Volvo S40 battery dying and whizzing sounds

Check for a bad harmonic damper at the crank pulley if equipped. The alternator could be loosing charging capacity.

Based on your observations, the loss of power steering suggests a belt problem. Couple that with an unusual noise and I'd be looking at the vibration damper. Many of them have the outer ring with the pulley cast into it. That ring is glued to the hub. Very often that gel lets go and the ring falls off. It can spin too. The trick is to catch it while it's acting up so you can see if the belt is turning slowly. Auto parts stores have catalogs full of replacement vibration dampers.

Also check the belt tension. If the spring-loaded tensioner pulley is weak, the belt will slip but it will usually make a horrendous squealing noise too.

There's no relay and nothing electrical related to the intermittent loss of power steering. That has to be belt-related.

As far as "will it solve the problem?" That depends on the cause. You haven't positively identified that yet. All we can do is guess based on the information you provided. KHLow2008 came up with the same diagnosis based on reading your same observations, but you still don't want to randomly throw parts at a problem until you know for sure we're right or wrong. Very often we're wrong, and we find that out after the owner investigates further the things we suggest. Many of the causes are impossible to think of without actually standing by the car and seeing what's going on.

The power steering pump uses an electric pump controlled by the power steering module and the throttle has no cable so it is uses info from the pedal and other sensors to open up the throttle. So a faulty alternator not charging would cause very low battery voltage where the pump and throttle will not respond. The voltage regulators go bad on this alternators or the alternator itself could be failling? The central electronic module will also post several codes one will be EPS-71 for low voltage to the power steering. Low voltage will also set the SRS light, cause the climate damper motors to lose calibration, windows auto up function to lose memory, and a bunch of other crazy faults. With the miles you have I would recommend you just replace the alternator since the voltage regulator comes with it. You can also remove the voltage regulator off the alternator and inspect the brushes for wear but sometimes you replace that and a month later the alternator goes bad internally? So I recommend the alternator replacement.

Thanks JIS001. I really hate all this use of unnecessary, over-complicated technology and it's why I'm sticking with my rusty trusty '88 Grand Caravan. I have power steering and brakes, power locks, power seats, power windows and mirrors, ... And no computers involved. Sure wish someone would build a new car like that.

LOL I thought I was bad putting on band aids on my wifes 1995 Windstar. Just went over 200k miles.

Thanks for keeping us posted lamrques. The alternator should take care of your problem. If you installed an aftermarket alternator and problems return again then you will need to get the alternator from the dealership. Sometimes the aftermarket ones work and sometimes they dont? Good luck to you.