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| | | | Joined: Sep 2007 Posts: 24 Apprentice | | Apprentice Joined: Sep 2007 Posts: 24 | 1953, 3100 series, 12 volt. I've installed new sending unit and new gauge. When performing check and I ground the sending unit terminal on the gauge it reads empty but when I un-ground the gauge it only reads 1/2. It's a LMC gauge. I've read on this forum that the gauge itself needs to be grounded. If I ground the shiny area on the back of the gauge the needle goes way past full. Am I doing something wrong? | | | | | Joined: Aug 2005 Posts: 6,377 Ex Hall Monitor | | Ex Hall Monitor Joined: Aug 2005 Posts: 6,377 | I'm not an expert but I don't believe the gauge itself should be grounded. I believe you have a switched wire coming in to the gauge then a wire from the other terminal on the gauge to the sending unit & the sending unit is grounded to the tank by the mounting screws. Are you sure you have matching sending unit & gauge? If you have a 30 ohm sending unit and a 90 ohm gauge you'll never get a correct reading.
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| | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | The gausge itself needs to be grounded to work. It sounds like you have a six volt unit operating on 12 volts. | | | | | Joined: Jul 2004 Posts: 5,708 'Bolter | | 'Bolter Joined: Jul 2004 Posts: 5,708 | bobshollow,
Proper operation of the gauge required it to be grounded. This is usually taken care of by mounting the gauge in the cluster and no additional wire would be required.
Did you buy a gauge that was advertised as being suitable for 12 volts...probably. Troubleshooting the gauge from the connections on its back will work but it won't show any problems with the wire back to the tank.
If you have a ohmmeter, make sure there is continuity between the gauge case and the grounded dash/body.
If there is, I would attach the proper supply wire to the correct terminal, hook up the wire to the tank and do my test from the tank end.
Make sure there is a ground from the sending unit/tank to body.
You have done your homework well. Grounding the sending unit wire should swing the gauge to EMPTY and dangling that same wire in space should result in a FULL reading. It sounds like this actually happens when you somehow ground the case of the new gauge.
Stuart | | | | | Joined: Feb 2006 Posts: 150 Shop Shark | | Shop Shark Joined: Feb 2006 Posts: 150 | I hope this didn't die. I'm interested in the fix and outcome. My 12V gauage reads accurate, however it goes past FULL when the key is off. I don't think my gauage is grounded. My initial install of the new gauage was rather exciting as when the key was turned on, instant cooking of wires. My second attempt included insulating the gauage and the terminals from the dash. So, the question is exactly what and where would the insulators/washers go? | | |
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