'80 1100SG Gas Tank Sensor Failure

[scott0757]

it's spring and time to fix things on the Special. Rebuilt brake master cylinder and calipers, changed valve cover gasket today , but now want to fix the fuel warning light (not fuel guage) that stopped working a few years back. The manual says the sensor should read somewhere around 1,500 ohms, and mine reads more like 1.5... If I short the 2-wire connection that would hook to the sensor, the gage light comes on.
So I think this sensor is toast, but I am having trouble locating a replacement.

Any suggestions? I can find new gaskets for sale, but am reluctant to pull it if I cannot get a replacement.

[TopCatGr58]

Hey Scott,

The special fuel sender unit is a THERMISTOR, but I don't know the resistance value.

Here's an advert on eBay about repairing/replacing the thermistor on the sensor, a little pricey, but the seller says they will provide the proper version to match the ohmage requirement!

http://www.ebay.com/itm/REPAIR-Your-...-/220677307066

Perhaps some of the electrical gurus know the Kohm value, and so you can then get a much cheaper thermistor??

T.C.

[scott0757]

Thanks

Thanks TC for the lead. I have messaged the seller. Will see what happens. All in all cheap if it fixes the problem.

[bikerphil]

I have repaired them before by opening up the can that contains the thermistor and soldering in a new 1K ohm NTC thermistor.

[MadHatter4119]

You might be able to find another senor from another bike...check your local
bike salvage yard...Do what Bikerphil said...google them...they cost under
$2.00 in most cases...cheap...Might be able to pick one up at Radio Shack...?

[scott0757]

May try that but Radio Shack stores have almost all closed in this area. Very sad for us DIYrs. Will try and locate some nearby...

[MadHatter4119]

Yea...it all throw away electronics these days...I noticed a big change in
Radio Shack in the last 10 to 15 yrs...Its hard to even find a TV Repair Shop
anymore...25 yrs ago...they was all over the place in my area...Can't find a
one now...

[bikerphil]

If you google "thermistor ntc 1k ohm" you will see them. An axial type would be best but a radial type may be used, it just takes some creative bending of the leads.

[scott0757]

ten on order for $2.79. Give me a few attempts!
Stay tuned!

[scott0757]

As the OEM thermistor is encased in a metal can that it looks like I have to cut open and replace the thermistor, rewire it so one lead is soldered to the bracket and the other to the other pin in the sensor plate.

Is that can required to be sealed with something gasoline will not disturb? Mine appears to have small holes in the base plate where the current lead goes into the can. I got the typical pancake style thermistors and wondered if they hold up in gas?

Any others that have replaced the thermistor, what did you do?

[bikerphil]

What I did was pry the little can open. One end has a lip around it that can be bent up all the way around so it can be opened and then crimped back down later after the repair. No need to use any adhesive.
I tested a single thermistor in gas first for a few weeks to make sure it would hold up.

[scott0757]

Sensor repaired. Next for the install on the tank and the real test...

[bikerphil]

I tested my repaired sensor in a cup of gasoline and wired it up to he bike's harness plug to make sure it worked the light in the gauge properly. Good luck with your repair.