Gauge issues

[Dolfinz]

Now that I have the engine running it's time to address the dashboard electrical issues.  The only gauges that work are the speedo and ammeter.  I figured it might be a wiring issue related to them all so I pulled the dash.  I couldn't find any damaged wiring but notice the terminal block pic attached.  Possible connection issues at this point?  Is there any kind of cleaner or solvent that can be used to clean up the connectors?  Beyond that utilizing the wiring diagram I tried to figure out the concept behind the workings of the gauges.  Can't figure it out.  Black wires to all gauges are clearly ground. Red/blu wires to all gauges appear to be +12 but they are just for the lighting and it appears the resistor/dimmer is in parallel and shunts the voltage but this also doesn't seem right.  Basically I need to verify connectivity from the temperature sensor and oil pressure sensor and the fuel tank sensor to the appropriate gauges but can't verify the wires between the gauges and the sensors.  I have no idea how or where the tach connects so I need some assistance with that as well.  All these gauges worked prior to the engine rebuild so something has changed.  Looking forward to your assistance.

[Dolfinz]

I was looking in the service manual and found wiring diagrams for the gauges on BE-33-36.  That has solved my problem with troubleshooting the gauges.  Still looking for suggestions on the terminal block.  Also need to verify that the in line resistor for the tach is 2.2k ohms.

[SteveJ]

What year Z?

Put the year of your car in the signature.

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On the left hand side of the new screen, you will see Signature.

Click on that and add the year of your car to the signature block. Save it, and in future posts we will know what year car you need help with.

[Zed Head]

Contact cleaner is made for it.  Looks like a 74 260Z so it has the voltage driven tach.  Yes, 2.2 kohm is right.  You should still have the resistor on line, it's black and has two bullet terminals.  Edit - just remembered that the 260Z resistor looks different.  Very primitive looking.  Probably wrapped up in tape.

CRC looks to have a nice one.  Cleaner and protectant.  Hardware stores usually have some, maybe an auto parts store.

Edited January 30, 2022 by Zed Head

[Dolfinz]

1974 is correct.  Thanks for the suggestion on the contact cleaner.

[Dolfinz]

Here's where I'm at.  I pulled the dash to try to solve the problems.  Prior to pulling it the tach, temp, oil pressure and fuel gauges weren't working.  I found the common green wire running to all the gauges feeding them B+ and verified continuity to each so to eliminate the possibility of a faulty connection at the firewall terminal block I separated it out to run directly to known good B+.  I also continuity tested all the sender wires from the senders to the firewall terminal block and verified as good.  Since all the gauges were working prior to the engine rebuild I figured the common B+ wire connection was a likely cause for them all to quit working.  I cleaned all the connectors with the spray and reinstalled the dash.  The tach is now working but the other 3 still aren't.  At this point I'll pull the dash again and I need to test the gauges with the B+ applied to verify their functionality but don't want to burn them up by simply grounding the sender connections as I'm sure the senders have some sort of resistance range.  Can anyone tell me a safe resistance to use to ground these connections to check the gauges?  I will also check the continuity from each gauge to the firewall connectors as I didn't the first time.  Any other suggestions would be appreciated.

[SteveJ]

You could use potentiometers: https://www.amazon.com/TWTADE-Potentiometer-Single-Variable-Aluminum/dp/B07DHGHQPQ

Then you would also see gauge response. Center tap to ground and signal on CW or CCW.

[SteveJ]

Of course, it wouldn't hurt to see if you're getting voltage at the dash to engine harness connector for the water temp and oil pressure and at the dash to body for the fuel gauge.

See page BE-34 for the water temp & oil pressure wiring.

See page BE-35 for the fuel gauge.

[Dolfinz]

Since you're suggesting 100 Ohm pots would a resistor of say 47-50 ohms to ground give me a center dial reading, or at least confirm the gauge is working when a current path is properly provided?

[SteveJ]

You can always just see if you have voltage to ground at the end of the wires in the engine bay and at the fuel tank. No voltage = no signal.

[Dolfinz]

But, does that confirm the gauge is working?  It could be shorted and bypass the voltage without reacting to specified resistance.

[SteveJ]

If it's shorted, no voltage will pass. Since the gauges move on decreased resistance, they would be pegged if there was a short.