Battery warning override.
Working from the basic design offered by Jerry Fields web site ( http://facstaff.uww.edu/fieldsj/mcycle/Connect/) I set out to stop that confounded battery warning light once and for all!
Firsts, for those unaware of the situation, here is a short breakdown.
Originally the Seca was equipped with a small sensor that replaced one of the fill caps on the battery. This sensor held a probe that went down far enough into the battery to make contact with the electrolyte (battery acid) providing an indication when the fluid level started to get low.
Most batteries sold do not come with this sensor, and many Secas' now find themselves without the probe, and an annoying battery warning constantly illuminated on the dash.
My project was simply to bypass that sensor, and trick the system into thinking one was there.
Here is how I did it:
1 pkg 4.7k ohm, 1/2 watt resistors (Available at Radio Shack) *OR 1 pkg 2.2k ohm resistors.
1.) Find the Sensor wire, located near the battery. (White w/red stripe)
2.) I chose to solder 2each, 2.2k ohm resistors in series for 4.4kohms total resistance. (See note below), and then covered them with heat shrink tubing.
3.) Find a switched voltage source. Although the battery is right there, and one would be tempted to use it, I didn't want any possible battery drain while the bike sat, so a switched source made more sense to me. Like Jerry's example, I chose to use the tail light lead (Blue w/white stripe). I had to remove a little of the wrapping from the wire loom to expose the wires.
4.) Wire the resistor inline between the voltage source, and the sensor lead. You can use the crimp splices shown, I chose to solder mine, then wrap with electrical tape... Your call.... but solder will not corrode as quickly.
Using Jerry's recommendation of a single 2.2k ohm resistor, I measured the voltage drop, and saw that 5volts was what was being sent to the computer. In my mind, this is ok, as most digital systems of that era were 5vdc chips. However I experimented further by placing a second 2.2k ohm resistor in series (effectively increasing resistance to 4.4k ohms), and noted that even with only 1.5vdc going to the computer, the warning LCD still went out! An educated guess tells me that this system is most likely designed around sensing current flow, rather than voltage. Seeing that 1.5 volts worked just as well, I choose to leave the two in series, to avoid any possibility of over-voltaging the circuit. You could simply go buy a singe 4.7k ohm resistor for a cleaner install, but I had the 2.2k's already, so I made do.
It sure is nice not having to kill the warning light every time I start the bike!