'68 Normal Sporto Combo Gauge Wiring Question

[JT912]

I've been chasing this for awhile now and figured it is time to get some public input. As mentioned, I have a '68 Sporto that had been taken all the way down and is now almost ready to go. The problem is on the combo fuel/oil level gauge. When I turn the key to the first position, the oil level gauge pegs. All other gauges appear to be functioning properly. (Oil pressure might not since I haven't gotten that far). The picture is how it is currently wired which I believe is correct based my my details when tearing it apart. I can't find my sheet to verify though. Things I noted. If I pull off "B" by itself, the needle drops. I can pull the other blue/yellow connections, leaving the "B" intact and it will remain pegged. Also If I remove only the two "A" grounds the needle drops. I've removed both connections at the sender and it still pegs. It seems like I've got something crossed coming from a connecting gauge, but they all match my pictures. Maybe it was buggered up when I got it? Thoughts? Ideas?
Thanks.

[JimVillers]

John .... My guess is that you have a short in your oil level sender wire (green-white). Attached is a part of the wiring diagram that might help, the small combo gauge is #24. Green-white goes to the oil level sender, green-red to the fuel level sender, blue-gold is +12V switched.

Hope that this helps.

[JT912]

I have the same diagram, I am not schooled on reading the many lines that are drawn in connecting the different locations.
Thanks for the input. Seems like a pretty straigh-forward wiring since the green-white goes from the sender to the gauge and then it seems like a ground would be used.

[edmayo]

John, does your combo gauge have both oil temp and oil pressure ? It should if its the sporto gauge. If so then the wiring to the COMBO gauge is blue/ gold (power) to each terminal marked (+) The green/red goes to (G) of oil pressure. The green/black goes to (G) of oil temp brown is ground and goes to the spade on the housing. Blue/black is illumination, and for sporto there should be a green wire to the warning bulb in the temp gauge. If not sporto gauge disregard. Green/white is oil level, but that should be with the fuel level gauge.

[JT912]

It is the oil level gauge I am trying to troubleshoot. I found a much clearer wiring diagram in my workshop manual. It appears things are wired correctly. I am guessing the blue/yellow is a power supply (+) and the brown is clearly a ground. There is a blue/yellow jumper from the pressure combo gauge. I pulled it off thinking it was feeding power to the oil/fuel level combo gauge and the oil level still pegged. I am wondering if the gauge itself my be wonky? I am wondering if I can pull my sender and more directly wire it to the gauge? I wish this were a problem with the pressure combo gauge because there is plenty of internet info on that one.

[edmayo]

The blue/gold is the power wire to all the gauges, and since it is a parallel circuit it sends power to all gauges equally so it doesn't matter if you unplug one or all. You could just have the wires reversed at the level sender, try reversing them. If all is right with the circuit the gauge needle will go full scale in one direction when you pull the power wire from the level sender, and full scale the other way if you ground that wire.

[JT912]

Apparently I have flawed logic. I was thinking that when I unplugged the sender the needle should drop. I was wrong. I had a new sender laying around and hooked it up to find my original sender is bad. I double checked with a multimeter and confirmed that after 45 years and 2 months the old sender has given up the ghost. A little bummed since the new senders are a bit different, but at least I won't need to trace down some random wiring issue. Thanks for the guidance.

[edmayo]

ONLY 45 years,,,,damn,, they just weren't made very well

[JT912]

Wonder if it is still under warranty?

[304065]

Don't throw it away-- the modern sender does not have a stud on the back to allow you to attach the metal cover that is unique to SWB cars. Perhaps you could epoxy on an M6 (I think it is M6, let me check with Ed ) screw on the new sender for an original appearance with modern VDO-ness.