Tapping noise from back left area

[gsj87]

Hi all,
When I drove the X5 this morning to work, I noticed a tapping noise coming from the back left area of the car. I initially thought that it was something on the tyre and was only making a sound as the tyre went round and round.
However, when I came to a complete stop, I could still here the constant tapping noise every 2 or 3 seconds.
Any idea what this could be?

[Horizon]

If the temperature was less than 5 degs C it could have been the Webasco auxiliary heater, but that's usually a sound tapping clicking sound from under the passenger door well. Did it do it later in the day when things warmed up?

[X5Sport]

Webasto would be my suggestion too.  Heats the block and car up faster with a little diesel electric water heater.  Exhaust is just under the front passenger seat (under the car!).  Makes a gentle tick......tick.....tick when running.  Puzzles a lot of new owners that one 

[gsj87]

[quote="Horizon"]
If the temperature was less than 5 degs C it could have been the Webasco auxiliary heater, but that's usually a sound tapping clicking sound from under the passenger door well. Did it do it later in the day when things warmed up?
[/quote]

Sounds like that may be the culprit, once the car warmed up, I didn't hear a sound at all.
Is that a usual 'to be expected' sound then?

[X5Sport]

It is.  The Webasto kicks in whenever the air temp is <5°C