Battery Charging problems

From engines to interiors , have you a question or can you help, ask and answer here !

Moderators: desertstorm, water01, vwnutant

Post Reply
Renesis
Posts: 4
Joined: Sun Apr 24, 2016 2:32 pm
Passat model: B5.5

Battery Charging problems

Post by Renesis » Fri Nov 08, 2019 4:28 pm

Bit of background info, my car is a 2005 1.9tdi Passat and has approx 180,000miles on the clock with, I assume, the original Valeo alternator.

I was driving to work today via a different route and didn't notice a speed bump in the road which had not been painted yet (the small square bumps, not the large ones that span the road). Unfortunately I was carrying a bit of speed because of this, and hit the speedbump with some force. I heard a clunk - as if the bump had hit the underneath of the car.

I pulled over to have a look underneath and all seemed well so I carried on. About 2-3 minutes later, the battery light came on - checking voltage at the battery posts, I'm getting 12.5v at idle. When I accelerate hard to 2-3krpm the light goes out and the alternator starts working (based on interior lights getting brighter), but the millisecond I let of the pedal, the light comes back on again.

I bought a brand new battery 6 weeks ago, and in the time I have owned the car (5ish years) I've never had any issues with charging. It makes me think the bump has caused/knocked something but could this be a failing alternator / voltage regulator? All connections behind the alternator look sound, but I have no idea where the earth strap is in the engine bay (or if there's multiple) so just wanting to make sure there's nothing I need to rule out before shelling out for a new alternator/regulator.

Cheers all

howey
Too much time on your hands
Posts: 2909
Joined: Sun Aug 16, 2009 11:12 pm
Passat model: B5

Re: Battery Charging problems

Post by howey » Sat Nov 09, 2019 1:08 am

Most likely the alternator pulley but at those miles a new unit with pulley may be more cost effective

Renesis
Posts: 4
Joined: Sun Apr 24, 2016 2:32 pm
Passat model: B5.5

Re: Battery Charging problems

Post by Renesis » Sat Nov 09, 2019 11:30 am

Update:

After conceding that I may end up having to pay £100+ for a new alternator, I thought I have nothing to lose by checking out the voltage regulator. Worst case scenario, I lose the ability to charge at whatever the RPM until I get it changed.

Using nothing other than 7mm+13mm sockets, a soldering iron and about 15 minutes, I took of the voltage regulator and saw one of the brushes had broken off and the other had worn down to almost nothing. I had some replacement bushes off eBay (£2) already, fitted them just now and battery light has vanished, and the car is charging at 14.1v. Couldn't believe how easy it was, I didn't even need to take the alternator out of the car and it was all done in situ.

I fully recommend everyone check out the voltage regulator before replacing their alternators, its very much a DIY job even for beginners. If you don't want to solder two wires, you can always replace the regulator whole for about £20.

Post Reply

Who is online

Users browsing this forum: No registered users and 28 guests