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fuel sender and damping unit

aapasquale

aapasquale
my fuel level light has been on all the time for a few months--today I removed the fuel pump/level sender from the tank--four wires: brown, green, yellow white (in order)--I'm trying to figure out which is the fuel sender wire--am I correct in assuming brown is ground?--

couple more questions:
--is it okay to turn key to on(not to start position) without the tank/fuel pump/sender unit connected? I want to see if level light on dashboard is on or off when sender is disconnected
--in the wiring schematics there is a damping unit--where is it located on the bike?
--is it possible for this damping unit to fail? if it does, how does this failure present itself?

As you can see, I'm quite new at this, so please forgive my ignorance--
thanks for any help in solving this puzzle
Tony
 
First off, giving us the year and model usually helps; in the title is ideal.

The description you are giving sounds like what I'm seeing in the diagram for my 1995 R1100RS. It looks like the damping unit controls the low fuel light, probably keeping it from flickering, maybe reducing the voltage at the switch in the tank - not sure - just guessing. The brown wire should be ground and the white wire should control the low fuel light from what I'm seeing. I think you are on the right path with turning the key on with the sending unit unplugged, but I'm not sure when the switch should be open or closed with regards to operating the light. If you need some resistance measurements taken, I can pull out my spare sending unit in the next day or two and get them for you. Good Luck - Jonathan
 
my fuel level light has been on all the time for a few months--today I removed the fuel pump/level sender from the tank--four wires: brown, green, yellow white (in order)--I'm trying to figure out which is the fuel sender wire--am I correct in assuming brown is ground?--Brown is Ground

couple more questions:
--is it okay to turn key to on(not to start position) without the tank/fuel pump/sender unit connected? I want to see if level light on dashboard is on or off when sender is disconnected Yes
--in the wiring schematics there is a damping unit--where is it located on the bike? In the fuse box
--is it possible for this damping unit to fail? if it does, how does this failure present itself? Rare I have never seen one fail


Low fuel lamp lights when the float arm drops low enough to close the circuit on one side of the sender board, the damper relay stops nuisance flashing of the light due to sloshing fuel.
Fuel level damping is done internally in the RID display unit.
Level switch is on or off. Brown to White
Sender board resistance range is approx. 2 ohms (full tank) to approx 85 ohms (empty tank) Brown to Yellow
Be sure to carefully clean the sender board with a Qtip soaked in electrical contact cleaner, deposits from fuel will affect fuel gauge readings eventually causing it to read low.
 
mea culpa

First off, giving us the year and model usually helps; in the title is ideal.

The description you are giving sounds like what I'm seeing in the diagram for my 1995 R1100RS. It looks like the damping unit controls the low fuel light, probably keeping it from flickering, maybe reducing the voltage at the switch in the tank - not sure - just guessing. The brown wire should be ground and the white wire should control the low fuel light from what I'm seeing. I think you are on the right path with turning the key on with the sending unit unplugged, but I'm not sure when the switch should be open or closed with regards to operating the light. If you need some resistance measurements taken, I can pull out my spare sending unit in the next day or two and get them for you. Good Luck - Jonathan

Sorry! It is a 1994 BMW R1100RS
Tony
 
my fuel level light has been on all the time for a few months--today I removed the fuel pump/level sender from the tank--four wires: brown, green, yellow white (in order)--I'm trying to figure out which is the fuel sender wire--am I correct in assuming brown is ground?--Brown is Ground

couple more questions:
--is it okay to turn key to on(not to start position) without the tank/fuel pump/sender unit connected? I want to see if level light on dashboard is on or off when sender is disconnected Yes
--in the wiring schematics there is a damping unit--where is it located on the bike? In the fuse box
--is it possible for this damping unit to fail? if it does, how does this failure present itself? Rare I have never seen one fail


Low fuel lamp lights when the float arm drops low enough to close the circuit on one side of the sender board, the damper relay stops nuisance flashing of the light due to sloshing fuel.
Fuel level damping is done internally in the RID display unit.
Level switch is on or off. Brown to White
Sender board resistance range is approx. 2 ohms (full tank) to approx 85 ohms (empty tank) Brown to Yellow
Be sure to carefully clean the sender board with a Qtip soaked in electrical contact cleaner, deposits from fuel will affect fuel gauge readings eventually causing it to read low.

Thanks! My bike doesn't have RID, just the light for low fuel--either on or off-- Have examined the fuel level sender board and it looks very clean
 
checked out sender

my fuel level light has been on all the time for a few months--today I removed the fuel pump/level sender from the tank--four wires: brown, green, yellow white (in order)--I'm trying to figure out which is the fuel sender wire--am I correct in assuming brown is ground?--Brown is Ground

couple more questions:
--is it okay to turn key to on(not to start position) without the tank/fuel pump/sender unit connected? I want to see if level light on dashboard is on or off when sender is disconnected Yes
--in the wiring schematics there is a damping unit--where is it located on the bike? In the fuse box
--is it possible for this damping unit to fail? if it does, how does this failure present itself? Rare I have never seen one fail


Low fuel lamp lights when the float arm drops low enough to close the circuit on one side of the sender board, the damper relay stops nuisance flashing of the light due to sloshing fuel.
Fuel level damping is done internally in the RID display unit.
Level switch is on or off. Brown to White
Sender board resistance range is approx. 2 ohms (full tank) to approx 85 ohms (empty tank) Brown to Yellow
Be sure to carefully clean the sender board with a Qtip soaked in electrical contact cleaner, deposits from fuel will affect fuel gauge readings eventually causing it to read low.

Checked the sender with multimeter--as far as I can tell, rheostat and switch are working properly --I will check the relay for the damper and then check out the wiring to light panel--
 
Be sure to carefully clean the sender board with a Qtip soaked in electrical contact cleaner, deposits from fuel will affect fuel gauge readings eventually causing it to read low.

Wait a sec... this give the impression that the sender board is used for fuel gauge indication but the sender board is only used for the low fuel light. It is one of two components in the tank. The other is the long tube with a float in it that is used for the fuel gauge indication on the RID.
 
Wait a sec... this give the impression that the sender board is used for fuel gauge indication but the sender board is only used for the low fuel light. It is one of two components in the tank. The other is the long tube with a float in it that is used for the fuel gauge indication on the RID.

That isn't the case for all oilheads. The RS does everything from the float arm and sender board. In the case of this 1994, it doesn't have a RID and only runs the low fuel light.
 
That isn't the case for all oilheads. The RS does everything from the float arm and sender board. In the case of this 1994, it doesn't have a RID and only runs the low fuel light.

Does the RS have a fuel gauge of any kind or just a low fuel light? I really don't know.

I do know first hand that for the bikes that do have a fuel gauge display (RID) which the GS and RT do, there is a separate device in the tank for the gauge and the float arm is only for the low fuel light. I was trying to clarify that. Sorry for any confusion there.
 
As far as I can tell, the RS bikes built prior to Novemmber 1993 only had a low fuel light. The ones built after that got the RID as well.
 
update

I have a Damper relay if you happen to need one.:)

Hi all--
found the damper relay in the #2 position in fusebox--when key is turned on, light is on--pull the relay and light goes out--went one step farther and connected the sender unit to bike (not the fuel pump!)--no change to light when arm was up or down--I checked as much of the wiring as I could without taking it all apart--no change--I think the next is to see if I can borrow GSAddict's relay before I purchase another--Is there any way to test this relay?
Tony
 
Have a multimeter or test light and a jumper?

With the relay unplugged, you should NOT have continuity between the terminal (on the relay) where the white / green wire connects and the terminal (on the relay) where the brown wire connects. If you can't see the wires, maybe GSAddict can provide details again. If not, I can pull my spare harness and relay box to figure out what you need to probe.
 
Wait a sec... this give the impression that the sender board is used for fuel gauge indication but the sender board is only used for the low fuel light. It is one of two components in the tank. The other is the long tube with a float in it that is used for the fuel gauge indication on the RID.
RT's are different.
 
do have meter

Have a multimeter or test light and a jumper?

With the relay unplugged, you should NOT have continuity between the terminal (on the relay) where the white / green wire connects and the terminal (on the relay) where the brown wire connects. If you can't see the wires, maybe GSAddict can provide details again. If not, I can pull my spare harness and relay box to figure out what you need to probe.

yes, I do have a multimeter--I will look more closely and see what I can see
Tony
 
hi

my fuel level light has been on all the time for a few months--today I removed the fuel pump/level sender from the tank--four wires: brown, green, yellow white (in order)--I'm trying to figure out which is the fuel sender wire--am I correct in assuming brown is ground?--Brown is Ground

couple more questions:
--is it okay to turn key to on(not to start position) without the tank/fuel pump/sender unit connected? I want to see if level light on dashboard is on or off when sender is disconnected Yes
--in the wiring schematics there is a damping unit--where is it located on the bike? In the fuse box
--is it possible for this damping unit to fail? if it does, how does this failure present itself? Rare I have never seen one fail


Low fuel lamp lights when the float arm drops low enough to close the circuit on one side of the sender board, the damper relay stops nuisance flashing of the light due to sloshing fuel.
Fuel level damping is done internally in the RID display unit.
Level switch is on or off. Brown to White
Sender board resistance range is approx. 2 ohms (full tank) to approx 85 ohms (empty tank) Brown to Yellow
Be sure to carefully clean the sender board with a Qtip soaked in electrical contact cleaner, deposits from fuel will affect fuel gauge readings eventually causing it to read low.

Thanks for the information--one question does remain, however--if this relay does fail, how does this failure present itself?
Tony
 
Thanks for the information--one question does remain, however--if this relay does fail, how does this failure present itself?
Tony
I can only assume (never having seen one fail) that the damping timer would either fail open or closed. Both possibilities are possible.
 
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