Fuel Tank Sending Unit

Laurence · 03-25-2013, 08:17 PM

Last year I purchased a fuel tank level sending unit (6 volt unit). I didn't install it when I received it. Yesterday, I installed it and it didn't work. Some testing revealed that it is for a positive grounded system. Porsches are negative grounded systems. Via the "Internet", I learned that early VWs to mid-1960s were positive grounded systems. I can't return the unit because I don't have the sales receipt, plus since it's a year since purchase the "Internet" store will not take it back. The store said, "did you use it?" The unit looks just like the sending units for the 6 volt 356 Porsches (the sweep arm with plastic float at end of arm). I have no idea if it can be modified to work in a negative grounded system, which Porsches are.

sixbanger · 03-30-2013, 05:30 PM

What brand and where did you get it. Almost all electiic 12V parts are NEG ground in the US of A.

Les Paul · Les Paul's Garage

My 63 was 6v when I got it. One of the first things I did was 12v conversion. I don't recall having to change anything on the fuel sending unit.

Laurence · 04-24-2013, 02:19 PM

Hello sixbanger. My 1965 Porsche 356SC is a 6 volt, negative ground system. [Porsches at that time were manufactured at 6 volt, negative ground, so my car is old school...the original]

I ordered a fuel tank sending unit for a 1965 Porsche from a vendor, but I think the vendor sent the sending unit for a 6 volt, positive ground vehicle, which VWs back then were 6 volt positive ground (I think).

The sending unit in the 1965 Porsche tank looks like this unit:

VDO Fuel Tank Sending Unit : Amazon.com : Automotive

The unit sold on Amazon is for for VWs. They look exactly alike, but ground is diffrerent.

sixbanger · 04-24-2013, 03:03 PM

All VW's and Porsche's Are Negative ground. Send me a picture of what makes you think it is positive ground so I can see what you are talking about.Or send me a link to the two parts you are looking at/
THX rt

Laurence · 01:14 PM

Sixbanger, thank you for helping me. If my recall is correct, Type 1 VW Beetles were 6 volt, positive ground. The following websites confirm that information:

positive ground battery system??

1964 Volkswagen Beetle

TheSamba.com :: View topic - Positive Ground VW

So, when I ordered a sending unit for a 6 volt Porsche, the vendor sent a 6 volt VW sending unit (VW and Porsche units look the same). The 6 volt Porsche is negative gound. Although I didn't personally diagnose the received unit, my neighbor said the unit received works with positive ground. Since I received the unit a very long time ago I can't send it back (no receipt).

I am not competent to know if the unit received can be changed to function in a negative ground vehicle (the Porsche 6 volt negative ground).

sixbanger · 04-25-2013, 01:27 PM

Yeah, I will send you to the pro's on this. I think you could just reverse the wires and I think it will work.I could be wrong though.Don't want any thing bad to happen to you or the car. SO i will send you th the higher ups. You need to call a guy by the name of Joe Leoni at 1-303 431-5764.Sorry I don't have a e-nail address for him handy but he should be able to help you. Let me know what he says and is it helped you get going. The weather is getting nice.
Good luck.

Laurence · 01:50 PM

Sixbanger, thanks! I have Mr. Leoni's number. I talked to Joseph Leoni yesterday about another issue - about repairing my ignition-starter switch. The number 50 terminal inside the switch is burned out. I didn't ask Joe about the fuel tank sending unit which was sent to me by a vendor (a VDO 90037/8). VDO 90037/8 is for a 6 volt *positive* ground VW Beetle. I'll ask Joseph if I could simply reverse the way the ground and leads are connected. I do not want to screw up my fuel level meter (indicator) at dash. The VDO 90037/8 sending unit is also adaptable for use in World War II-era Dodge Power Wagons, which were also 6 volt, positive ground. See:

VDO fuel sending unit

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