Last night my 'battery' idiot light came on.

I was doing a pretty good pull to get into traffic on the highway.

The light came on, I pulled over to check things out, by the time I got the car stopped the light was off again.

I did poke around but really what are you going to 'see' with regards to the charge light coming on?

Anyway, I realized, standing in that parking lot with a flashlight poking around under the hood with my wife in the pass seat (all those with a similar memory raise your hand) when it occurred to me that I don't know much about the electrical setup on these newer machines.

On my old 760 there was an built-in, but easily changeable voltage regulator that turned out to be the problem in 99% of the problems I ever had. They would die and either the alt wasn't charging enough or it was charging too much.

Since my car doesn't have a volt gauge, I was wondering if anyone out there has any ideas about what might have happened, and what I can do in terms of preventative maintenance on my charging system.

I'm leaning towards an 'over-charging' fault, as I just got done with a very very cold winter here in NB Canada and I never had a problem with the electrical system before. I don't know the age of the battery for certain but I believe it was new when I bought the car from a friendly mechanic in September....

Any ideas about what might be wrong?

How about the component layout? I can see where the alt is - where is the voltage reg?

How about common failures? I haven't read anything about charging system problems on this board before...

Thanks for the replies everyone.

I've got some more information to share.

First, I have found a guy locally who has stripped a couple of 850s for parts and has at least one alternator I can buy from him cheap. I actually think you guys are right and it's my belt, but I'm not accustomed to not having spare parts like this around so I might pick it up anyway if he'll let it go cheaply. I have a question on this though. If one of them is OEM (Bosch I think?) and one is aftermarket, should I go with the probably-older-but-probably-better-quality OEM one, or the slightly-worse-quality-but-probably-newer-and-less-miles aftermarket one? Any advice?



Second, I finally got a volt meter on the thing last night. It actually seemed okay in the driveway - the battery was giving me ~12.5 with the car off, and with the car running I was getting ~13.8, so not /great/ charging power, but not bad.

Everything seemed fine for the first little bit of the drive too, staying between ~13.5 - ~14.5 volts.

Then all of a sudden it just went down to ~12.3 volts and the idiot light came on (I think the lower threshold must be around 12.3 volts because that's about where it was when the light came on/off).

This morning again, things started out fine in the mid 13s, then after a certain point it dropped suddenly to below 12 (~11.8) again and pretty much never went up again.

So, I'm definitely looking at an UNDER-charging scenario as opposed to an OVER-charging one.

I'm beginning to suspect the drive belt as well, and come to think of it, my power steering has been feeling a little stiff the past few days too.

So what's the hypothesis here

- the belt is stretched as they all do, and the tensioner just ran out of room to take up the slack?

- should I suspect my tensioner as well?

- I read somewhere that some of these alts have a freewheel pulley on them
- does mine have the freewheel pulley? how do you tell?
- can you change this separately?

So here's the story:

The car died and stranded my traffic, which made for a bit of a hectic day yesterday :)

Once I got it home I changed the belt - and after inspecting it I could tell the old one did dearly need to be changed - but it didn't fix the problem at all.

Either the alt itself or the voltage regulator is gone. I got my hands on one from the local guy I spoke of earlier who had one stripped off another car, but it's an aftermarket one (the OEM one was still on the block and I needed it right away... I may go back and get IT as a spare now :) we'll see...) but it seems to have done the trick.

I had hoped I could manage doing the swap without taking the power steering pump off, but I don't think it's possible. I took it off anyway. I guess it took about 3 hours to get the old stuff out and put the replacement in. Putting it back together was much faster once I learned where all the bolts/nuts were and how to reach them.

Anyway I think I'm out of the woods on this one and I'd like to thank everyone for their help and advice.

As it turns out I wasn't quite out of the woods....

The aftermarket alt I put in (as I said, it came off a '94 850 donor) died about 3 days later.

I decided I'd had enough fooling around, so I took the day off work and took the original OEM alt ( call it ALT-A) and the aftermarket one (ALT-B) to a starter and alt repair place to have them fully tested and find out what the hell was going on.

ALT-A had been pretty much ruined due to oil ingestion from this incident: http://www.brickboard.com/AWD/volvo/1332188/V70/oil_leak_2_help_cam_seal.html

Oil is apparently very bad for your alt and regulator.

The guy said he could rebuild the rotor, but he would need to order the regulator from Montreal and it would take ~5 days to get it. Cost ~$180 + time waiting for parts.

ALT-B had burned its regulator out. (The regulators on the two alts were different, BTW, so I guess you can't always 'mix and match') The guy told me the original regulator was of very poor quality, and he had in stock a replacement part that was made by Bosch. He could rebuild that one for me that afternoon, and the rest of the unit appeared to be in pretty good shape, though not of as good quality as the OEM Bosch unit. Cost ~$85.

I had him replace the regulator in ALT-B and it has been working fine since then.

The alternator does not have a free wheel pulley.

If the tensioner goes bad, you will be able to move it by hand rather than a ratchet. The belt will start to show signs of cracking when it goes bad. Check the rollers when the belt is off, they should spin freely and not wobble.

Signs also point to the brushes being worn out, buy the OEM from the local guy at least as a back up depending on the miles. Over 180K would be a little much, but then you could take off the voltage regulator and check the brushes and clean it up a little.
--
My name is Klaus and I am a V ♂ lv ♂ holic.

Thanks for the great advice KlausC. You're in your usual fine form.

I will be changing the belt tonight, and I'll be picking up the OEM alt as soon as I get a chance.

In the mean time I turned off my DRL and have hooked up a cheap solar charger (already had it) to help keep the drain on the battery mitigated. Now if only it were sunny....

I'll post back on the results of changing these parts to fill out this forum thread.

"Bud" is correct about the Sbelt slipping, check it for wear. Also check the red side of the battery post, it just might be loose, and the torque pulled the engine away just enough to give you a warning.
There is a voltage regulator bolted on the rear of the alternator which contains the brushes, but replacement cost is the same as an alternator - go figure. The brushes themselves are not replaceable.

Please check the wires, there is one that goes to the starter. If that comes loose, all sorts of things light up.

Don't ignore the warning light, it might come back to haunt you. But try the full throttle thing again and see if you can make it happen at will.
--
My name is Klaus and I am a V ♂ lv ♂ holic.

Thanks for the helpful advice KlausC.

I had no intention of ignoring the warning light :)

The 'warning light' aspect of all this turned out to be a good drill - my wife was with me in the car when the light first came on, and I said "Honey my charging system light just came on..." and she said right away as if reciting from a manual "if it's red pull over immediately and call your husband, if it's orange it's probably okay for a few miles but either get it home or get some advice ASAP." - I was very proud.

Altenator belt not properly adjusted??? May slip under full throttle until you let up???

Altenator belt not properly adjusted??? May slip under full throttle until you let up???