Fuel Gauge Help

[mi396ss]

I installed a blazer tank under the box of my 1969 k20 with a new sending unit. I ran a new wire from the fuse panel to sending unit and grounded the sending unit to the frame. The tank is completely empty and the gauge shows 1/4 tank. When I remove the sending unit wire from the fuse panel, the gauge goes to 3:00. When I put a good ground on the fuse panel tab it goes to empty. When I connect the sending wire back up it goes to 1/4 tank. Any body have and suggestions on what’s going on? Thanks
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[1970cstblazer]

Originally Posted by mi396ss

I installed a blazer tank under the box of my 1969 k20 with a new sending unit. I ran a new wire from the fuse panel to sending unit and grounded the sending unit to the frame. The tank is completely empty and the gauge shows 1/4 tank. When I remove the sending unit wire from the fuse panel, the gauge goes to 3:00. When I put a good ground on the fuse panel tab it goes to empty. When I connect the sending wire back up it goes to 1/4 tank. Any body have and suggestions on what’s going on? Thanks
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GM tanks are 0-90 Ohm resistance. When you ground the wire for the tank unit, the gauge should read empty. At 90 ohms, the gauge will read full. Disconnected, that is infinite resistance, so the gauge should max out past full. I would test the tank unit to verify resistance values.

[mi396ss]

Originally Posted by 1970cstblazer

GM tanks are 0-90 Ohm resistance. When you ground the wire for the tank unit, the gauge should read empty. At 90 ohms, the gauge will read full. Disconnected, that is infinite resistance, so the gauge should max out past full. I would test the tank unit to verify resistance values.

So here’s what I found my problem to be. The way that the sending unit is “clocked” to lock into the tank caused it to hit a tank baffle ever so slightly so it won’t go all the way to the bottom. Do I need a different sender?
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[mi396ss]

Originally Posted by mi396ss

So here’s what I found my problem to be. The way that the sending unit is “clocked” to lock into the tank caused it to hit a tank baffle ever so slightly so it won’t go all the way to the bottom. Do I need a different sender?
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I bent the arm enough that it’s reading pretty close to full.
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