New question... Fuse box main 12v White, and White/Red wire

[peng155]

Hi Folks....

New question... When I got the 'Z' the fuse box suffered the usual melted plastic around the fuse holder problem from the high current draw of the lights and accessories through the fuses. I changed out the fuse box with a new MSA replacement about 10 or so yrs ago.

I had to cut the White, and White/Red wires to remove the old fuse box, and I butt spliced the new one in... when I stripped the wires to do the splice I had a look at both of the wires, and did notice that they were pretty well oxidized... I cleaned off the ends as best as I could with some emery cloth, and spliced in the new box.

I also did the one-wire GM internal regulator conversion, I installed a GM/AC Delco SI 10 alternator (I think the 65amp version)

Fast forward to today... while installing the new voltmeter I noticed that the butt splice insulators on the splices to the fuse box had melted, and deformed due to heat.. (I'm going to assume its from the high resistance of the wires due to age)...... I'm thinking of replacing a section of both the White, and White/Red wire from the engine compartment to the fuse box.

Per the FSM... The White/Red wire at the fuse box should be a direct run to one side of the fusible link, thru the link, and to the Alternator output post.

The White wire from the fuse box goes to one side of the Amp meter, and has a splice somewhere to the old external voltage reg. which has since long been removed when I did the conversion to the internal reg. alternator.

Correct me if I am wrong.... I should be able to run a new White/Red wire directly from the fusible link to replace the current one going to the fuse box, And a new White wire from the amp meter to the fuse box to replace the other wire... is this correct?? Or are there other factory tap's, and splices I'm not taking into account??

thanks for the help....

[Zed Head]

Even with a new wire you might still have heat build-up at the connection. It's the resistance at the interface between the two wires, and the interface between the wire and the connector that produces the heat.

Might be more effective to add a couple of relays on the two headlight circuits on the output side of the fuse box. That will remove most of that headlight current from the wires supplying the fuse box. I think it's the reason Dave Irwin's headlight relay kit is so popular for the 240Z's. The running/marker lights pull quite a bit of current also.

[Carl Beck]

Hi Folks....

….snipped.cjb…...

I had to cut the White, and White/Red wires to remove the old fuse box, and I butt spliced the new one in...

Fast forward to today... while installing the new voltmeter

Hi Phil:

Just curious - why couldn't you just unplug the old fusebox from the harness - and plug the new one it? Had someone already modified the factory connectors?

Carl B.

[peng155]

Hey Zed,

I forgot to mention that I already have installed Dave's headlight, and parking light relay upgrade, sorry about that....

Pretty much any high current accessory... driving lights, airhorn, rear window defrost/defog has been has been modified with a relay.

I will say that I didn't do the relay upgrade right away..... so the deformation Of the butt splice insulation, and wire insulation might have occured prior to the relay install. With that being said do you think I need to replace the wires?

Thanks

[peng155]

Hi Carl,

No the wire harness wasn't modified... If I recall correctly... the White, and White/Red wire that was connected to the original fuse box was wired directly to Voltage reg. and to the fuseible link.... I didn't see any connectors for these two wires.... Unless I didn't cut the tape around the wire harness back far enough to expose it

When i did a search last night on my problem I saw a picture of the back side of the box with the two connectors that go to the wire harness, and then the White, and White/red wire...

Found some pictures.... This first one is from a post by Mikes Z car, showing the connectors for the two high current wires..

Unfortunately I didn't have them in my wire harness

this second picture from a post by Blue shows how my looked before i spliced in the new box

The two White wires appeared to be direct runs, with no intermediate connector....

Edited August 24, 2014 by peng155

[Zed Head]

I know that when I was having a problem with my headlight switch (280Z) breaking the solder joint for the running lights I could feel the heat buildup by touching the switch area on top of the steering column. It got hot. It takes quite a bit if heat to melt/warp plastic. You might just leave the lights on for a bit and see how hot things are getting. It might be old damage, it only takes one hot moment to warp the plastic.

I ended up installing relays for both the headlights and running lights on my car so the only current running through the switch now is that needed for the relay solenoids. Tiny amps.

[peng155]

Thanks Zed.... I follow your advice and see if maybe the dis-coloration, and melting is old damage caused prior to me installing the relays.... I also had Dave rebuild both my turn, and head light stock....

Something i just thought of..... with the relay upgrade in place... would I, and should I see the amp meter indicate high current (needle points to the + side of the meter) flow with the head light on?