Lights dim with power steering

[HeavyHanded]

Hello everyone, I am the new owner of a 2011 xc70 with 123k miles. I just picked it up today and was sitting in it setting up my phone, when I turned the wheel and noticed the lights dimmed pretty significantly. Every time I turned the wheel a bit the headlights and cabin lights would dim. The dealer said it has a new battery. Could this be a problem with the alternator or power steering pump, or totally normal? It was about 30 degrees F outside if that matters. Thank you!

[pbierre]

So, you weren't rolling, just sitting parked. Was the engine running? Does the same thing happen when driving?

Is this an intermittent problem...or something you can replicate at will?

To see if this is a system-wide undervoltage condition, you could observe the effect on the windshield wiper motion, power window motors, or seat adjustment motors. If the engine is running, and every motor slows down and every light dims in response to the steering wheel turn, that would point to a systemic undervoltage.

If the lights are dimming when the engine is turned off, then that would suggest a problem in the steering wheel housing....the steering angle sensor, or a short in the wiring paths for the control buttons (stereo volume, cruise control, etc), or the security system immobilizer.

Do you have a voltmeter you could slap on the battery to watch? Or, do you have an OBD-II scanner device -- it will give you the system voltage
reading second by second.

Were there any diagnostic faults showing on the console?

[HeavyHanded]

I was sitting in park with the engine running. Lights dim every time the wheel is turned, and the power seats seems to lag down while moving them and wheel is turned. It does not appear to do it while moving although I will have to wait until it is dark to more easily tell. I am going to go pick up a voltage meter now and will post my findings. I do not have a scanner.

[HeavyHanded]

I was not able to get a voltage meter, I will have to get one tomorrow. The lights only appear to dim when the car is parked and idling below 1k. If I rev the engine a bit I can turn the wheel without dimming.

[pbierre]

Here's 2 other conditions to be tried, they could yield a clue:

Ignition position 1. Put key fob into slot. (Press start button WITHOUT foot on brake pedal) Engine is off, accessories turned on.
Are you seeing dimming of cabin lights with steering wheel rotation?

Ignition position 2. Put key fob into slot. (Hold in start button 2 seconds WITHOUT foot on brake pedal) Engine is off, accessories turned on,
plus fuel pump, ignition coils, all head and tail lights
Are you seeing dimming of headlights with steering wheel rotation?

With the engine running, it seems that the idle engine speed driving the alternator is not producing enough current to overcome the
current drain of whatever the problem is. But with higher RPMs to the alternator, the deficit is made up. We're looking then for a short-circuit
or current over-draw (such as happens when an electric motor is turned on but stalled). It's not enough to blow a fuse. (That might help locate the problem circuit, as the fuse would be heating up much more than it should be.) But, 1st things first...check the other 2 ignition switch conditions.

[HeavyHanded]

I do not detect dimming in position 1 or 2, only when engine is running and idling under 1000 rpm

[pbierre]

OK, more good clues.

The steering system is still the focus. Do you have a pair of jack stands? I'm thinking to raise the front end enough to get two front tires off the ground,
then there'll be much less resistance to turning front wheels. If this lessens the electrical drain, then it's narrowed down to the power-assisted steering system.

The other tack might be to try to get a fuse to blow (the circuit drawing too much power). Here's the approach. Get another car, and attach jumper cables.
This will double the available power during the steering-wheel "brownout". Open the engine fuse compartment behind the air filter, so you can see and touch fuses.
Now, trigger the brownout condition for a good minute duration. If this doesn't blow the fuse, it should be getting hot. Do you have a digital cooking thermometer?
Touch each fuse (the metal conductor), and hopefully one will be hotter. If that works, I'll get you to the fuse chart for the 2011.

[HeavyHanded]

I still get he brownout with the front end lifted. I connected the battery to a booster car and turned he wheel back and for for a minute, all the fuses seemed to be no warmer than 60 degrees according to my instant read thermometer. It’s hard to tell in the daylight but it seemed the brownout occurred even with the booster battery attached.

[pbierre]

The steering system on these P3 Volvos is a servo-controlled steering column driving a pinion rack with hydraulic amplification. There's no electrical parts on the rack & pinion, nor on the power-steering pump and fluidics.

The servo-controlled steering column consists of the following. There's no direct mechanical linkage of the steering wheel to the shaft that drives the rack. Rather, there's a Steering Angle Sensor inside the Steering Wheel Housing that measures the angle you are turning the steering wheel.
This value goes to the Steering computer, and that value is passed along to the motor actuator that does the turning of the shaft. This motor is likely starting to fail, and drawing way too much current. I think to prove this, it's a matter of temporarily taking out fuse #44 (engine compartment Bank A -- Electro-Hydraulic Power Steering), and see if the brownout goes away. Let us know your results....this problem is fairly unique.

One of the clues that your Volvo has a servo-controlled steering drive shaft is that the software preferences allow you to set the turning sensitivity of the steering wheel.

[HeavyHanded]

Thank you for the replies. I brought the car back to the dealership and I will relay this information to their techs.