Why is my alternator hot?

[peaktorque]

I don't mean while the engine is running but whilst the car is parked.

I have had a power drain on the battery ever since I have owned the car (have to disconnect the battery when parked-up for long periods)

I have always put it down to the long deceased alarm/immobiliser, but have notice that despite the car being parked with the battery still connected for the past three hours and the engine is stone cold that the alternator is very hot.

Now it is obviously trying to become a motor and sapping power! The wires connected to the two main terminals and the link to the spade terminal on the alternator are all 12v.

Question is: Does the power have to be switched off to the alternator when the ignition is turned off, or is there an internal component within alternator to stop this happening?

The alternator works fine apart from this, although it is from a Range Rover and I was not 100% sure on the connections when I originally wired it up last year.

Thanks in advance

James

[Brap_Brap]

peaktorque said:

I don't mean while the engine is running but whilst the car is parked.

I have had a power drain on the battery ever since I have owned the car (have to disconnect the battery when parked-up for long periods)

I have always put it down to the long deceased alarm/immobiliser, but have notice that despite the car being parked with the battery still connected for the past three hours and the engine is stone cold that the alternator is very hot.

Now it is obviously trying to become a motor and sapping power! The wires connected to the two main terminals and the link to the spade terminal on the alternator are all 12v.

Question is: Does the power have to be switched off to the alternator when the ignition is turned off, or is there an internal component within alternator to stop this happening?

The alternator works fine apart from this, although it is from a Range Rover and I was not 100% sure on the connections when I originally wired it up last year.

Thanks in advance

James

It sounds like you've got power flowing through to your voltage regulator. This will cause a magnetic field
to be created in the alt. With any power flow comes heat. Try taking a measurement with a volt meter at your
voltage regulator and see if power is going through it with the key off.

This might explain it in better terms than I can. http://www.rowand.net/Shop/Tech/AlternatorGenerato...

Edited by Brap_Brap on Monday 25th May 16:42

[peaktorque]

Thanks........ this paragraph describing the charging light may explain:

There are several major drawbacks to this setup. One is that you have to to rev the engine up to approx 1100rpm once after the engine is first started for the alternator to begin charging - the alternator has to reach a high enough RPM so that it "self-excites". Another is that the field connection inside the alternator can allow a small current draw while the vehicle is not running, and this can cause a dead battery if the car is stored for a period of time. Lastly, you do not have the advantage of the remote voltage sensing feature and that means poor electrical system performance - dim headlights, slow wipers, and various other maladies

it's not connected is it! (never bothered as the bulb had blown anyway, didn't think it was that important)