The Stovebolt Site Forums The Shop Area The Electrical Bay adapting sender ohmage

Howdy;
quick question:I'm trying to adapt my '59 fuel guage to read with a later model GM sender.I have heard that a resistor can be added to the sender wire.Anyone know what resistor to use?TIA

First of all, you didn't state the value of the sender. I believe it is 0-90 ohms, but not sure. You can indeed pad the sender with a resistor in parallel but it will be nonlinear, meaning it may be correct are zero but only read 3/4 when tank is full.

From what I have read,all of the later gm senders are 0-90 ohm while the older gage is 0-30.I was hoping to be able to add a resistor in series on the sender wire.If that isn't possible,I will probably replace the gage rather than drop the tank.Thanks for any info.

you're working the wrong way round to add resistance, if it was a 90 ohm gauge and a 30 ohm sender you might make it work, but the 90 ohm sender won't work with an original [30 ohm] gauge, one or the other has to be changed

There is a ton of information on this problem if you do a search. Get a 0-100 ohm variable resistor, remove the sender wire from the gauge post, hook the variable res. to the gauge sender post and ground other side of resistor to gauge case. Turn key switch on, turn variable resistor until gauge reads empty. Turn key off, remove resistor and use ohmmeter to read its value. That ohm value is what your gauge wants to see for an m/t tank. Repeat above test for full tank, 1/2, 3/4, or whatever. For a 0-30 ohm gauge and a 0-90 ohm sender and do the math, you will find that putting a 47 ohm (a standard resistance value)in parallel with 90 ohms (full tank) will give a 30 ohm value to the gauge...great right. But then, when you reach 1/2 tank and the value to the gauge should be 15 ohms it instead will be 22 ohms which looks more like 3/4 tanks. WOW...I'm getting great gas milage with this new sender. Empty will be right on because of the zero resistance thingie, but when you get to 1/8 of a tank and start looking for a gas station, it had better be right up ahead. All-in-all its how you look at things. If you play horseshoes or throw hand grenades, then anything close counts. If you are a sniper...well, you understand. Good luck

You can buy universal senders that should work with to much trouble.
http://www.yogisinc.com/Detail.cfm/-/Product_CD=TAN-GME/Category=376/product.htm

Joe

thanks for the info guys.I did try searching the forums before posting,but couldn't find the specific info.looks like it's not as straight forward as I thought,I may just install an aftermarket gage with a 90 ohm value.