I have a 2006 S40, that is having some severe electrical problems. These problems seem to occur when the car has been driven for a minimum if 20 min. The same sequence of problems occurs each time the car is driven over 20 min. The first thing that happens is the headlights lights brightness seems to fluctuate and the radio cuts in and out.
Then their is a message on the cluster that says urgent alternator system repair with the battery symbol illuminated. Then after a few more minutes I get an ABS light in the cluster the Power steering stops working and the car dies and cannot be started or driven. But after about 20 min the car can be started and driven a shot distance. after leaving the car overnight the car will run great until the 20 min mark when it all starts again.

I have taken it in to our local dealership, they seem to be stumped, they replaced the CEM ($1000), which had no effect.

Please help as I cannot afford to sink more $ into this car

 

Sure sounds like a generic alternator failure. Yes, it could be something that feeds / controls the alternator, but alternators DO wear out and DO fail, while electronics tend to not be the problem. I hope you were able to recover the $1000 for the non-repair - yikes! This shouldn't really be a tough problem for a good shop to fix, if it's repeating consistently, maybe you could pull into the shop while the car is misbehaving so they can take a couple simple (read "cheap") measurements which will tell them definitively whether it's the alternator, or something else (wiring / connector / battery / computer).

 

OK Thanks, I just thought the alternator was fine because it seems to be charging fine, and the battery hasn't lost a step. But, I guess it could be a communication error between the computer and the alternator.

I do have an OBD2 scanner and it doesn't tell me anything.

Thanks, I will try to take it in when the problems are occurring, the only problem is I live about 45 min from the dealership.

 

Life is a lot easier if you have a voltmeter (and know the basics about how to use it). That way, you could just check the voltage at the battery and see if the alternator is putting out close to 14 volts. If it isn't, it's a bit more complicated to check out if the voltage sensing circuit is working right (or not).

Voltmeters can be had dirt cheap from Harbor Freight (for example), and in fact, they often run a special where you can get a free voltmeter (you need a coupon - just keep your eyes open for one). They're not great meters, but are great to keep in the glovebox or trunk for an emergency.

Barring that, there are small cigarette lighter plug-in voltmeters that can be had for a few bucks, and would let you keep an eye on the charging system real-time (so you'd have more notice when it was going south). Here's the cheapest amazon meter I found in a very quick search (not endorsing this particular one, but it should be adequate for your needs)…

 

so, here is an update, I did not drive the car because it has been unreliable and I was waiting to get the cigarette lighter volt meter from Amazon. It has now come and I have some more information, for the first 15 min. of the ride the voltmeter reads anywhere from 14.8-15.2 volts (seems a little high). Then after 15min. the volts drop to about 12 and eventually lower about 11 then the dash lights come on about the alternator. while this is occurring the headlights seem to become dim as the volts drop and the radio intermittently cuts in and out.

this seems to me to be a problem with the Regulator, thoughts...

 

I agree with your assessment. Almost certainly a voltage regulator (or general alternator) issue. If it was a "loose wire" somewhere, chances are that it wouldn't be related to heat, or take 15 minutes to show up.

It's still theoretically possible that there's a loose connection somewhere that's NOT in the alternator, but if it was my vehicle, I'd just swap out the alternator.

Those cig plug voltage monitors are pretty cool, huh? ;-)

 

+1 on the Voltage regulator. Sounds like one of the diodes warms up then open circuits and you start running off the battery. When that drains down below 12.5 volts, odd things start happening. I bet if you sprayed some cold on the regulator it'd come back to life. Does it go back to 14V after shutting off the engine and restarting? Note on some alternators you can replace the regulator and keep the rest of the altnerator. Not sure if that's an option for the 06.

 

Ok great thanks for the help, I will keep you posted. thanks again

 

Hey guys, sorry for all of the questions. Can I just replace the Voltage regulator or do I have to replace the entire alternator?

 

Good question. I guess I'd be less likely to try that unless I was able to conclusively prove to myself that the problem WAS "just" the voltage regulator. In your case, this may well be possible by idling the car until you have the problem (or driving it, then pulling over) and then monitoring the output voltage of the regulator (aka "battery voltage") while you spray the voltage regulator (the part that the plastic connector plugs into on your alternator) with a cooling spray of some sort. If the voltage immediately returns to "full charge", you will know that you probably CAN get away with replacing just the VR.

OTOH, there could be other failures that are causing the problem, internal to the alternator (intermittent diode, connections, brushes, etc.). If so, you'll spend quite a bit of money and time swapping out the VR for nothing. And let's face it, if your alternator has a boatload of miles on it, it might not make sense to put TOO much money into fixing the alternator instead of replacing it with a new or remanufactured unit (assuming it was reman'd by a good vendor, of course).

 

If you can find a supplier I would love to know it. It's not that you can't replace the voltage regulator, it's just that no one sells it to the public. I found a local shop that does alternator rebuilding and had them use the better quality parts.