Fuel sending unit specs

Buy a potentiometer at Radio Shack or any other electronics shop, or pirate one out of an old radio. Wire one outside leg to ground and the center lead to the wire that feeds the signal to the gauge. Leave the third leg disconnected. It will read either full or empty at zero resistance, and either full or empty at some resistance value(depends on how the gauge is configured). Turn the knob slowly as the pot you find probably has way more resistance than you need. Most senders are less than 200 ohms IIRC. Measure the resistance with an ohmeter and you'll know the sending unit you need.

You can check the gauge by grounding the signal lead, then leaving the signal lead disconnected. You will know if your gauge is still good that way, it should alternate between full and empty.  

danny: you=smrat feller

i'm going to grab one tonight.  i have a full tank, but only show 3/4 on my gauge.

I hate that Radio Shack is becoming less an electronics store and more a cell phone store.

I had to go online to get a resistor I wanted and had to get 50 when I only needed one.

If anyone wants to use an LED for an alternator light I can give you the resister you need to put in parallel.

If you have a VDO sending unit (replacment for original), the most common are either 8-80 ohms or 0- 90 ohms. Check your gauge as suggested above then the sender. If it is an original unit you will need to check the resistance range. Other things to consider if is a newer VDO unit and installed without bending the float lever to obtain a full range of drop in the tank it's not going to read correctly ever.  Another is if it is an orig unit the angle that the tank sits in the CMC is different from that of the VW. My VDO unit had instructions how to shorten the vertical bar that holds the float lever. Then the fun began bending the arm and checking several times to get the most complete up and down motion possible for the float.

This is all best done with an empty tank. Oh and it was also easy as the tank wasn't installed in the car.

Bill M

Mike, digikey.com, mcmelectronics.com, or partsexpress.com. I haven't bought from the Shack in YEARS! No need to buy 50!

Mango, I bent my sender arm to read full at full, but it runs out shortly after 1/4! So maybe leave it alone, as it is more important to know when you're going to run out than how full you are!

Here's what I did-

I gave up. Henry popped apart a tank sender and pulled out most of the windings on the mechanism, but left in the ones that the wiper arm contacts when the float is at the bottom its the stroke. Rather than a variable resistance gauge, the sender is now just a switch.

I had North Hollywood Speedometer take out the fuel gauge on the "combi" gauge, and put an oil pressure gauge in instead. I also sent my tach in to be rescreened and rebuilt with good guts, and had them replace one of the redundant lights with an amber "low fuel" light.

Now, I have a useful instrument in my gauge, I can use the tripometer to know where I am in the tank, and if I should get close to empty, a light will come on in my dash.

It beats the heck out of a useless gauge, which will remain useless no matter how many resisters are put into the circuit (the ohm range of the gauge is just incompatible with the sender).

Forewarned is forearmed.

Danny P and others:

Thank you for the gtreat suggestions on the gas guage problem. I am going to the garage to work on it now and I will let you know if I made any progress. This is the great thing about this forum when i can receive suggestions for fixes that I cannot get anywhere else.

Thank you all!

Renfrance

picke3d up a 1K potentiometer this am.  that was the lowest they had.  cost me $3

i'll wire it in tonight and post back.

well, it didnt go so well for me tonight.  instead of thread-jacking, i started my own.

https://www.speedsterowners.com...g-fuel-sendergauge-q