Clock & Trip Meter Power

[Constant Mesh]

Does the power for these come exclusively from the Backup fuse?

On my '04 there are two power inputs for the meter display. One is from the switched Ignition fuse and the other the Backup fuse.

I haven't checked it but I'm wondering if I pull the Backup fuse will the clock and trip meters stop working with the Ignition fuse powered? Do they normally default to the Ignition fuse when it's powered?

I've been experiencing a clock and trip meter reset during occasional hot starts. I probably need a new battery but I was considering adding a simple circuit to keep the clock and trip meters powered when the bus voltage sags during problem startups.

If I support the Backup fuse circuit with an auxiliary power source (capacitor) will the clock still go away when the Ignition voltage sags?

I guess I'll just have to pull the Backup fuse and find out.

 

[Fred W]

The circuit in the instruments powered by the backup fuse could not also be connected to the switch 12V power or it would back-feed that circuit when the power was switched off.

Adding a capacitor will not prevent the backup voltage from sagging during starting. You already have a giant capacitor installed (the battery) and it is sagging, why wouldn't a much smaller electrolytic cap do the same thing?

Your best bet is to just suck it up and replace the battery now.

 

[mcatrophy]

The backup supply powers the clock and trip odo.

[edit] Fred posted just before me, I agree with his assessment, unless you want to start playing diodes and suchlike. Not worth it, suck up and replace the battery (having checked all the relevant connections and stuff).

 

[RossKean]

I agree that the battery most likely needs replacement as your best option BUT it is worthwhile to check out the current draw on starting! A starter motor that is going bad may cause a similar voltage sag as it will draw very high current as it attempts to start the bike. Check out the amps drawn during cranking before you replace the battery (clamp-on DC ammeter).

 

[ionbeam]

Specifically, because you have --->

...been experiencing a clock and trip meter reset during occasional hot starts...

You should really --->

...check out the current draw on starting! A starter motor that is going bad may cause a similar voltage sag as it will draw very high current as it attempts to start the bike...

If your FJR is drawing >80 amps on cranking it's time to put together a battle plan to deal with a failing starter motor.

 

[Fred W]

So, the OP can either go out and buy a clamp-on DC ammeter or replace his tired old battery to determine if the starter motor is bad.

Just sayin...

 

[Constant Mesh]

I've replaced the battery twice since I bought the bike new. Each time I experienced the same hard starting when hot with the old weak battery. A new battery fixed the problem.

It seems that a hot start puts the most stress on the starting system. If you have a weak battery it really gets exposed on a short shutdown hot start.

I can easily add a capacitor and isolate it from the rest of the system so it will power the clock and trip meters during cranking. One diode is all that is required. The clock and trip meter electrical load is less than 0.002 amps. A small capacitor can easily supply this for the seconds long short bursts of the starter.

 

[Fred W]

I've replaced the battery twice since I bought the bike new. Each time I experienced the same hard starting when hot with the old weak battery. A new battery fixed the problem.
It seems that a hot start puts the most stress on the starting system. If you have a weak battery it really gets exposed on a short shutdown hot start.

I can easily add a capacitor and isolate it from the rest of the system so it will power the clock and trip meters during cranking. One diode is all that is required. The clock and trip meter electrical load is less than 0.002 amps. A small capacitor can easily supply this for the seconds long short bursts of the starter.

So, you have benefited twice previously from the clock and trip meter resets giving you an early warning that the battery is about to crap out, but you don't want that early warning any more?

 

[ionbeam]

So, the OP can either go out and buy a clamp-on DC ammeter or replace his tired old battery to determine if the starter motor is bad.
Just sayin...

Where did I say that? I suspect that there may be more than just that one way to have the starting current checked.

Just sayin...

 

[Fred W]

You didn't say that, I did. (Ross was the one who mentioned the clamp-on ammeter)

My point is that it is a pretty good bet that the battery is the cause, and it's easy and relatively cheap to swap out. If he finds it's not the battery then it's time to start rounding up tools that he is unlikely to have on hand and do some diagnosing.

 

[RossKean]

Or just eliminate (or confirm) the battery problem by getting it load-tested for free. AS Fred mentions, the clock/ODO reset is a pretty good early warning indicator. Eliminating that feature is a bit like putting a coat of paint over a rusty body panel on the car. Might be something to do if trying to sell it to some poor unsuspecting buyer but not doing yourself any favor in the long run if you decide to keep it. Note: Frequent high-current draws on a battery will significantly shorten its life.

Since when is it a bad idea to get more tools? Being the cheap ******* that I am, I would probably manage to borrow an item that I would use very infrequently.