Bought a new sending unit for my 65 Merc and still not working,getting power from the gauge and ground is good and when the wire from the gauge is grounded it goes to full. Put a meter on the sending unit amd reads 77.4 so is my new sending unit bad.
'Spec' range is 10 Ohms full and 70 ohms empty, but there is a plus/minus range so 77 should be close enough. That would show as empty...
Check it while it's out by grounding it's base. If it's an aftermarket sending unit they don't have that great of reputations...
Remove sending unit from the tank and move the arm thru its range of motion based on the depth of the tank as you check the gauge. Arm might need bending up or down as well as length change. Also, make sure there are no hairline cracks in the float to allow gas to enter.
Besides adjusting the float, make sure the sending unit flange is grounded to the frame and the frame has a good ground to the battery negative to complete the gauge-sender circuit.
Gauge reads empty and its a two prong sending unit and grounds in the trunk and that is good since I can jump the plug and it goes to full.
With the sending unit hooked up and the key on, check the wire at the sending unit that comes from the gauge. It should have a pulsing voltage since you say grounding this wire makes the gauge go to full. With everything still hooked up, check the voltage at the ground prong. If it is zero, the sending unit is bad. If it also has a pulsing voltage, the ground for the sending unit is bad.
It has a pulsing voltage coming from the gauge,its most likely the reproduction sending unit not working or I got the flaot stuck.
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