fuel gauge wiring

[Guest]

has anyone tried running their own wiring for a fuel gauge? as in, running off an ignition power terminal and running the two sending unit lines up to it? my fuel gauge stopped working. i can't find a fault in it, the sending unit sends approximatly the right resistance, and when i feed power from the battery directly to the gauge, the gauge seems to function fine. the wires test fine for continuity when i test them. i'm not sure what else to check?

[flyingace]

Fuel gauge sending unit relay mod.

[seuadr]

come again?

i'm not trying to sound dense, but i don't understand how a relay would help the fuel gauge?

[Matchless]

seuadr,
The manual on Basscliff's site for the GS850G has quite a bit on page 12-23 onwards that may help you.
Basically if the gauge is OK, it just has to see the negative resistance change from the tank sender unit. I think one wire feeds a ground negative to the sender and the other one feeds the negative variable resistance from the sender unit to the guage. The guage has switched positive already on the other terminal.
If the wires at the tank are reversed the gauge will read empty.
Hope I have it right as this is from recall and my recall seems to fade over shorter periods now.

[seuadr]

seuadr,
The manual on Basscliff's site for the GS850G has quite a bit on page 12-23 onwards that may help you.
Basically if the gauge is OK, it just has to see the negative resistance change from the tank sender unit. I think one wire feeds a ground negative to the sender and the other one feeds the negative variable resistance from the sender unit to the guage. The guage has switched positive already on the other terminal.
If the wires at the tank are reversed the gauge will read empty.
Hope I have it right as this is from recall and my recall seems to fade over shorter periods now.

good to know, but i swapped'em both ways and neither works. i also replaced the bullet connectors with brand new spade connectors, on the off chance it was an issue with a bad plug. if i touch all the connectors together, i get a full tank, problem being, i have less than half a tank. it reads 12v at the headlamp connection and i know that isn't right, because it should have some resistance unless the tank is completly empty. when i tested the sending unit at various places it gave different resistance readings though, per the book. i'm confused. i tried running a wire straight from ground to the sending unit wires, and it shows a full tank then, as well.

[Matchless]

OK, it could also be that the wires and meter are OK, but your sender unit needs proper adjustment. I recall a thread where the sender unit was removed and the littel wiper arm adjusted properly. In actual fact i used it to do mine. My gauge used to show full, then empty then half at times as I rode regardless of the tank level.

[seuadr]

hm. good idea. i'll have to try that out after this tank of gas goes out.. and if i have to put more miles on sooner, well it's for the best, isn't it?

[Matchless]

Maybe, just maybe you have a pinched wire those two wires are easily pinched under the tank if they are not routed properly. Ground going in is black/white and the other one brings out the resistance. maybe my memory is failing me and mine showed full when the wires were reversed, thus putting a full earth on the gauge? Disconnect both and check if there is continuity between the wires from the tank and the frame. If so that faulty earth will override the resistance and then give you a full reading or empty. My bike is in pieces now so I cannot check it unfortunately.
Good luck.

[rustybronco]

Seuadr,
The fuel gauge is nothing more than a glorified ammeter, it measures current flow.
the fuel tank sender is a variable resistor, when the resistance of the sender is high you have low current flow and the gauge registers to one end of the scale, when the resistance low you have high current flow and the gauge registers the other way.
inside the fuel gauge there is a dampening module (slosh module) to keep the fuel gauge needle from moving around with the slightest movement of the fuel in the tank.

you will have a positive wire from the key switch going to a post on the fuel gauge (gray w/ red?), the other terminal of the gauge goes to the sending unit "tank sending unit" (yellow w/ black) and the other post on the sending unit is connected to the frame (black w/ white tracer?).

so the current flow goes from the negative post of the battery (electrons have a negative charge), to the frame through the tank sender, through the fuel gauge and back to positive post of the battery.

http://members.dslextreme.com/users/bikecliff/images/GS1100G_1982_wiring.jpg

yes you brit's have it correct, positive is "earth".

[flyingace]

come again?

i'm not trying to sound dense, but i don't understand how a relay would help the fuel gauge?

Sorry, it was a low-flying attempt at humor.

[J_C]

LOL I thought it was funny.


Shows how much I know about electricity.... flow goes from negative to positive eh.... time to change my perception =]

[seuadr]

Seuadr,
The fuel gauge is nothing more than a glorified ammeter, it measures current flow.
the fuel tank sender is a variable resistor, when the resistance of the sender is high you have low current flow and the gauge registers to one end of the scale, when the resistance low you have high current flow and the gauge registers the other way.
inside the fuel gauge there is a dampening module (slosh module) to keep the fuel gauge needle from moving around with the slightest movement of the fuel in the tank.

you will have a positive wire from the key switch going to a post on the fuel gauge (gray w/ red?), the other terminal of the gauge goes to the sending unit "tank sending unit" (yellow w/ black) and the other post on the sending unit is connected to the frame (black w/ white tracer?).

so the current flow goes from the negative post of the battery (electrons have a negative charge), to the frame through the tank sender, through the fuel gauge and back to positive post of the battery.

http://members.dslextreme.com/users/bikecliff/images/GS1100G_1982_wiring.jpg

yes you brit's have it correct, positive is "earth".

hmm.. i have 4 wires light orange, black with yellow, yellow with black and a solid grey one. now, i ( probably foolishly ) assumed that the grey one was supposed to be grey and red/orange and ran that to the horn positive, the yellow/black black/yellow to the sending unit and the orange one to a bullet connector that was orange in the headlamp. when i disconnect the orange one, nothing happens, however, i think there may be some wiring gremlins, or my sending unit is on the blink. i think this weekend i'll pull the sending unit for testing AND run new wires for the fuel gauge, that way i can be sure of both thanks for the help guys, ironically, although i am going for an HVAC degree i have yet to get good enough at electrics to really feel comfortable with them and not second guess myself :P

[seuadr]

Sorry, it was a low-flying attempt at humor.

no worries, i was comming off work and didn't catch it. i'm all for good modifications, i just couldn't figure out how a relay would improve a gas gauge :P

[rustybronco]

Shows how much I know about electricity.... flow goes from negative to positive eh.... time to change my perception =]

time to read...

http://www.allaboutcircuits.com/vol_1/chpt_1/7.html

[rustybronco]

ironically, although i am going for an HVAC degree i have yet to get good enough at electrics to really feel comfortable with them and not second guess myself :P

Then fix it, don't band aid it!