Possible Dorman 692-102 fuel sender mod

[rogold]

    With a lot of people reverting to using the available Dorman sending unit, I was thinking up a way to fix the resulting inaccurate fuel level displayed.

    According to the Dorman link Fuel Tank Sending Unit | 692-102 | Fuel Sending Unit Without Pump | Dorman Products the resistance of the sender for fuel level is 0-175 ohms (pins C and F on the sender connector) After checking my spare 1989 and 1990 Reatta sending units (well used, of course) I am averaging 25-190 ohms.

     I would think that on the tank wire harness adding a 25 ohm resistor on the pink/black input wire or on the purple output wire would make the fuel level reading much closer when using the Dorman replacement. I guess it could even be added to the internal sender wiring itself, but I dont know if the Dorman unit uses the same color wires as the OEM unit. 

    Anyone else think this would work? If a few others with a good spare sender can confirm my readings, maybe we can come up with a decent fix for this. 

     

 

Edited September 24, 2023 by rogold
correction

[Ronnie]

 

 

On 9/24/2023 at 4:01 AM, rogold said:

I would think that on the tank wire harness adding a 25 ohm resistor on the pink/black input wire or on the purple output wire would make the fuel level reading much closer when using the Dorman replacement. I guess it could even be added to the internal sender wiring itself, but I dont know if the Dorman unit uses the same color wires as the OEM unit. 

    Anyone else think this would work? If a few others with a good spare sender can confirm my readings, maybe we can come up with a decent fix for this. 

I think the question you posted is a good one but I don't have a spare sender. I'm sorry that no one attempted to give you an answer. This use to be the forum to come to for answers to question like yours, but as you can see, everyone seems to have lost interest. Same is true for the AACA forum.  Facebook is the hot place to be for Reattas but that seems to be waning as well. People wanting to sell their Reattas seems to dominate the conversations there lately. 

[2seater]

I think it is a good question as well but I am not sure what to answer. Resistor inline, across the two or something different? If memory serves that sender is for a tank that is not as deep, so the pivot location is too high.  

[DAVES89]

I'm actually happy that the tank shows empty with 3 gallons left. That way should my wife drive the car to empty there is still 3 gallons to protect the pump motor.

[rogold]

     I think if I had the Dorman sender installed, I would put a variable resistor on the input wire from the fuel sender at the BCM. Then start with a empty tank and adjust the resistor until it just shows empty on the gauge. Then start filling the tank to see how many gallons are added before the fuel gauge starts climbing. Then fill the tank to ensure it shows full. Then if the gauge is now working as advertised,  the resistance the variable resistor resistance can be read.  I would probably try a 0-50 ohm potentiometer to start.

    The resistance needed would probably close, but may vary between cars depending on corrosion of the connections, etc.

     I realize this whole procedure should only be attempted by someone with enough automotive or electrical background to be comfortable trying this. And only if the gauge reading off bugs you enough to try it. Most would be happy with the Dorman as it is.

     The day I bought my Reatta the gauge read almost empty, so the first thing I did was drive to the gas station. That's when I found out the tank was almost full and it was the gauge that wasn't working.