Testing the fuel guage help?

[randy]

Hey, everybody. I've got a 79F. I'm asking for a way to test the fuel guage out of the bike. Has anyone done this, if so please respond. I've got a white, a green and a black coming form the guage and no matter what configuration I use, I can't get the needle to deflect with 12V applied. I do get the tach to deflect, though. I've got three seperate guages and I'm trying to identify a working one to install. I can't believe all three are NG, but I guess it's possible. Any ideas? Thanks in advance.

Randy

[MartyA]

My gas gauge reads full when I top it off, 40 miles later it reads empty. My Clymers tells how to make it work, I think it is too much trouble. I just refill every 100-125 miles and ignore the gauge.

[skids]

There are two problems that can occur (among others) with the standard's fuel gage system.

One, is when the bi-metalic element snaps. This thing is wrapped with wire that heats the element, making the needle deflect. The more current, the more it deflects.

The other, is when you get dead spots on the sender unit in the tank. The float makes a tang move along a variable reisitor, which is a wire winding. Blane Hoops (I think) claimed that you could bend the tang a little so that it make better contact averywhere it is supposed to touch the windings.

The proceedure for testing the float in in Clymers, but it may not test a dead spot in the middle. The output voltage to the sender unit is 7 volts, not 12 volts!

[Bud Manley]

take a 9 volt and apply it to the gauge itself. With 9 volts it takes a little while but the gauge should go up to full.
My problem is the little black box inside the tach that converts the 12 volt signal into a useable 7-3 volt output. I was getting .12 volts from the output with 12 volts applied and a decent resistance from the float valve.
Another link you might want to read

[skids]

Oh yeah... There is a volt regulator in there. I forgot about that! I replaced one of mine with an integrated circuit type for about $5.00. I figured that a 7.5 volt regulator was close enough, but I was wrong. It always read high after that.

Originally posted by Bud Manley
take a 9 volt and apply it to the gauge itself. With 9 volts it takes a little while but the gauge should go up to full.
My problem is the little black box inside the tach that converts the 12 volt signal into a useable 7-3 volt output. I was getting .12 volts from the output with 12 volts applied and a decent resistance from the float valve.
Another link you might want to read

[sixtysix]

Hmmm. I was going to look it up, check the other thread, I already did!

[randy]

Thanks, all for the help. That thread about the hoookups did the trick. Turns out everything works fine.

P>S> Just put the spare (working) Speedo & Tach/Fuel guage on Ebay, if anyone's looking for a set. Item # 2466359609

This is the best web site in the known universe.

Randy