuse and take a reading: 17 amps. Unplug the left taillight, 16 amps. Plug that back in and unplug the right one, 4 amps. This would indicate a problem in that group, likely a bare spot that is allowing current to ground somehow.

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Hmmm he didn't say the fuse blew, so we must assume there is normal current flow through the Green/Blue wire to the parking/marker lights.

 

If there is any resistance at the contact point on the positive terminal, it will heat up. Did you use the same old 10amp fuse or a new one? The metal fuse holders are like a copper penny and develop a dull coating on them. If they have been overheated, cleaning them till shiny may not be enough and another fuse block might be needed.

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I thought i did say it blew...lol burn...blew...whichever....I have to work tomorrow so I will check my DMM to see if it can handle it...Now I understand how to test it....Hopefully I find it before the weekend is up...Otherwise I'm gonna start taking pictures for craigslist...Ofcourse I'll post here first!!!lol

Wish me luck!! Thanks guys!!

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The wiring on 620s through '75 was really bad; my Mom's pristine '73 blows a certain fuse the second you install in (the lighter/dome light fuse) and has since 1976. My '74 was cobbled together since the parking light fuse burned clean through the fusebox. Has a FOMOCO circuit breaker there now.

 

I have found that the running light shorts are typically where the wires go through the body between the core support and the wheelwells up front. There's supposed to be a grommet there on each side, usually it has rotted and fallen out, and the wires rub the metal where the grommet was and short out, sometimes intermittent. Miine knocked out the turn signals and hazard fuses within a minute of each other from that. The wires also get pinched under the passenger seat where they go through the floor (those go to the rear) and short out the same way.

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Your battery is not firmly bolted down, is it? Reportedly that causes burnt wiring problems. Me, I didn't use tiedown for 20 years and never had no burnt wiring, but you don't want to risk it.

 

Quote:

Originally Posted by mklotz70

We all have datsuns in common, but only a few of the guys on here actually eat in them, sleep in them, and breathe on them. I love art too, but Datsun comes first. The datos are the canvas for now.....that canvas might change, but the art will continue

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I had the same problem with my 620. When you put a new fuse in and turn the parking lights on do the head light switch and wiper switch light up? That was the problem on my truck, the wire to the fiber optic bulb came unpluged and grounded out the circuit. I don't know if the earlier trucks had the light up switches. The wire is way up there just to worn you. For some reason its on the topside of the temp gauge making it very hard to reach.

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my 620 fuse box did the same thing. i dont remember what fuse it was but it even got hot enough to melt the cover and base. the whole time i had it it never blew a fuse and it had no after market stuff on it.

 

i would think the fusable link would fry if something was grounding?

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The fuseable link(s) are there to protect the wires going to the fuse box in case of catastrophic damage, as in an accident. They should be able to easily carry all the current flow to the fuse box and then some (or what's the point?) All wires after the fuse box are presumably protected by the fuses.

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I was wondering...if it's possible for someone to look at my truck this weekend and help me figure out whats going on with it...my mechanic is gone for the month and I need this electrical problem fixed before Monday...this is my daily driver and I can't afford to miss work...

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  • 2 weeks later...

I dont know if this is fixed for you yet but In my 510 this exact thing happened. I could not figure it out. Finally I went from fusebox to tail lights searching and feeling the wires, turned out the numbnut that owned my dime before me thought a positive and a negative wire went well together and melted all the wires together in that one spot. [which happend to be right underneath my feet on the drivers side]. Just re-wired it and it went back to full operation.

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i am to relaying the headlights with bosch relays so that will not be an issue with the wireing. but i will be looking into the headlight wireing as it will be used as the switch for the relays. unless osmeone else has a better idea.

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  • 6 years later...

In future start your own post so that any answers are yours and not confusing to the person who started this post that you are in.

 

 

 

620 rear lighting wires are as follows for the '77

 

 

Black..................... ground. in one way or another all lighting has to connect to a ground.

 

Green/Blue (stripe)....... side marker, (left and right) license, running or tail lamps. On when parking or headlights on.

 

LightGreen/Black (stripe)... Right turn signal and brake lamp.

 

LightGreen/Red (stripe)..... Left turn signal and brake lamp

 

Red/Black (stripe).......... Reverse lamps.

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