Tach, fuel gauge etc go out intermittently

[zdude1967]

OK my tach,fuel gauge,temp and oil preasure as well as the choke light have stopped working a few times in the last couple days. Then they just start working again, wow its the magic Z. In any case this magic is not quite as entertaining as it is a pain in the butt. Any ideas what it could be, the car is a 1974 260z.

Thanks

Glenn

[SteveJ]

Glass fuse going bad, corrosion in connectors, hacked wiring, fusible link, full moon...You don't give us much to go on. When exactly are they going out? Your description is a little confusing, too. Are the gauges malfunctioning, or is it the lights for those gauges? Have you had other electrical issues? Have you checked the voltage of your battery with the car running to see if the alternator & regulator are working properly? Overvoltage conditions can cause issues, too.

[ZCurves]

Not sure if this will help on a 260, but in a 280 there is a cluster of wires and connectors down by the pass floorboard that get corroded and loose. Have look, clean etc.

[zdude1967]

By going out I mean non functioning the tach is at zero and the other gauges are below the zero mark. The choke light does not turn on. It seems to be when the car is started, you start it and then see that the gauges are not working. Then they just come on. The Amp gauge is not affected by this, it continues to work. I had some other electrical issues that you helped me with Steve, that was in June 2011. It was no power to the start switch, I finally found a bad wire in the harness where it comes out of the firewall by the starter. The battery has been a little low lately as I left the interior light on one night. I charged the battery since then but am experencing some fuel /stalling issues and in trying to start the car over and over the battery runs down. I do not believe the stalling / gas issue is related to the gauge issue as if the gauges are working or not it does not seem to have effect on performance, I believe therefore the issues are not connected. In any case I am unsurfe how to check for voltage. If I start the car and pull off the negative battery terminal while it is running if it continues to run does that mean the alternator/regulator works fine.

Your thoughts

Glenn

[LeonV]

The alternator/VR are okay if you measure about 14.5V at 2500rpm or so.

Sounds like a bad connection(s) somewhere. Check continuity at the fuses (not just visual inspection!) in the fuse box first to rule that out. Otherwise, trace wires and clean up connections. I always like to study the wiring diagram before getting to work and reference it while dealing with electrical issues. While slightly more complicated than the 240Z, the 260Z's electrical system is still relatively simple once you've studied it.

[SteveJ]

Glenn,

Thanks for elaborating. It helps a lot. The tach and gauges are on completely separate circuits. As Leon suggested, there could be issues with connectors, quite possibly the dash connectors. If the car is running fine otherwise, it reduces (but doesn't eliminate) the chances of a failing fusible link.

The FSM does break out the circuits in the BE section to make it a little easier than just following the wiring diagram, but you will still need to look at the wiring diagram from time to time. Of course, the troubleshooting section of the FSM does suggest something interesting. A bad voltage regulator could affect your gauges. The EE section tells you how to test the voltage regulator. The FSM is your friend and can give you better advice on fixing your problems than many of us.

[beermanpete]

Glenn,

Thanks for elaborating. It helps a lot. The tach and gauges are on completely separate circuits. As Leon suggested, there could be issues with connectors, quite possibly the dash connectors. If the car is running fine otherwise, it reduces (but doesn't eliminate) the chances of a failing fusible link.

The FSM does break out the circuits in the BE section to make it a little easier than just following the wiring diagram, but you will still need to look at the wiring diagram from time to time. Of course, the troubleshooting section of the FSM does suggest something interesting. A bad voltage regulator could affect your gauges. The EE section tells you how to test the voltage regulator. The FSM is your friend and can give you better advice on fixing your problems than many of us.

The tach requires power and could be on the same circuit as the fuel/oil gauge. The fusible link and voltage regulator are common to the whole car. If these were malfunctioning there would be other issues far more severe than a few dead meters.

Check the fuse that feeds the gauges. Measure it with an ohmmeter. Sometimes they look good but are open. Clean the fuse ends and contacts in the fuse holder.

Using the factory service manual, look for common points in the circuit, both on the positive and ground connections. There could be a bad connection somewhere.