I'm wondering if anyone can shed some light on this one since I can't find
any similar problems via google...

My wife started complaining that she was hearing noises whenever she made a
left turn. I took the car out and tried to re-create the problem and
couldn't but I did get a very odd noise when I turned on the heater to
defrost the windshield. All I can describe it as is a kind of
rattling/revving noise that went on for about ten seconds then stopped. I
defrosted the windshield, then switched over to the main vents and cranked
the heat. The heat was working fine.

The last time something like this happened it was the AC compressor that had
died but that was only about five months ago and it was a very different
noise (almost a squealing noise) with the accompanying failure of the AC
system and a metallic smell coming from the vicinity of the compressor. I
turned on the AC and it got VERY cold very fast. I left the van running, got
out and leaned in close to the compressor. No smell. What could cause that
noise?