Thread: Alternator Volts?

Hi pedro, I take it you are talking about your cranking battery?

If your cranking battery was not in a fully charged state before you went for your 45 minute drive then you could need to drive for up to 3 hours if the battery was low, or more, depending on how low the battery was.

Originally Posted by Pedro_The_Swift

Any ideas on D2 alternator volts,?
13.5? 14.5?
I installed a new alternator yesterday and after warmup TORQUE said 13.7 at the module.
after a 45 minute drive yesterday, this morning the batt V was 12.3.
I have had the battery load tested by the seller and all was good.
What else is there to check?

Hi, imo you should make sure you dont have some parasitic drain, quite common on D2s... just to rule it out... cos if the voltage dropped to 13.7 the presumption is that the battery was 98% charged, otherwise it should have been a bit higher(around 14.4)...but if it was charged you should have got a bit more voltage on the battery in the morning(14.7)...it's something tgo think about

hmm, when traveling, its around 13.7V, if you add the headlights it drops to 13.3.
shouldnt the alternator change to compensate for load?

where is your voltmeter connected, directly to the alternator output or in the interior fusebox? ... normally it must not drop below 13.5 whatsoever, and it must compensate when the load grows

Originally Posted by RAVE - Charging Operation

When the battery is at a low state of charge or the current draw from the
electrical functions of the vehicle causes a voltage drop, the alternator/
generator automatically charges at its maximum rate (dependant on rotor
speed) until 14-14.5 Volts is reached. When demand on the alternator/generator
falls, the current output is reduced.

so what stops the alternator changing output to suit demand?

it has a voltage regulator but as your's is new i doubt that it's the case... if the battery is charged the headlamps are not enough put the alternator into thios stage, switch on other consumers too for test(heated screens, main beam, etc), reas the description here Land Rover Discovery & Defender TD5 Series 2 Alternator Regulator 98-06 « Starter Motor Repair Kits Starter Motor Repair Kits

Each cell has 2.1 volts per cell. There are 6 cells in a 12 volt battery. There for a fully charged 12 volt battery is 12.6 volts. As long as the alternator is outputting more than it will be charging. I would have though the minimum for an alternator would be 13.8 volts. Check the alternator output with a multimeter then check to make sure you are getting the same reading at the battery. I would say your alternator is not the same as the original one it should also regulate the voltage when you turn accessories on. Turn them all one and check the same voltages as before. Long story short i wouldn't be happy with the reading you have if you are reading them across the battery.

All good info Jazzman,There are two part numbers for the D2,
The change is a different manufacturer.

This is the correct alternator.

but it would seem it hasnt solved the problem.