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Mysterious Burnt Out Wires Under Dash.


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#1 gav240z

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Posted 26 December 2016 - 03:55 PM

So I've noticed this problem on both my 72 240z and #150 (1970) 240z. The wires are a relatively thick gauge white with red stripe.

Does anyone know what they are for and why they might burn out?

The wires are in the driver foot well in the loom near the foot well air vent / tube. (Refer pics).

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#2 WA240Z

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Posted 26 December 2016 - 05:16 PM

Hi Gav, 

 

White with red trace is the main supply from the alternator, so basically powers everything other than the starter motor, hence carries all the current. The melted insulation is just a clear sign of over current load, most likely from a bad connection. If the insulation is only melted either side of the plug in the photo but is fine a 100mm or so after the connector then I would say its just a poor connection in the connector causing the high current. Just cut the connector out and solder in cable to replace the connector. The other problem could be a bad connection else where causing a voltage drop in that wire, once again elevating the current and the plug is the weak link. The cause to all this is two things, one its a 45 year old wiring loam that has had every man and his dog have a go at electrical work on it, the second its a 45 year old wiring loam.

 

Hope this helps mate.

 

Billy.



#3 GongZ

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Posted 26 December 2016 - 06:05 PM

They are the wires going to and from the ammeter. One should be all white and the other white with a red stripe.

 

And as WA240Z said it " is the main supply from the alternator, so basically powers everything other than the starter motor, hence carries all the current." so that the ammeter can monitor the charge/discharge rate.


Edited by GongZ, 26 December 2016 - 06:09 PM.


#4 Gareth. J.

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Posted 26 December 2016 - 06:07 PM

I had this too Gav. It's just like billy says, you'll find the plastic connector has melted internally onto the spade connection which increases the resistance and current draw. It just keeps getting worse over time.

 

I started checking the loom after seeing big fluctuations on the volt gauge while driving. 






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