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914World.com _ 914World Garage _ Fuel sending unit

Posted by: azbill Jan 4 2005, 11:26 AM

Can anyone tell me the full/empty ohm output of the fuel sending unit? I'm thinking about redoing the gauge cluster.

Thanks
Azbill

Posted by: Dave_Darling Jan 4 2005, 12:03 PM

There aren't any official specs that I know of. I have measured mine, and it was "about" 35 ohms empty, and "about" 10 ohms full.

You can measure yours, too. Just unplug the wire to the sender from the gauge, and measure the resistance from there to ground. Or unplug the wire from the sender itself on the top of the gas tank.

--DD

Posted by: lapuwali Jan 4 2005, 12:43 PM

I've gotten similar numbers with my sender (5-33, full to empty, in my case). This is the same, apparently, as the 911 sender, at least for the early cars. You'll find that the only gauges that work with this ohm range are the stock gauges. No one, not even VDO, make a gauge you can still buy new that works. The "standard" VDO ohm range is 10-180. I also note that several people have measured their own senders and gotten very different figures (10-75 is the most common set of figures I've heard). Some have stated that the 10-180 ohm VDO gauge works.

I'd measure yours, as it's possible there's more than one sender available. This seems unlikely, but I can't explain the results otherwise.

Posted by: MXMARK Jan 4 2005, 01:09 PM

Azbill, My 72 was 74 ohm empty and 5 ohm full. If you are looking for the right vdo fuel gauge for these readings let me know. Thanks I hope this helps. Mark

Posted by: trekkor Jan 16 2005, 10:23 AM

This what I need as well.

Help IPB Image

KT

Posted by: MXMARK Jan 17 2005, 12:30 AM

Trekkor what do you need the part number to the vdo fuel gauge ? good job on the 6. I have had a 2L six in my garage for twelve years maybe I will install it. If you need the vdo number I will go get it. Thanks Mark

Posted by: sixnotfour Jan 17 2005, 12:55 AM

QUOTE
Hey Trekkor,

I just picked one up from Harmut at palo alto speed for $60 IRCC. VDO Fuel Gauge for 914 sender (VDO: 301-030-003) 60-90 to .5 Ohm

It's got a potentiometer so you can adjust the range. When I received it the gauge was pre-calibrated for the 914 sender.

-bryan

Didnt this work ? IPB Image

Posted by: 914Timo Jan 17 2005, 02:03 AM

QUOTE
74 ohm empty and 5 ohm full.

According data from VDO it should be between 60 to 90 ohms as empty and about 2 ohms as full.

I have used many years VDO 3309556 fuel gauge with original 914 sender and it works great.

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Posted by: MXMARK Jan 18 2005, 12:57 AM

That looks like the same one I have. The part number that I have is 320 020D or 320 020. This Gauge is adjustable from 60 to 90 ohm for empty so you can adjust or fine tune the empty reading. I picked mine up from my local VW store Car Craft in Riverside, it works great. I hope this Helps Mark

Posted by: Dr Evil Jan 18 2005, 01:31 AM

When I called North Hollywood speedo, and Palo Alto Speedo they told me that we run 10-180 ohm. The wierd readings that you get when mesuring your slef could be from the nature of a rheostat or something. the sender is capacitive, is it not? If it is than you can not just measure the resistance.

I could not find a VDO gauge withthe number 3309556, all of the numbers that I saw foe fuel were like 301-XXX

The one I was told that I needed was 301-015 pictured below.

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Posted by: lapuwali Jan 18 2005, 10:10 AM

We've had this conversation before. The stock sender is not capacitive, and there's nothing in the nature of rheostats that makes them dificult to measure. The stock sender is a pair of high resistance wires with the float sliding on them up and down a tube. The float conducts between the two wires. When the float is at the top, the total wire length is short, so there's low resistance. When the float is at the bottom, the current has to go all the way down one wire, across the float, and back up the other wire, so the resistance is high. Nothing magic about this.

301-015 is 10-180 ohms, according to the catalogs I have. There is a 0-90 ohm gauge, used with GM fuel senders, which would work if the sender is, in fact, about 5 to about 80 ohms. This is, in fact, a very common gauge. The British used it in their later (post about 1966) cars. There is also a 90-0 ohm adjustable gauge, but it's discontinued.

The 330 gauge Timo mentioned might be a Europe only gauge, or a different part numbering scheme.