I am looking to replace a fuel gauge and need to know the Ohm range of the fuel sender.....

Hey Chap -
I've have two senders you can compare to and a Test box that I made to check the gauge. Give me a call and or drop by this weekend and we can check it out.

Paul

Paul, I have plenty of senders around here, I am looking to purchase an aftermarket fuel gauge. I have a full plate for weekend honey doooo projects, my other option is to do the three gauge converson and use the stock sender the other would be easier and less expensive.

Ya got an ohm meter? Hold the sender up-right and take the reading (Empty value) Turn it up-side down take a reading (Full value)

If not I can make the readings tonight.

I will see if I can figure it out with my meter, I will get back to you

Chap-
I dug out my two senders and measured them.
#1
2 ohms full, 71 ohms empty

#2
1.5 ohms full, 76 ohms empty

I checked the range on a gauge and 0 ohms was full and 70 ohms was empty.

Hope this helps.

Paul

"Helps" U DA MAN thanks thats alls I needs..........

0-90!!!!!!!!!

George, is Da New Man....I think.....

George,
was 90 ohms for the sender or the gauge? My gauge was right at E with a 70 ohm resistance, 80 ohms brought it down well below empty and 90 ohms darn near pegs it at the bottom. I assume there is some variability in senders and gauges. Do you see this kind of variation?

Maybe the sender uses the reserve empty at 90?
Im back to confused. Plus I cant find any gauges that are O full 90 Empty there always the opposite of that...... Maybe the 3 combo gauge option is the best option for me.

You could get one of these. . . . Works with the stock sender and has the reserve light!

That appears to be a 60MM gauge not a 2-1/6th, I have been looking for 2-5/8s gauge to replace all of my console guages. Were did you find it.

I remember buying mine years ago at Auto Atlanta, and it is the stock VDO size that fits in their rubber retainers. I used it along with a voltage guage and placed the two in the space where my ashtay fit. Very visable and looks quite original. I think that you might have a hard time finding the guages that fit the stock console unless you find some adapters. You could also just cut a new faceplate for the console with any size and number of guages that you want. It always seemed to me that the center console guages are too far down from the road for any important information while driving, but I'm just getting old and cranky.

I purchase a VDO 2-5/8" gauge this week it fits the console holes perfect without the rubber rings but they dont have a fuel gauge in that size I am now looking at the Auto meter gauges.

That after market vdo gauge 0-90 works perfectly with the original sender (the one pictured in this thread, but actually I never thought about if empty is 90 or 0 ohms! Some of the first small after market vdo gauges we purchased read wrong starting at above empty and going to just before full so obviously backwards with a different ohm range!
Bottom line is that 0-90 aftermarket vdo works great for custom applications.

It is a 60mm can. Not for everyone, however, because of the cost.

I came across four Saab fuel gauges from the early '60s, for five bucks each, and had North Hollywood Speedo (NHS) modify them to resemble the 914/6 GT style fuel gauge. I kept one for myself and sold the others.

If you come across another Saab unit, NHS will modify it for about $150.00. They also make an extremely accurate replica GT fuel gauge that they sell for $250.00. I saw one of those go on ebay for >$400.00.

0 ohms is full, 70-90 or so is empty. The light works on a separate set of electrical contacts on the same float as the gauge sender.

--DD

OK, all you smart guys.

What makes the gauge work one day...then not...lays on empty.
No light coming on.

A couple of trips, then it worked again for a few days.
Now nothing.

I pulled the gauge, its all plugged in.
I pulled the tank....looked a the plug, pulled it an put it back on..all clean and all the wiring seems ok.

How should I diagnose this?
I would like to start at the gauge...
I have three wires, ground and two others.
What am I testing? How am I testing it?

Lemme guess.
Ohm meter between G and ground..that should show me the ohms 0-70 based upon how much gas is in there.
Ground to + would be for the reserve light.

Is that right?
If I get nada on the ohm test...I suspect I will see 0 would that send me off to pull the sender?
Rich

Any electronic guys out here??

Rich

I did some actual measurements on the gas gauge sender. This should settle what the resistance is at various tank levels. The sender I measured is the stock one from a 1970 914-4:

Click to view attachment


Two interesting points are that, if you just insert the typical filler nozzle in the tank and let it fill until it shuts off, you get about two gallons less than full capacity, and filling the tank so full that gas begins to leak out of the overflow still leaves you about a gallon short of the full claimed capacity, at least on my tank.
If you plot this data, it looks like this:


Click to view attachment


What blew me away is the fact that it's so nearly linear, in spite of the very non-linear capacity of the tank vs the fluid height inside, which is what the float actually measures. Apparently, the engineer that did the sender designed a very non-linear resistance element so that the resistance signal is quite linear. I would have expected them to just correct for non-linearities in the gauge or the sender, but not both. I guess we have to remember, this is German engineering.

Which wires are you testing?

Rich

If it's anything like the VW VDO ones, it looks like this. The sensor is a long cylinder with a plate on top with one connection. Inthis view, the cylinder is removed to show the internals

The plate bolts to the top of the tank and has a rod that sticks down. The tank float is a cylinder with a hole in it and bobs up and down on the rod depending on gas level. A tee runs across the bottom to hold the float on. A piece of resistor wire extends down from the plate, across the tee and up to the plate again.

Wipers gently pinch on the resistor wire and mount to the float.

Hook a VOM (or gas gage) to the two ends of the resistor wire and you can measure the resistance from the first end of the wire, across the wiper and up to the second end of the wire. When the float is at the top, the path along the resistor wire/wiper is short and produces a low resistance.

When the float is against the tee (tank empty) the path along the resistor wire and wiper is long, and your resistance will be at a maximum.

Soemthing is intermittent. Check the tank sensor, the wire to the gage, or the gage. A broke wire can cause that intermittent reading.

In my Ghia, it was a broken resistor wire that was captured in the wiper and it would contact (sometimes) on the metal cylinder and complete the circuit. I took the sensor apart, swapped out the resistor wire (found some in the physics lab) added a resistor to tune it, and was good to go.

Wow...
OK, let me try to ask this as simple as possible.

Take off the plug from the sender.
Take and ohm meter.
Touch which two prongs?

OR
From the gauge end.
Pull the wire off the gauge...there are three.
Which ones do you hook an ohm meter to?

Rich

Rich, sorry that we've been answering different questions that the one you asked.

At the sender, there should be three wires, brown (goes to ground), green (to the resistance element), and black (a contact in the sender connects this to the brown wire when the level drops below 1.6 gallons). If you measure at the sender, pull off the plug and measure from the pin on the sender that contacted the green wire to the pin that contacted the brown wire.

At the gauge, the three wires should be green (other end of the same green wire, connects to the gauge), black (same for black, connects to the warning light), and red/white (power to the instrument from fuse #8). If you measure at the gauge, measure from the green wire to ground (but disconnect it from the gauge before you do so you don't read the internal resistance of the gauge).

In either, case you should read the resistance of the sender (0-70 ohms).

Hope this helps.