isalos

Hello, I recently upgraded my regulator with a new Bosch one (made in China). The car is steady at 14v more or less but if I have AC on, when the fan in front kicks in, I have a 2v drop as seen here:



After 2-3 seconds it climbs back at around 14v.

If I have the heating window on as well as high beam lights, volts are at 13.8v, the drop goes down to 11.9v and then it stabilises at 13.2v...

Faulty regulator out of the box? With my previous regulator I was at 13.2 all range...

Mike Murphy

What was wrong with the OEM regulator?

Sometimes the voltage increases or drops depending on the battery’s charge level. It’s not like the old school regulators where the target voltage is always 14-14.4v. That level of voltage, over time, weakens the battery. It’s better to put higher voltage of 14-ish and then back off once the battery is charged to 13-ish, which is what the OEM regulator does well.

In either case, old or new, what you are seeing is probably normal (not an issue).

isalos

It was 22years old. the teeth/legs were down and it would pop an alternator problem on the dashboard. the car would be steady at a slow charging at 13.2v. with the new regulator, it went up to 14.10v.

My mechanic said that probably the copper side of the alternator (where the teeth/legs touch) may need some cleaning with sandpaper as well, due to the shape that has taken all these years.

DBJoe996

If I had my 25 year old alternator out, I wouldn't replace any part of it. I would buy a new Bosch alternator, install it and move on. I made a mistake a long time ago by installing a rebuilt starter. It busted in less than a year. Installed a new Bosch starter and it has been good for many years. Live and learn...

De Jeeper

Yea i probably would have replace the entire alt too but a new regulator can work well if the bearings and stator r still good.

U will always get a voltage drop when high amprage items kick on and the system does recover. I would drive the car for a few hundred miles and let the brushes wear into the stator. They probably r not making full contact yet.

996-CAB

Your symptoms are consistent with a corroded Y cable, the one that delivers current from the alternator to the starter and from there to the battery. Part number is 996-607-019-xx. The wire from the alternator is swedged to the wire that goes eventually to the battery. This connection is not weatherproofed and over time, it corrodes, creating resistance to the flow of current. As more things turn on, e.g, fans and lights, the more current is drawn, there is voltage drawn to the corrosion hence you see 11.9V at the battery. The other 2 volts are in the corroded cable.

If you can pull out the alternator, you should be able to the see the wire. It looks like this when it is bad. It is the end connected to the starter.

isalos

all great answers, thanks. indeed a new alternator is better than an old one, but ours, is a serviceable part, used heavily by many cars in tha VAG group. Hence my decision to change the regulator. I will check the cable and report back, probably brushes need indeed to settle.

is it an engine out to replace the y-cable?

996-CAB

Negative. It can be done without even lowering it. I've been told that if you snake the cable in from the side where it mounts to the +Jump point to the right of the power steering pump, it is easier than if you connect the alternator and starter and feed to from there out to the jump point.