I am trying to use a aftermarket VDO fuel gauge. I am not very clear of how to wire it. Obviously positive goes to switched positive, neg to ground however I wasn’t sure where to connect the sender post on the back of the gauge? I tried hooking it up to the “G” post of the gas tank sender- gauge then reads 0 (even though tank is full). I tried hooking it up to the “WK” post on the gas tank sender and the level goes up to 3/4- even though tank is full. I have used an old gas sender and a brand new one and the same thing happens with both.

Are you sure the VDO gauge is calibrated to the sending unit?

I believe the 914 sender is 0 ohms for full and 70 ohms at empty - or the other way around?

Anyway, some manufacturers have them the other way around and different ranges (e.g. 180 ohms = full, zero = empty).

Hmm not sure if it is calibrated correctly. I’ll try to find out. I am guessing that it probably is cause I get the same readings when I hook the sender up to them a stock gas gauge (multi gauge).

If you take out the sending unit you can imitate an empty tank then check the reaction on your gauge(s). With an ohm meter you can also check the empty/full range to verify the sender is working.

I'm having similar problems with aftermarket fuel gauge in my 944 track car. With that I'm using a VW Beetle gauge where the ohms works in the same direction and added a 10 ohm resistor in line to better line up the ohm range at empty. Not perfect, but close enough for a track car.

Good luck

Most OE fuel senders change impedance. Most aftermarket gauges measure resistance. Or is it the other way around? Regardless, never the twain shall meet.

I do not know what the factory 914 sender or the VDO gauge uses. But I used the following device in my non-914 race car to convert factory (Honda) sender to be able to be read by my resistance-measuring data acquisition system:

http://www.ironcanyonmotorsports.com/icm-fuel-sender/

The 914 gauge reads resistance. I believe it reads low resistance when the tank is full, and high resistance when it is empty. Check the signal from the sender to make sure.

The "G" should be the signal for the gauge, the "WK" is the ground/disconnected that turns on the warning light. The three parallel lines are the ground connection. You do need that hooked up to ground, of course.

--DD

There are two contacts on the sender, one for the actual gauge (reading emptyto full), and the other that triggers the low fuel warning light. I know that VDO makes(made?) two different aftermarket fuel gauges that read 0-90 or 90-0 ohms. I don’t have the info at hand to remember which one was correct, but I’ll try to find my old receipt as I am also using a VDO aftermarket fuel gauge on my 914-6 conversion car.

The green wire should be the gauge and the black wire the warning light (if I’m reading the wiring diagram correctly).

there is a VDO VW-Bug gauge that is a near-perfect match to the 914 sender

i've used it in my -6 for about 15+ yrs

- i posted that info L-O-N-G ago - see message below


.

here is the info from 2004 for correct gauge

"here is the answer via VDO Support:

Use VDO Part Number 301 020 with the OEM 914 fuel sender; (spec'd for Beetle O.E. sender or VDO 221012 sender): 73 - 10 Ohms, "Fuel"

The reading will be off slightly but will not be noticeable

William M. Reichart
Technical Support
Siemens VDO Automotive Corporation
Service & Special Solutions
Phone: 1-800-265-1818 Ext. 4018