[400GTO]

I picked up a nice 72 GTO a few month's back that had aftermarket gauges for fuel, oil pressure and Temp in the pod next to the speedo. last weekend I replaced the guage pod with a 71 pod I had sitting around out of my old GTO that I had replaced with Rally gauges. I have all the Dummy lights working in the pod but the fuel gauge dosent move. I have tried testing for voltage at the Tan wire in the trunk and got nothing. I tried grounding the wire and no movement, I ran a new fround wire from the sening unit with a new screw attached to the body and get no change. If I ground the actual gauge by running a ground line to the ground lug on the back of the gauge it goes to full.

I tried testing for voltage at the Tan line in the connector near the firewall that connects to the lines running under the carpet to the back and still got no voltage. The aftermarket fuel gauge used the same tan line to mesure fuel level and worked fine.

I have reached my limit of electrical knowledge on this one and really need some suggestions from the electrical Gods on this site!

["QUICK-SILVER"]

You,ve got to be all over it.
You said guage worked when you grounded it.
Make sure sending unit lug is making connection to the printed circuit. Then follow the line on the printed circuit to the plug in the back of the cluster, ground it there and see if it works. Make sure the wire is in the right hole in the plug.
Problem has got to be right there close.

[400GTO]

should there be voltage on the tan wire at either the trunk connector or at the connector just before it goes under the carpet?

["QUICK-SILVER"]

Both places should be the same as the sending unit lug on the back of the guage.

The sending unit, in the tank, grounds the tan wire and makes the guage move.

If you can ground the sending unit lug on the back of the guage and make it go to full, follow the printed circuit to the cluster plug-in and ground it there, guage should go to full.
Move to the plug in that goes under the carpet, ground the tan wire there and guage should go to full.
Same for the trunk plug.

["QUICK-SILVER"]

If you can ground the sending unit lug on the back of the guage and make it go to full, follow the printed circuit to the cluster plug-in and ground it there, guage should go to full.
Move to the plug in that goes under the carpet, ground the tan wire there and guage should go to full.
Same for the trunk plug.[/QUOTE]

NOT
Must of had a flash, should have said empty not full.


Grounding sending unit wire should make guage go to empty, 0 ohms resistance.
Open sending unit wire, no resistance, guage should go past full.
90 ohms resistance on sending unit wire is suppose to make guage read full.

[400GTO]

I replaced the white plastic piece that connects to the two lugs behind the gauge and now the gauge goes to full and pegs there. I guess this is some progress because the gauge wouldnt move at all before. I am only getting .1 volts at the plug in the trunk and the plug going under the carpet at the tan wire. Should there be 12volts on this wire? If I ground the first lug on the gauge (looking at the gauge from behind) it drops to empty.

["QUICK-SILVER"]

The tan wire should be connected to the lug you grounded. The one that made the guage go to empty. Grounding the tan wire should make the guage go to empty.

Testing the way you are; tan wire and sending unit lug, on back of guage, should have same voltage.