Gas gauge sender for triumph

[mikem]

My musical friend has a Triumph TR-3 with a bad sender for the gas gauge. It is wirewound on a form about 1/2" diameter and about 2" long and enclosed in a brass can. A cork float is attached to the arm which moves the wiper up and down the wirewound coil. Does anyone have any idea what type of wire is used? What resistance would that coil have? Maybe we could use a wirewound potentiometer with about four times the resistance and use about 1/4 of a turn from the arm and float. They still make these and I would just go buy one if it were mine but my friend is a musician(translation=has more time than money) and I don't mind the challenge. Thanks--Mike.

[darryl]

I've seen those senders being used as a variable resistor in series with the gauge, in other words, a two wire device. If that's the case with yours, you'll need to closely match the resistance so the indication is nearly correct. If it's used as a potentiometer, which will need three wires, it's less critical, but still should be close. If you can post a bit of a schematic of the fuel sensor wiring, that should help to clarify what you might be able to replace it with.

[jfsmith]

What ever happen to carrying a stick that has graduations on it, indicating the level of the tank? May be crude but some people still do these things. I think the gas delivery folk still have to measure the tanker level with a stick.


Jerry

[CCWKen]

Jerry, you're showing your age. My Model T has a "stick" as you describe.

Mike - Nickel Chrome (Nichrome) wire is usually used in those senders. I don't have the specs on the sender resistance but it could range from 30-90+ ohms. If you could find that out, all you do is buy the wire (Probably 30ga.) and use a length that matches the resistance. By the way, that stuf is NOT cheap in small quantities.

You could get a 100 ohm wire wound pot* and use that to determine the E/F sweep. Then just measure the ohms of the pot.

* www.allelectronics.com has these for $1.00.

[ralphe]

Perhaps the fuel tank (sending) unit is similiar to the one in my 1961 MKII Jaguar sedan. I had need of improving its result some years ago and disassembled, cleaned and reassembled it. Since then, it has worked perfectly. I did take some measurements actoss the slide wire at that time and found that it tested at 200 ohms with the tank empty and 14 ohms with the tank full. This is to say the float is down or up respectively.
So, what is really the issue with the Triumph gage? Just repair it and it should work well.

[wierdscience]

If you have the old one,then why not clean it and make sure the contacts are making and see if it works?

[mikem]

The old sender is beyond help. The windings are broken and sagging away from the form. The wire is very thin and would be hard to work with. The arm has a lot of slop in it so the wiper doesn't stay on the coil as it arcs up and down. I may be able to bush the arm pivot to take up the wear but I need to figure out what the wire is to rewind the form. The wire looks copper-colored but someone suggested nichrome wire which is silver. More experiments are in order.

[jcc3inc]

Dear Sir:
Take an ohmmeter and measure the resistance of the remaining portion of the resistor. Then estimate what the total resistance of the unit should be based on the percentage you have measured. Use a mike to get the wire diameter. You should be able to reproduce the original unit with a bit of effort!
Regards,
Jack C.

[Evan]

Why not just modify the sender so that it gives an empty indication when the tank is down to about 1/3 full. Much easier to do than trying to rewind the sensor. Just experiment with a couple of resistors to make a divider that make the guage read full until it reaches the 1/3 level at which time it drops to empty. That is all I had on my Morris Minor, no gas guage, just a light, and it was good enough.

[AZSORT]

Had to do some research awhile back on fuel gauge senders for an additive dispenser project and found that most senders and almost all old ones are 250 ohms full scale. However full scale can either be empty or full. There are not that many variations out there and if you do a web search, you can easily find a few companys that have replacements.