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My LH fuel sender was acting up. I ordered a replacement from SNG Barratt. It was an aftermarket unit because the OEM one was special order.
This aftermarket unit has three terminals while the original has 2. The aftermarket terminals are distinguishable because one has a black wire leading from with with a male connector. Another terminal was just a plain male connector on the white plastic mounting plate. The other terminal had some kind of cover on in. Like a clear rubbery plastic terminal protector. The unit came without directions or any kind of wiring diagram. I hooked the car's black wire up to the new unit's black wire and the green wire up to the uncovered male connector. Added gas and the damn thing didn't register.
Now I have either miswired it or the long arm is hitting something inside the tank. Does anyone know for sure what terminals go to what on this aftermarket unit. I called SNG Barratt and the person said I could leave a message and someone may call me back in a few days.
Hi, not sure how the new sender is wired but the original ones read approx 18 ohms full to 250 ohms empty. Try measuring between the three terminals on the new one, maybe it has a separate ground connection ? I know when i reinstalled my sender's with new floats, I put the floats on the wrong way making them hang up. Hopefully it's just a wiring issue !
Cheers
Brian
Generally speaking, a gas gauge translates resistance readings to needle position. The guage has specs of what resistance equals empty and what resistance equals a full tank. That's how it's supposed to work. So you need a sending unit that has the correct high and low resistance as the arm swings from full to empty. Don't forget that if the wires from the sender to the guage have bad connections that adds resistance. Finally universal senders are designed to be mounted in different orientations and for different resistance readings. So it's really difficult to get everything working together to produce the correct guage reading.
The way I would approach it is to find out what resistance the guage is looking for at full and empty. Then (hopefully before you install the sender) check it on a bench with a multimeter to see what it's output is. Then you know which way is up and which way is down. At that point you can bend the arm to fool it into giving the right reading at the two extreme positions. You can also wire it up outside of the tank and move the arm and make sure the guage is reacting appropriately.
It's easy for the factory. The designers pick the right components and test them and the factory folks install them correctly. For us 30 or 40 years later it's very tricky to get everything right at the same time and work as intended.
FYI, I just did as Doug suggested. Switching the Green wire to the other (protected by the clear rubbery/plastic terminal protector) resulted in the gauge pegging to empty. Switching it back and the gauge came up. So the arm is hitting something in the tank. The SNG product page indicates that this MAY occur. What is should say is that IT DOES occur and you have to bend the part first. So it is drain the tank, bend the arm and reinstall.
As Mustie1 says :"We do it right because we do it twice!"
To square the circle ( and to make the thread searchable) when you buy the SNG Barratt after market fuel sender unit, the black wire goes to black. the green wire goes to the open terminal (the one without the protective thingy on it) and you MUST properly prebend the arm so that it more or less follows the path the original did. New sender now working,
New Fuel Sender Unit Aggravation
