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Discussion Starter #1
Hi. I did a quick search for a related topic and only found one thread that talked about a problem almost similar to mine but no real resolution.
I have a 2002 road King Classic and the fuel guage works almost backwards. With a full tank it register dead on E and at about a half a tank tit starts to register tow the full end.. I've had the bike in twice this year for other things and asked that they check that but on both occasions failed to, the only thing they confirmed was that the gauge was operational (by shorting it and confirming it went to full, or something to that effect). My thoughts have been that it may be the sending unit, thinking maybe a connector was reversed because I believe the bike had the fuel pump replaced before I got it and something went back together wrong. I'm told though the connectors only go on one way and that there is a ground wire, send wire and power wire. I question however if it would register at all if the wires were reversed.
Its not a major issue for me since I've always been accustomed to using the odometer for fuel consumption but seeing it always not working properly irks me. I'm contemplating pulling it apart to look at it myself before sending it in to a dealer or elsewhere to fix but to be honest I'm not exactly what I should be looking for when I get it apart. Thoughts?
 

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The sending unit is bad. The float might be able to be adjusted. Find an independent shop that is willing to take the sender out and adjust it. If adjusting won't correct the problem, a new sender is in order.
 

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Hi. I did a quick search for a related topic and only found one thread that talked about a problem almost similar to mine but no real resolution.
I have a 2002 road King Classic and the fuel guage works almost backwards. With a full tank it register dead on E and at about a half a tank tit starts to register tow the full end.. I've had the bike in twice this year for other things and asked that they check that but on both occasions failed to, the only thing they confirmed was that the gauge was operational (by shorting it and confirming it went to full, or something to that effect). My thoughts have been that it may be the sending unit, thinking maybe a connector was reversed because I believe the bike had the fuel pump replaced before I got it and something went back together wrong. I'm told though the connectors only go on one way and that there is a ground wire, send wire and power wire. I question however if it would register at all if the wires were reversed.
Its not a major issue for me since I've always been accustomed to using the odometer for fuel consumption but seeing it always not working properly irks me. I'm contemplating pulling it apart to look at it myself before sending it in to a dealer or elsewhere to fix but to be honest I'm not exactly what I should be looking for when I get it apart. Thoughts?
The sending unit only has 2 wires, no power. Fuel gauge has the 2 wires from sending unit + power.

So it wouldn't matter if the sending unit has the 2 wires reversed.


Looks like youre gonna have to get a service manual. They have the wiring diagrams you're gonna need.


Wonder if previous owner hacked a sending unit for something else to try to get it to work, since the shop troubleshot the gauge and verified that it is working correctly.
 

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Discussion Starter #6 (Edited)
Everyone must be stumped on this one ! So the fuel gauge works , only backwards ?
Correct, consistently, though not in exact inverse proportion

What does the gauge read when empty?
full (or thereabouts, I never let it get quite that low)

The sending unit is bad. The float might be able to be adjusted. Find an independent shop that is willing to take the sender out and adjust it. If adjusting won't correct the problem, a new sender is in order.
That is my fear but I was hoping to be sure before sending it in for replacement. I'm still kicking myself for letting two pass me by on ebay last winter for cheap money.

The sending unit only has 2 wires, no power. Fuel gauge has the 2 wires from sending unit + power.

So it wouldn't matter if the sending unit has the 2 wires reversed.


Looks like youre gonna have to get a service manual. They have the wiring diagrams you're gonna need.
I took it to mean from the manual I have that there were three wires in the connector


this diagram basically shows two



but a photo of the actual unit on ebay shows the three wire connector (and a two)

 

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The black and yellow goes to the sender.

The orange wire is the power that goes to the gauge, not the sender.
 

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Discussion Starter #8
So then when you say it "wouldn't matter if the sending unit has the 2 wires reversed" you're saying it should register properly in either case or that reversed it would not register at all?
 

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Discussion Starter #9
What does the gauge read when empty?
To be honest, now you have me thinking. I only really recollect noticing that it registers dead on E with a full tank and at about half it goes up to full. Later I've noticed it at varying positions between Half and Full but never paid any attention if it was going down linearly from Full as I used up gas below a half a tank. If that is the case could it suggest possibly a bent or incorrectly positioned float arm, something like bobf suggested?

In either case its another variable I'll have to consider. Thanks
 

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The sending unit is simply a potentiometer controlled by the float. It's like a volume knob or light dimmer. The change in position changes the resistance. High resistance when the level is low means less current to the gauge. Lower resistance means more current.

If the wipers in the sending unit are not making contact or have failed, it could result in an open circuit and a dead empty reading. You may have a dead spot in the sending unit at the full position.

The only valid way to know is to remove the sending unit plug and put it on a DMM. Use a hanger wire or whatever you have to vary the float position and read the various resistance readings. Newer bikes are around 10 ohms at full and 70-80 at empty. Older ones are 40 full to about 240 empty.
 

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Discussion Starter #11
The sending unit is simply a potentiometer controlled by the float. It's like a volume knob or light dimmer. The change in position changes the resistance. High resistance when the level is low means less current to the gauge. Lower resistance means more current.

If the wipers in the sending unit are not making contact or have failed, it could result in an open circuit and a dead empty reading. You may have a dead spot in the sending unit at the full position.

The only valid way to know is to remove the sending unit plug and put it on a DMM. Use a hanger wire or whatever you have to vary the float position and read the various resistance readings. Newer bikes are around 10 ohms at full and 70-80 at empty. Older ones are 40 full to about 240 empty.
That sounds logical but if that were the case should it ever read full at all? I would expect in that case (possibly falsely) that it would register correctly for levels where there were no dead spots, but assuming for a moment there are I'm guessing then that it is only repaired by replacing the complete sending unit?

Thanks
 

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That sounds logical but if that were the case should it ever read full at all? I would expect in that case (possibly falsely) that it would register correctly for levels where there were no dead spots, but assuming for a moment there are I'm guessing then that it is only repaired by replacing the complete sending unit?

Thanks
Not necessarily. If the resistive material in the potentiometer has shifted, wrinkled or cracked, it could easily provide a "false" reading at any position. The only way to know anything for certain is to perform the test I mentioned above with a multi-meter.


BTW, how does the low fuel light behave? Is it on when the gauge reads empty?
 

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Discussion Starter #13
BTW, how does the low fuel light behave? Is it on when the gauge reads empty?
Yes, the light seems to operate properly relative to the reading on the guage. At E it is on and stays on until the gauge moves to the other end after about 65-70 miles or so (can't remember the exact distance).
 

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I had a problem with my sending unit.

It would cause the reading to be empty intermittently.
It was the pivot on the float arm that was worn out and causing the potentiometer to loose contact in certain situations.

On my year bike if you get a false full reading, that is symptomatic of a bad gauge.
False empty readings is symptomatic of a bad sending unit.


Again, your service manual will tell you how to troubleshoot your particular bike.
 

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Yes, the light seems to operate properly relative to the reading on the guage. At E it is on and stays on until the gauge moves to the other end after about 65-70 miles or so (can't remember the exact distance).

That is further evidence that it is the sending unit. The low fuel light also uses the signal from the sending unit but it "evaluates" it independently. If it is interpreting the signal in roughly the the same way the gauge is, it seems most likely to be the sending unit.

Again, it is a fairly straightforward test with a digital multi-meter. It shouldn't take more that 10-15 to find out how the sending unit is behaving.
 

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Discussion Starter #16 (Edited)
Again, your service manual will tell you how to troubleshoot your particular bike.
Again, it is a fairly straightforward test with a digital multi-meter. It shouldn't take more that 10-15 to find out how the sending unit is behaving.
Thanks to you both. Am I'm reading this portion of my manual correctly in that I don't have to take the sending unit out of the tank to test it with a meter?





Where roughly under the seat is this connector to be tested?

 

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The connector for the fuel sender would be under the dash panel on the gas tank.

Connector for the fuel gauge is under the fuel tank.
Wires come out under the left side bottom of fuel tank then get routed to the backbone of the frame.


Look in the service manual under the remove and installation section for more info.
 

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Discussion Starter #18 (Edited)
Just a quick update. I didn't get to take the console off to test anything with a multi-meter (would have to borrow one anyway), it was too good a day not to ride. I did however pay closer attention to the gauge after Robert999 asked about the empty reading and it appears to operate properly after it starts registering, albeit incorrectly. At about 70 miles or so (will have to reconfirm that) when it registers full it starts to move down as I burn gas. At just over a 100 (half tank) miles it registered less that full, about 130 it registered three quarters and now at about 154 it registers at just over half. At 177 miles its reading about 1/4 to 1/3. I don't believe I'll let it get much lower before refilling to avoid condensation.

A couple of questions though, I don't see an easy way to accurately assess movement of the float manually to measure with a meter without removing the pod from the tank.
going through the service manual to identify the procedure for my bike to remove the pod I'm guessing that the tank has to be drained, the fuel line depressurized and disconnected to lift it out of the tank (which I assume would be required in any case to replace or even adjust if possible the sending unit)?

Is there enough slack in the fuel line to lift the assembly out with out disconnecting it?



This diagram is similar to mine but the manual doesn't show one for an FLHRCI. The canopy is different on mine and the fuel would be on the right and gauge on the left.

My assembly would look like this



 

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Discussion Starter #19
going through the service manual to identify the procedure for my bike to remove the pod I'm guessing that the tank has to be drained, the fuel line depressurized and disconnected to lift it out of the tank (which I assume would be required in any case to replace or even adjust if possible the sending unit)?

Is there enough slack in the fuel line to lift the assembly out with out disconnecting it?
answering my own question, I found this video on youtube of someone removing the canopy for an electraglide which is similar and there appears to be an ample amount of slack in the fuel line so that it shouldn't require disconnecting. He doesn't mention it but it appears that he must have also pre depressurized the line.

https://www.youtube.com/watch?v=RJvt92Mcx1Y
 

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Discussion Starter #20
I filled the tank again at 185 miles with about a gallon and a half left in it (It took under 3.5 gallons). I don't have any immediate plans to pull it apart this week so didn't want to leave it that long for that long. You can see the gauge before I filled it and when I got it home. I suppose there's no real point pulling it apart without another unit to put in it if needed since after further evaluation it seems to register fairly usable after the first 60-70 miles. Thanks all for your input and for your patience.


 
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