Underhood whine with engine off

**MoeMan** · 09-14-2009, 05:08 AM

My wife drives a 2008 XC70 with 20,000 miles on it. This morning I took some things out to the car (didn't do anything except open the door, drop her stuff, and closed it). After closing the door, I noticed a high-pitched whine coming from underhood. I opened the hood to see if I could identify the source, but didn't have much time. I only was able to note the general area which was driver's side, definitely seemed to be either something bolted to the engine or very close to it. I started the engine and turned it off, and still the whine persisted. I had to leave for work so that's as far as I got.

Has anyone had a similar experience or know what this could be?

**Forkster** · 09-14-2009, 08:41 AM

It's a fan either for your air conditioner or radiator. If your engine is hot, or if its hot outside, either fan (or both) will run for around 10-15 minutes after you turn off your engine.

**modoimage** · 09-22-2009, 11:10 AM

When I first got my XC70, I've noticed that whine too. At first, I thought it was the rad fan, but still it seemed that it was too quiet for the fan motor.

Then I've asked a tech @ my local dealer on the issue, then he explained to me that it is the turbo timer in the system.

He also said that it doesn't come on often, with the exception that you've been on the hwy at high speeds.

Hope this helps.

**Matters** · 10-31-2009, 06:31 AM

Mine does this too. I don't have a turbo. I think it is associated with the electrical system. Doesn't seem to be problematic.

**waldi** · 11-26-2009, 11:34 AM

I believe it is related to AC use, system vents AC ducts after use.

**beavenx5** · 11-26-2009, 02:52 PM

Same thing on my XC70 T6. I hear it quite often in the garage.
My old car (2004 Mercedes C240) used to do a very similar whine almost every day so when I heard it for the first time on the Volvo I was not worried.

Definately not a noise from the cooling fan. Most likely electrical. I don't think it is from the A/C as it does it in the winter also when the A/C rarely works.

Last night I also heard a funny noice from the rear of the car. I beleive it was from a hydrolic pump in the rear suspension. It lasted about 1 minute and then stopped. First time I hear that one...

**Lotus99** · 11-26-2009, 07:34 PM

Originally Posted by beavenx5

I don't think it is from the A/C as it does it in the winter also when the A/C rarely works.

Au contraire, mon frere...

We leave ours in the auto position, and it probably works quite a bit I'd say in the winter actually, because it's so wet and humid out. The A/C in fact will come on automatically if you press the windshield defrost button (even if the A/C is off), because that's the best way to defog the windows, not just by using heat, but by removing the moisture out of the air, which is what the air conditioner does besides cooling air. In fact, there's a humidity sensor in the interior rearview mirror for this purpose.

With most cars nowadays, even with the heat on, the A/C is on automatically, unless you disable it.

As the manual says: "The air conditioning can be switched off, but to ensure the best possible climate comfort in the passenger compartment and to prevent the windows from misting, it should always be on."