I have a Passport 8500 which is capable of displaying voltage. I also have a ScanGauge II which can display voltage. They both seem to match within 0.1-0.2 volts of each other. I notice in my Accord that majority of the time it's in the high 13's. On occasion it will go down to the low 12's. This usually only happens when I'm a lower speeds driving around town (slowing down for a stop sign or turn). At highway speeds it's always stays in the 13's. Is this just the regulator lowering voltage due to possibly lower loads when driving around town?
Fluctuating voltage normal?
- Thread starter gonefishing
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JHZR2
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Voltage is a function of speed and load. Bad grounds can also screw up the voltage.
The voltage fluctuation is normal for a Honda. They have an ELD (electronic load detector) located inside of the fusebox. The ELD controls the alternator output level depending on the load and operating conditions of the vehicle. Honda uses this system to save fuel.
If your alt/ battery gets warm the system voltage should drop to keep the battery from boiling over. Driving around town I could understand underhood temps being warm.
By this premise you should get a few 1/10s more volts on a cold morning.
By this premise you should get a few 1/10s more volts on a cold morning.
Some cars have voltage regulators that drop the voltage when the battery is fully charged and the car does not have a high electrical demand, such as in daytime cruising down the interstate with the radio shut off. My Cruze will vary between 14.1 volts and 12.5 volts depending on electrical demand.
I think posters above me have supplied the answer.
I think posters above me have supplied the answer.
Thanks everyone for the information. Sounds like this is normal behavior for a Honda. I might try an experiment by shutting off the blower and radio and see what the voltage does.
A good test ought to be sitting with the headlights on - engine off- for about 10 or 15 minutes and watching the voltage rise after starting the engine. It should rise to around 14 and then drop a bit after all the charge taken out is replaced. If it doesn't start creeping up right away, the system ought to be load tested. (Engine running, big resistor across the battery).
Yes, voltage will vary from idle to mid RPm or up.
Real voltage gauges should move depending on RPM and draw. On GM's the alternator cuts the voltage right down if the battery is fully charged, which you see since its a real gauge.
Is it also possible that the alternator output at warm idle is insufficient for the electical demand of the moment?
I ask because I noticed years ago while driving a 1996 Toyota Celica (1.8 with MT) at night with headlights on, idling in neutral coasting down to a stop when I hit the brakes the healights dimmed. I simply assumed that the alternator output wasn't enough at that RPM for the combined electrical load. That Celica was still driven by the same owner (not me) for many years after that, never had an alternator failure, and got five years service out of batteries.
I ask because I noticed years ago while driving a 1996 Toyota Celica (1.8 with MT) at night with headlights on, idling in neutral coasting down to a stop when I hit the brakes the healights dimmed. I simply assumed that the alternator output wasn't enough at that RPM for the combined electrical load. That Celica was still driven by the same owner (not me) for many years after that, never had an alternator failure, and got five years service out of batteries.
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