Overcharging Alternator

**MacFamily** · 30th July 2010, 04:59 PM

Ive replaced the alternator on the 300tdi defender two days ago and today the missus was driving it and the Luna dual battery monitors alam was going off and both main/deep cycle were flashing overcharged.

Now its a new Lucas

65 amp and they replaced the pully with my old one.

Now I wired it the way they said both wires to were ive circled it red and the battery warning light on dash circled yellow.But it was overcharging and my volt meter died so cannot tell what volt's it was supplying but it was above 14.4 thats the max on the monitor.

Now I rewired it to were you can see the blue circle but when iam on the open road doing a 100kays it just bearly reaching 13.7 and when at idle reducing to 12.6.

Both batteries are fine so is the resistor in the alternator stuffed or bad earth or have I just stuffed up.When it was overcharging the alarm was going off when you got the revs high or at 90kays + .

Ive done a search but cannot find much.

If anybody could help would me much appreciated.

**justinc** · 30th July 2010, 05:05 PM

What are the letters next to each terminal? There should be some stamped on the casting next to where the terminals come out the back of the alt.
Too late now, but I would've upgraded to a Disco one as they are 100A. 65A isn't enough for deep cycle battery charging, driving lamps and accessories etc IMHO.
JC

**MacFamily** · 30th July 2010, 05:13 PM

Originally Posted by justinc

What are the letters next to each terminal? There should be some stamped on the casting next to where the terminals come out the back of the alt.
Too late now, but I would've upgraded to a Disco one as they are 100A. 65A isn't enough for deep cycle battery charging, driving lamps and accessories etc IMHO.
JC

Theres nothing stamped on the casting, cause i looked at that too.I was going to upgrade to a 100amp but the boss needed the car and only had one afternoon after work to fix it.

**MacFamily** · 31st July 2010, 05:19 PM

Well still no closer to solving this problem have rewired it back to were auto elec told me too (circled red) B+?

You will notice there is a red wire with a fuse its connected to both relays that are for the headlights which the previous owner installed to stop the headlight switch burning out.

Now when you get to 100k and the dual battery alarm and lights are going off overcharging turn the lights on it stops.....

Also the main battery seems to be stuffed may have cooked it, when the car is not running and I turn the lights on it goes from 12.6v to 12.0v

If the new battery dosent fix it then will take it back to auto elec, maybe a faulty regulator.

I might have to check the earth from engine to chassie

**MacFamily** · 2nd August 2010, 05:41 PM

Well all fixed took alternator back for auto elec to do a bench test and regulator was faulty.

Yesterday when I was trying to find the source the volts got up as high as 15.73

I took the batteries down to battery world and they tested all Ok

I can now change a alternator in 30min tops

Thread: Overcharging Alternator

Thread Tools

Overcharging Alternator

Bookmarks

Bookmarks

Posting Permissions