2002 S60: alternator/voltage regulator going out (or computer issue)?

moonweasel · Post by **moonweasel** » 28 Feb 2020, 10:31

Hey all

Here is my situation — would love to hear your thoughts:

Battery light came on while doing a high-rev acceleration up an uphill freeway on-ramp
The next time I drove the car, the idle, headlights, and all instrument lights were pulsing/dimming, all together, about once or twice per second. This now happens every time I turn the engine on
I eventually discovered that if I rev the car up to around 3,200 rpms for a couple seconds while in park, the pulsing STOPS until the next time I start the car
Voltage across battery terminals is around 12 with engine off, pulses between around 12-14 when engine is first started, and sits around 15 with engine running after revving the engine to “reset” the pulsing (voltage values very approximate as I am currently limited to an analog multimeter with a scale of 0–50V)

Does this sound like a bad alternator, and/or voltage regulator?

Or since the battery is getting charged and the issue can be temporarily “fixed” by the revving, is it a computer issue that can be reset somehow?

Post by **oragex** » 28 Feb 2020, 12:39

How many miles ? Hard to be 100% sure, but I would bet on the regulator. Remember that a poor battery will also take down the regulator, because the alternator will keep the maximum voltage at all times as the battery can no longer be fully charged, which overheats the regulator and causes it to fail in exactly the same scenario of a longer rev - mostly during summer times, but I guess at some point the temperature won't matter. So if you replace the regulator, drive with it a little then test the battery see how if it accepts a good charge

You can replace the regulator without removing the alternator from the car, but after removing it from its bracket

Also test the alternator pulley and clutch. Test the other pulleys as well while the belt is off

If you want to remove the alternator, undo the ps pulley and the upper rad hose

Regulator for your 20002 https://www.fcpeuro.com/products/volvo- ... 51#fitment

moonweasel · Post by **moonweasel** » 28 Feb 2020, 16:59

Thanks for the reply, oragex!

I’m at around 122k miles.

Follow-up questions:

Right now the battery appears to be holding its charge just fine — does that affect your guess at all?

And just so I can better understand — what is it that makes you think it’s just the regulator, as opposed to the whole alternator? I understand nothing is guaranteed but would like as much as possible to narrow it down so that I don’t replace the regulator only to find out I should have done the whole thing while I had her open…

Also I have read posts where people talked about only needing to clean or replace regulator brushes rather than the whole part — any thoughts on that?

Post by **oragex** » 28 Feb 2020, 17:17

Usually, the alternator fails in two ways: either electrically at the regulator (bad diodes or worn brushes got too short, perhaps less than 5mm long), either mechanically at the bearings or pulley clutch. I haven't heard about the alternator coil to fail on these cars, perhaps possible on other brands.

The brushes are not serviceable on this unit - also, it's hard to find good quality brushes, I did look some times ago on Internet, most Ebay chinese ones are poor quality

The battery light would mean the voltage was too low, under 13.5V. Pointing the regulator is just a guess, a failing one will throw a battery light. The other way would be bearings or the clutch about to seize which would cause the belt to start slipping - you would notice wear on the belt and perhaps some burning smell. Possible also to feel some engine power loss.

It's also possible some other pulley on the belt is about to seize, which would slow down the belt - good to test the compressor and the tensioner pulleys.

May try to get one of these, it helps reading the alternator (but not the battery), gives the voltage in real time www.youtube.com/watch?v=IVDHzTkjHlc

IslandV70 · Post by **IslandV70** » 02 Mar 2020, 10:25

15 volts is too high!
The regulator is certainly one thing that can go wrong, but before you get into that check all connections. A loose connection to the battery or ground can induce similar shenanigans. My old Starion did something similar when the ground wire to the battery started coming loose.

moonweasel · Post by **moonweasel** » 03 Mar 2020, 23:35

I think my multimeter is not giving accurate readings. I’m ordering a Bosch regulator and will check the battery after it’s installed.

moonweasel · Post by **moonweasel** » 03 Mar 2020, 23:40

IslandV70, I checked the connections at the battery in the trunk — where else should they be checked?

IslandV70 · Post by **IslandV70** » 04 Mar 2020, 10:12

At the engine end too, especially ground wires.

moonweasel · Post by **moonweasel** » 06 Mar 2020, 16:35

Will do—thanks again IslandV70.

As an update, if anyone is interested: I got a digital voltage reader like Oragex suggested:

The battery voltage with the car off is indeed reading low: around 10.4V

When I turn the car on and it is "pulsing," it is pulsing between around 10.8V and 13.8 or 14V, back and forth, back and forth.

When I rev up to 3200 rpms for a few seconds and then let go, it then remains steady at around 14V, until the car is turned off and re-started, at which point it does the pulsing until I rev again, rinse, repeat.

However the car also died on me twice this week while driving, and I had to jump it to get it started again (and I'm sure that's why the battery had any voltage at all).

I now have the replacement Bosch voltage regulator in from FCPEuro, so will give that replacement job a go if I can get a break from the rain (Northwest Washington state here…)

Post by **oragex** » 06 Mar 2020, 18:14

Good update. Don't forget to test the battery with the new alternator, faulty alternators damage batteries and the vice-versa is equally true