Zafira engine strange noise every 15 seconds ??

[gr1340]

Just been to look at a 2005 55 plate Zafira 1.8 petrol. Drove fine but on tickover, every 15 seconds or so, the revs would drop slightly, a grinding/whirring noise would start for a second then it was ok again. It kept doing this even when it was warm.
Car had 70k on it and cambelt would be due later this year.

Any ideas?

[miniman]

Possibly faulty A/C compressor trying to kick in and failing?

[gr1340]

Ac wasn't on at the time though which I assume wouldn't cause it

[littleredrooster]

If it has 'intelligent' charging, it could be the alternator coming under load to charge the battery.

[gr1340]

Intelligent charging sounds plausible. Surely someone must have a Zafira B petrol that can confirm this?

[Rickyy]

In some Fords, even with the AC turned off at the button, it will actually be on if the demisters are in the windscreen position and the fan is turned on.

Could be the same with Vauxhall?

Either that or the radiator fan is playing up and running continuously.

[gr1340]

Rad fan wasn't on and doubt it was hot enough. I may have put the air flow switch to window and face but didn't turn air con on but that also sounds plausable.