Strange Voltage Problems

Michael666 · Post by **Michael666** » 31 Jul 2018, 08:04

I'm really struggling with my Volvo T6. I've been told by the previous owner that the car runs fine, despite the Battery warning being displayed. He tested it. I stayed with it and sucessfully covered more than 6000km without any issues. 2 weeks ago when i filled up and left the petrolstation all hell broke lose. I got a warninglight bingo, the rear window heating turned on and all fans went full power (Engine and interior). The message was "Overvoltage, pull over safely" So i did. Today i got around to changing the alternator regulator (the one that was in there was put in as an effort to get rid of the battery warning by the previous owner). Eveerything went well and the first enginestart and idle was all fun and smiles. 14.2V at the battery. Great. Went for a testdrive a few minutes later...battery warning came on....11.98V at the Battery at idle -_- Still took it around the block...put it in manual and drove around in high rpms. Light went off and 13.8V. Only to come back on again and even the high rpm pulls didn't get rid of it. Still 11.9V
Has anyone had this problem? Am i missing something? Any help would be really appreciated!!

Sorry for the long story

Post by **RickHaleParker** » 31 Jul 2018, 08:56

Have the battery bench tested. I'm getting the impression one cell is dead or it is not taking a charge.

Post by **matthew1** » 31 Jul 2018, 09:19

Rick, I made your account MVS Contributor level. You've provided immeasurable help to owners.

Sorry for the thread hijack.

Post by **oragex** » 31 Jul 2018, 09:32

RickHaleParker wrote: ↑31 Jul 2018, 08:56 Have the battery bench tested. I'm getting the impression one cell is dead or it is not taking a charge.

Also inspect the cables near the alternator, battery and fuse panels (corrosion, cracks)

If all checks fine, measure the battery, here's a long-ish video that explains a few things www.youtube.com/watch?v=0gc1SCGLfCk

Keep in mind that it's always possible to have installed the wrong regulator (several variations available, also stay away from no name regulators)

Post by **RickHaleParker** » 31 Jul 2018, 10:17

"also stay away from non name regulators"

My dad had a name for them, Break-a-leg-er ... good luck!

Post by **mrbrian200** » 31 Jul 2018, 12:26

If it turns out the battery tests good, it might be worth performing voltage drop tests across the main battery cables between the battery and engine compartment/chassis.
You'll need a long wire to span the length of the car to use with your voltmeter.
From what I understand if there's resistance across these cables it can reek havoc with everything.

Michael666 · Post by **Michael666** » 02 Aug 2018, 10:53

I've tested a bit more. I guess it's the alternator. It only put out 11.6 Volts at idle. Mesured from the Positive to Alternator case.

Post by **RickHaleParker** » 02 Aug 2018, 10:55

From the Positive battery terminal or the Positive output on the alternator?

Michael666 · Post by **Michael666** » 03 Aug 2018, 11:33

RickHaleParker wrote: ↑02 Aug 2018, 10:55 From the Positive battery terminal or the Positive output on the alternator?

Measured from the positive output on the alternator. Currently I took out the battery and I'm slowly (4A) charging it. But i don't think that the battery is the issue...

Post by **RickHaleParker** » 03 Aug 2018, 12:44

Sounding like it is the alternator and/or voltage regulator. The Voltage regulator is under the end cover and is replaceable for ~10% of what a OEM alternator cost.