Originally Posted by texdog
Nippon Denso alternator, GRT, occasionally I get a 2 volts yellow flash warning, it doesn’t stay longer than 4 or 5 seconds. What is it? EFIS voltage is 12.8 to 13.0, EFIS voltage for alternator is 13.5 to 14.2. Thanks,
I assume the light (which is yellow) is a discrete light in your panel wired direct to the ND alternator. EFIS (internal voltage)/Alternator voltage (Bus voltage) is OK or normal as shown on EFIS when light is on... correct?
Not a lot of info to go on. ND alternators typically use two, three or four total wires in their installation. Big B lead or battery lead is always connected. Then there is a plug, which may use one or more wires.
(See link here) https://www.toyotavantech.com/forum/...4&d=1438025502
The IGN wire is typically always used and tells the alternator to wake up or sleep (do not cycle off/on when engine is running).
The "L" wire for voltage warning light.
The "S" wire is not available on some models.
The "S" wire is a sense wire, where the regulator is monitoring the voltage. Otherwise voltage is monitored by the IGN wire (or B wire on some models).
13.5V (bus voltage) may be triggering your low voltage light. 13.5 volts is fairly low. Typical alternator range is 13.8 to 14.5, although 13.5 volts may be OK for short periods. You need however 14.2 volts to charge a battery, especially with AGM batteries. You need about 1.8 to 2 volts higher than battery voltage to charge battery quickly. (Bats are about 12.6 volts). However once charged 13.5 volts on bus is OK to keep battery charged or trickle charge.
Is this happening at idle, low RPM? Does it go away when you increased RPM? It could be normal if RPM related.
Check, for bad or loose connections on the IGN wire or "S" wire (if that is being used). Check all connections are snug, connector to wire termiinals are secure. If crimpled pull on them. Some times the only thing holding them on is the plastic insulation. In doubt re-do the connectors and check the ND's plug terminal contacts....
EFIS 12.8 volts (I assume internal to EFIS only) is low but likely normal for EFIS which has it's own voltage regulator.... Read your manual to check that is the case.
It could be the ND's internal voltage regulator is having an intermittant problem and may be on it's way out.