Thread: Alternator Over-voltage issue

Originally Posted by josh.huber

The body control module should control the voltage from the alternator.
Do you have a scan tool? Gap or similar. Does the voltage on the scan tool match that of the multimeter on the battery.
If you had a bad connection to the module that controls battery voltage this would spike your battery voltage.
Also if you have a scan tool. Reset your battery. If not the alternator might be trying to "boost" the battery back to life. Mine did this. Was over 15 volts on a down hill run. Way to high for a good battery. Are you sure you got the wiring right? I commentated on a post a long time ago where the owner replaced that same plug and wired it wrong. Was easy to do. The schematic he followed wasn't 1, 2 , 3 was 1 , 3 , 2 and caught him out. Ill find it

I have a scan tool. All of the relevant voltages on the tool look consistent with the multimeter on the battery.

I guess this means that the ECU/ECM knows that the voltage on the battery terminals is exceeding 15v.

Once the voltage becomes excessive, the first noticeable thing is a flickering of the instrument panel backlighting (noticeable at night only), followed by the shutdown of the media amplifier (although the head unit controls continue to act as normal), after this the Transmission usually faults (with an excess voltage error code), and then all the other control modules seem to fault simultaneously following this, lastly followed by the ECM, at which point, everything electronic stops.

Can you or did you do a battery reset?

Originally Posted by josh.huber

Can you or did you do a battery reset?

A couple of mentions of this. I have not done a battery reset.

Ive seen that the D4 has the battery monitoring system, but i cant find any mention of it for the earlier model year D3s.

Yeah I'm notup to date enough with this on d3's to know that. I didn't read the D3 bit. I know it made a big difference on my D4 .

Have you got a photo of the of new pig tail before you joined it into they harness. Has the as pin 1 got battery voltage before the car starts and does it have battery voltage once the car is running.

Did you bare back plenty of wire before crimping those red joiners in?

Paper clips make good tools into those harness plugs .

Where are you, I seen Chichester. Send us a pm you might not be that far away

Originally Posted by josh.huber

Have you got a photo of the of new pig tail before you joined it into they harness. Has the as pin 1 got battery voltage before the car starts and does it have battery voltage once the car is running.

I don’t have a photo, but checked it lots of times. Pin 1 is the bat sense and has power both before and after starting the engine. Power is lost when removing the F20E 5w fuse.

Originally Posted by josh.huber

Did you bare back plenty of wire before crimping those red joiners in?

Yes. I’ve also cut off the connections and reconnected just to be sure. Today I ran a continuity test from the alternator connector to the ECM harness connector for both PWM wires and didn’t find issues.

Originally Posted by josh.huber

Where are you, I seen Chichester. Send us a pm you might not be that far away

I'm on the Gold Coast. But the issue began with my drowning the alternator at Chichester. Thanks a lot for the offer though, it’s driving me crazy.

You need to measure the power at pin 2 with it running to see what the ECM is commanding.

So you have the factory Brown wire crimped into the terminal furthest away from the main battery cable?

Originally Posted by josh.huber

So you have the factory Brown wire crimped into the terminal furthest away from the main battery cable?

yes. Then the red/white in the centre.