V70XC sounds like high revving electrical motor revving behind dash

[elmhome]

1998 V70XC sounds like high revving electrical motor revving behind dash, perhaps triggered intermittently by 50+mph speed. ??? Thanks.

[scot850]

Where behind the dashboard? High, low. Left, right? Does it only happen when driving?

Neil

[elmhome]

Thank you for replying. Only while driving, seems to be triggered by higher revs/speed (~50 mph) but occasionally buzzes in low speed traffic. First time was a real hoot. Seems to be in upper part--not sure left or right, perhaps more likely left--of instrument cluster.

[dikidera]

I do not know if it is helpful, but I've noticed that I also have a slight buzzing coming from..the instrument cluster. It seems to be triggered when you rev it and quickly let go of the gas, as the needles go down, there is a particular noise as they do so. Not always, but quite frequent.

[jdell]

Do you have the R style (xenon) headlights? I have the same noise and it’s something in the headlights for mine.

[scot850]

Can't think of anything om that side of the cluster that has moving parts on a 98 V70 XC. Closest thing is the cabin temp sensor in the middle of the dash just behind the little grille to the left of the ECC unit. They get plugged up with crap and can make them noisy. Then there would be your cabin fan but that is on the RHS behind the dash. When they get worn or the bearing dry, they can make different noises depending on seed and accelerating or slowing down.

I would check under the car and see if the heat shield over the propshaft has not broken loose and rubbing on it.

Then thee is the carrier bearing on the RH axle which get noisy as they fail. Hard to check without removing the RH axle. You could jack the front wheels off the ground. With the rear wheels chocked, but the trans in neutral (N) put the key in the ignition, turn to posn I or II, put your foot on the brake and press the small button to the right of the gearshift and move it into neutral. Then climb under the car and put one hand on the carrier bearing and use the other to spin the RH axle and feel for roughness/vibration in the bearing.

Neil.

[BEJinFbk]

If it's speed related, it could be air noise in the ducts.
Just for grins, try opening and closing the fresh air vents
in the top center of the dash when the noise is occurring.
.

98 x70 Air Mix Controls.png (145.58 KiB) Viewed 1347 times

[jsrnsis]

I had a very similar sounding problem that seemed to be some type of interference through the car speakers. I noticed it got a lot worse when I had installed an aftermarket bluetooth adapter that didn't properly connect to the CD changer port. It sounded like very high revving ball bearing noise that varied with engine RPM.
That and the little fan for the climate control in the dash sounds like a constant buzz in my v70.

[scot850]

jsrnsis, remove the radio, the ECC unit and then remove the cabin temp sensor/fan unit. Don't lose the foam seal on the front of it!

Clean the fan out and use a small amount of silicon oil on the bearing end and re-install. It should run quite.

Neil.

[elmhome]

Thanks, folks! Been laid up, will report back when this round is over.