I’ve started exploring the damage to my new Cat C today and although I had no power as the main fuse/relay box was damaged in the accident I took the broken casing off and pushed all the relays home and then bench charged the battery overnight.

I now have power but the fuel cut off has activated which is quite usual. I often have trouble reactivating it using the turn key to MAR Etc etc but when I turn on the ignition I have a strange electrical whirring noise which seems like it’s coming from under the dash sort of behind the stereo.

I’ve recorded it in the attached video. Any ideas what that could be? It’s mot the heater fan or stereo.

I’m hoping MES can also reset the fuel cut off.

[ame]https://youtu.be/XtdkDq34HHs[/ame]

What type of temp control, dials or climate control? Though it's not unlike the screen washer pump sound? Does the sound continue if left have you listened under the bonnet whilst it's making the noise?

Sounds rather like my fuel pump does when priming perhaps try disconnecting the fuse for it see if you still get the noise

Or do you mean the constant buzzing noise?
Sounds like the fan but I'm assuming you have turned that off?

When it stops on the clip, that’s when it stops. It’s manual A/C but is switched off. I haven’t listened under the bonnet as the car doesn’t have a bonnet!! It’s a really weird noise, definitely an electric motor of some kind. I wonder as the fuel cut off is activated it’s something to do with that. I’m going to plug MES into it tomorrow to see if that tells me anything.

My first impression was the drive motor or loader motor in the CD with damage or a stuck disc but you've said it's not the stereo.

[ame]https://youtu.be/Skq5GFXP6yY[/ame]

Does this sound like the same noise to you?

This is from my 09 500 the sound comes from around the fuel filter area so I've always assumed to be the fuel pump

Piccolo Nero e Bella said:

My first impression was the drive motor or loader motor in the CD with damage or a stuck disc but you've said it's not the stereo.

Click to expand...

That's what I thought first, and to be honest that's what it sounds like but it's switched off.

Sounds like the HVAC sampling fan is noisy.

Goudrons said:

Sounds like the HVAC sampling fan is noisy.

Click to expand...

The what?

chris3234 said:

https://youtu.be/Skq5GFXP6yY



Does this sound like the same noise to you?



This is from my 09 500 the sound comes from around the fuel filter area so I've always assumed to be the fuel pump

Click to expand...

It does sound very similar to that although much louder. If it is the fuel pump, I wonder if it’s noisy as no fuel is reaching it because the cut off has activated. Due to the weather today I didn’t get round to doing anything today. I need to reactivate the fuel cut off.

Fingers crossed that gets rid of it.

I’ll let you know. Cheers.

Bear in mind my car has a fully intact bonnet and it's also closed haha
So that could likely dampen the sound as my phone may not pick sound up as well as yours



But the sound defenitly seems to come from around the fuel filter area

chris3234 said:

The what?

Click to expand...

HVAC is the heating, ventilation and air conditioning system.

In the dash, behind that small grill, just below the heating controls in a small fan.

It draws in the air from the cabin so it can sample the cabins temperature and work out what it needs to do to match the requested setting.

They often start up just after the ignition is turned on and run for a minute or so.

After a while, dirty and dust get drawn through the little grill and builds up on the fan blades causing the motor to get noisy.

Most of us have heard similar noises from the back of our PC's.
The cooling fan in the power supply units gets full of dust and rattles away.


It's a very common issue, a quick search of Youtube will return lot's similar videos.

Yes, we had an A-Class that used to make a very faint noise from the a/c after the engine was switched off - it stopped after a couple of minutes. However, although it didn't have full climate control, the temperature was thermostatically controlled, which meant the little fan sampled the air temperature.
Does the basic a/c on the 500 have such a system? I suppose it could as the grill is there, or is that moulded piece common to the versions with climate control?

I donr think the system of the 500 is that advanced
Not unless you go for the full climate control package

Disconnect the radio, not just switched off, and see?

John202020 said:

Disconnect the radio, not just switched off, and see?

Click to expand...

I think I’ll try putting an old cd in and see what happens.

I plugged in MES this morning, did a reactivation of the fuel pump and the noise has stopped so it must have been the pump trying to prime. Never heard that before but the car has now started for the first time since July. [emoji15]

What engine is this a diesel? If so there pumps do run at a higher pressure

No 1.2 petrol.