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Side Markers/Running/Dash lights out


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Recently purchased '74 260Z with non running side marker lights (everything else lights up). Stock fuse components. PO conveniently cut the wires on all 4 side markers. I spliced one side marker (cleaned housing, etc) and replaced with new same spec bulb. Turned on the combo switch, bulb lit up along with front/rear running lights. Within a minute - all the lights went out. Checked 20A fuse for PARK/TAIL and it's OK (replaced it also, lamps still out), removed fuse box and inspected behind for signs of failure - all looks good too (no crusty stuff). Is my issue now the combo switch like I've been reading?


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good question.. It can be a lot..  Don't know if you are handy with a multimeter but there is a saying here: measuring is knowing, the rest you can forget!  Just follow the power on the wiring.. if there is no power "behind" the switch.. this is the culprit..

It's important to do this in a sertain sequence..  Maybe a circuit diagram (here on the site) of your car comes in handy?  You can learn a lot of this!

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If you have not already done so, download the FSM for your car - it will have your wiring diagram: http://xenonzcar.com/s30/files/FSM/1974 260z FSM.zip

It definitely sounds like you have a dead short somewhere, that is why the PO cut the wires. Interesting that it does not take out a fuse, perhaps wiring somewhere is heating up to the point of separating and killing the circuit. Since everything worked one time when you made repairs and hit the combo switch suggests the switch is not the culprit.

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There is a problem with the 73-76 cars, and the 77-78 cars are only marginally better.

The 20A fuse is too big to protect the wiring, especially with all of the connectors. The weakest connector is the 9-pin connector between the combo switch and dash harness. (The connector is different in the 77-78, but I've seen the problem there, too.) It will overheat with too much current flowing through it. Here is an example of a damaged one that I happen to have handy.


The green wires you see are the ones for the parking light circuit. I hope the damage is obvious. The connection got so hot, the plastic started to melt.

A solution:

  1. Replace the connector. You can find it at http://www.vintageconnections.com/ You may want to buy the pin removal tools. No matter what, it's a PITA to de-pin the old connector IMHO.
  2. Replace the side markers and gauge lights with LEDs. If you replace the front and rear markers, you'll also need to change to electronic turn signal flasher relays. Note: You can't just buy any LED bulbs for the gauge lights. Another user on this site found polarity independent bulbs that fit well. I will attach a suggested list of LED bulbs.
  3. Change the fuse for the parking lights to 10A.

The reason why this solution works is that the current draw through the circuit has been reduced. That reduces the heat through the connector. If there is a short in the circuit, the fuse will blow before there is too much current flowing through the vulnerable connector.


LED bulb list.txt

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Here's a possible approach: if the relay appears to be the only PO mod, consider using your FSM wiring diagram to put everything back to OE state. Then proceed with debugging your wiring from a known baseline. Otherwise you are chasing bugs from an unknown starting position and having to compensate for his mod(s)..

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