Author Topic: C10 Fuel Gauge Resistor Mod with Pics, by "ZG1K"  (Read 9708 times)

Offline elvin315

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C10 Fuel Gauge Resistor Mod with Pics, by "ZG1K"
« on: May 23, 2011, 11:17:15 pm »
After putting a little over 3 gallons of gas in my 7 gallon tank due to the gauge reading empty, I read about this on the forum and found the trick is to put either a 220 ohm or variable resistor in the wiring. Since I had a box of resistors and it was a "free" repair, I decided to tackle it using the 220 ohm version. I did this w/o removing the tank.

First, parts & tools needed (what I used, as a general disclaimer, you can do this your own way). Also, this was done on my 2006 C10, so your wires may be of a different color. The principle is the same.

1. Soldering gun & rosin core (electrical) solder
2. 220 ohm resistor (1/4 watt is fine, Radio Shack PN 271-1313, if you have a box of resistors like I do, it is the one with the red-red-brown-gold bands on it) Click here to decode a resistor.
3. Small (jewelers) screwdriver or cotter pin- used to remove terminals from connector.
4. Small thin strip of wood (paint stick) or aluminum- used to hold terminals in place while you solder.
5. Small wire cutter (diagonal) pliers- used to notch the connector so the resistor can slide in.

1. Remove seat.

2. Find the fuel gauge connector under the right rear tank area. It will be a white nylon connector. Mine had black/yellow and yellow/white wires in it. Gently pull it apart. You'll see one side has male terminals and goes to the tank, and the other has female terminals and goes to the bike's harness. The one with female terminals is the one we will work on, since we want the mod to work in case the sender ever has to be replaced. Write down or sketch which wire came from which place in the connector.

3. Looking at the top of the connector, you'll see a small slot on the long side of each terminal. There is a brass tang on the back of the terminal that holds it into the connector. You want to press this tang down so the terminal will slide out of the connector. Using the small screwdriver or cotter pin, insert it into this slot and press/twist as needed. Once the tang is depressed, the terminal will slide out easily. Don't force it, you'll break the tang. You may have to do this a few times to get it right.

Here's the resistor I used:

4. With the terminals out, the next step is to insert the resistor. I snaked mine through the tabs that wrapped around the wire insulation and then under the ends where the male terminals fit. You want to leave enough lead so the assembly can be put back together- it does not take much. You could also wrap them around the metal part- hindsight being 20/20, I should have done that. You can then solder the resistor leads to the terminals. Make sure the solder is flowing- a "cold" joint here will make for an intermittent connection, a huge problem with electrical connectors. Some people report this mod not working and I suspect the problem is a bad connection for the resistor. No connection is perfect, but short of replacing the terminals and crimping & soldering in the leads that way, this is an acceptable means. I laid the terminals on a thin strip of scrap aluminum to support them while I soldered them. A paint stick would probably work here also.

5. With the nylon connector loose, you next need to cut a slot in it where the terminals go in. The ends are different, so make sure you do this on the open end where the terminals slide in. If any doubt, try & slide a terminal in and you'll know you are working on the correct end. Notch away just enough material for the resistor body to sit below the edge of the connector- like maybe 1/8" or so. If you take off too much, no big deal. If you don't take off enough, the terminals won't seat.

6. Gently pull the tangs back away from the terminals. If you bend them too much or too often, they will break- you only need the bottom away by about 1/16" or so. Line the tangs up with the slots- they should only go in one way, and they will only lock properly one way. Re-insert the terminals in the same holes they came out of using your sketch or notes. Use the small screwdriver or cotter pin to push them into place until you feel them click into position. Again, no great force is needed.

Here is the finished product:

7. Reassemble the connectors to each other, reinstall the seat, and test it out. Hopefully your gas gauge just got a lot more accurate.


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Re: C10 Fuel Gauge Resistor Mod with Pics, by "ZG1K"
« Reply #1 on: May 23, 2011, 11:27:16 pm »
Why does this work?


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Re: C10 Fuel Gauge Resistor Mod with Pics, by "ZG1K"
« Reply #2 on: July 16, 2011, 12:34:01 am »

The short answer is that by putting another resistor in parallel with the existing circuit, the total resistance is reduced.

The long answer is 10 weeks at the university...

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Offline gpzrocker

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Re: C10 Fuel Gauge Resistor Mod with Pics, by "ZG1K"
« Reply #3 on: July 16, 2011, 06:03:37 am »
Nice write up, thanks!

Offline Motor Head

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Re: C10 Fuel Gauge Resistor Mod with Pics, by "ZG1K"
« Reply #4 on: November 15, 2011, 08:22:00 pm »
 This is a quick do it yourself easy Mod. Nicely written, and easy to follow. Works quite well. I already had the resistor, so cost was like 1/2" of solder.
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