4x4 / Off-Road TechThis section contains all discussion related to taking the FJ Cruiser in Off-Road situations, 4x4 applications and any armor modifications.
I've spoken to him many times, but we're still not exactly sure what's going on. However, I do know that my alternator likes to put out 13.2v sometimes and this is not high enough to trigger the LED to come on in the hell roaring.
The biggest question I have now is, if the car has little or no load will the alternator pull back it's voltage for some reason? The cases in which I've seen this the vehicle has been running for awhile and everything is fully charged with a small load on the vehicle. The dealer claims 13.2 is within spec as well. So I'm not sure what else to do from here. I could take it to the dealer I guess and have them test it.
Spincycle - You've never noticed the LED going out on it's own sometimes? Especially after long trips and lots of driving?
If it's easier to understand. I like to use the analogy of Electricity to Water which is easier for some folks (including myself) to understand. Consider Voltage similar to Pressure (as in psi/pounds-per-square-inch) and Amperage similar to flow rate (as in gpm/gallons-per-minute).
When the battery (the storage tank) is discharged to start the engine, the alternator (the pump) puts out as much flow and pressure as it is designed, to quickly refill the tank (battery) to it's designed pressure and volume.
Once the battery is refilled, the alternator (actually the diodes often referred to as the Voltage Regulator) cuts back the pressure and the flow to meet the needs of the electrical system. So it's not unusual to see 14.7-14.5 volts immediately after initial startup and then after a few minutes, if nothing else is drawing an electrical load except the drivetrain and it's computers, then you may see only voltage in the low 13's. That would be with a fairly new/good battery and little to no load (maybe no DRL's), etc...
In an automotive alternator, voltage is directly related to amperage so when the diodes regulate the voltage(pressure), they are in turn also regulating the amperage(flow).
DEWFPO
__________________ 2007 FJ, 5AT, Sun Fusion Yellow, CQ, UP, GY, RB, 2Q, EL, VS.
"Wanted - young, skinny, wiry fellows, not over 18. Must be expert riders willing to risk death daily. Orphans preferred"
Original newspaper add placed by William Hepburn Russell, founder of the The Pony Express
Seems odd to me. I would think the regulator would keep the voltage high unless it was overloaded, THEN it would reduce the voltage in order to regulate the demand a bit. It seems as if it has a mechanism that turns down the voltage anyway if there is little to no demand as well.
Seems odd to me. I would think the regulator would keep the voltage high unless it was overloaded, THEN it would reduce the voltage in order to regulate the demand a bit. It seems as if it has a mechanism that turns down the voltage anyway if there is little to no demand as well.
The alternator is an on-demand pump. That means it only makes as much as it needs to keep the battery charged and accessories firing. That's why you might see the headlights dim for just a second when you turn on those big driving lights until the diodes recognize the voltage drop and tell the alternator to pump out more juice. It takes fuel to drive the alternator so it is a very efficient pump in that it doesn't make any more electricity than it needs to or can.
DEWFPO
DEWFPO
__________________ 2007 FJ, 5AT, Sun Fusion Yellow, CQ, UP, GY, RB, 2Q, EL, VS.
"Wanted - young, skinny, wiry fellows, not over 18. Must be expert riders willing to risk death daily. Orphans preferred"
Original newspaper add placed by William Hepburn Russell, founder of the The Pony Express
Engine on pretty much any time. Idle, moving, whatever. Is your light always on when your engine is running?
My BIC is currently uninstalled until those folks in the dual-D35-battery tray thread get off their asses and start melting metal to sell me, but My recollection is that it was on during engine-on operations.
This was with the newsest 300A model Mike sells, bought from him last spring.
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'07-6MT-FJC...and a whole BUNCHA stuff.
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My LED never goes out with the engine running. My scanguage never goes below 13.4 volts however.
It sounds like the HR module was just not set up for a lower voltage alternator. You could replace your alternator, but could get another "spec" 13.2 volt edition.
I suspect that both of your batterys are fully charged even with the intermittent function of your system. If one was not fully charged, the alternator would require more output which would engage the module. Once full charge was obtained, the voltage would drop off and the module would cut out. As your batterys age, they will require more charge time, and I bet this problem goes away. If both batt remain fully charged now, I would just let the HR module cycle if it wants to--no harm.
An interesting aspect of the 300 amp hellroaring I didn't fully understand before is that it's only a one way block. It isolates the starting battery from the main system/battery, but not the other way around. The only thing that the system does in automatic when it's engaged is enable a diode bypass so you see full voltage to the backup battery (otherwise you have to overcome .7v of the diode voltage drop). One condition I'm curious about right now is if the backup battery required charging but the main battery was full and there is low load on the system. Will the alternator see that load anyway or will it have to first reach a higher voltage because of some load on the main system to activate the diode bypass?
chicken or the egg kind of thing. Maybe this isn't a problem, but I haven't reasoned through how that will work yet.
2007 FJ, 5AT, Sun Fusion Yellow, CQ, UP, GY, RB, 2Q, EL, VS.
"Enjoying the Journey"
Linear Mode
