06 avensis idle is linked to heater fan switch !!!!?

JMSE

The following is true when the car hasn't yet reached normal running temp: When I stop for any reason such as a red light or crossing swans, the idle increases.

So as this has been ongoing now for a few months, this morning I happened to notice that it only happens........when the heater fan is switched on. There I am at Confey Bridge in Leixlip (stopped at red light) and I knock the fan off and whaddya know - the idle drops to normal.

So am wondering if anyone out there has a theory.....................

corglass

You most likely have your AC turned on. The AC pump has a mechanical load that the engine compensates for by increasing its rpm and increasing its idle hp output.

If the fan is left on, but the AC turned off, you'll still get your heat output but there'll be a reduced engine load so the engine RPM will drop back to its 'normal' level.

You'll use less fuel too

visual

JMSE wrote: »

The following is true when the car hasn't yet reached normal running temp: When I stop for any reason such as a red light or crossing swans, the idle increases.

So as this has been ongoing now for a few months, this morning I happened to notice that it only happens........when the heater fan is switched on. There I am at Confey Bridge in Leixlip (stopped at red light) and I knock the fan off and whaddya know - the idle drops to normal.

So am wondering if anyone out there has a theory.....................

No theory it's a fact they all do this and yes it is they way it was designed from new.

colm_mcm

I know my TD avensis had this as a feature, it was to help the engine warm up quicker, wasn't dependant on AC.

Truckermal

colm_mcm wrote: »

I know my TD avensis had this as a feature, it was to help the engine warm up quicker, wasn't dependant on AC.

Lol I still love it and that feature! !

colm_mcm

Off topic, but you still have it? saw you selling it a few months ago

Are you replacing it with the passat?

Truckermal

colm_mcm wrote: »

Off topic, but you still have it? saw you selling it a few months ago

Are you replacing it with the passat?

I still have it but I think I'll keep it as it's a great car, no the new Passat is for the wife..

JMSE

Thanks for all the shtuff above everyone!!

My theory was that my battery must be fading, and that the alternator was under pressure to both recharge a bad battery and provide the power for the fan and so was boosting the revs, but the flaw with that was that the wipers and lights werent causing the same boost.

So its a feature to get the coolant up to temp quicker??!! Suppose that'd be frowned upon now with the emissions specs being so tight.

Chimaera

JMSE wrote: »

Thanks for all the shtuff above everyone!!

My theory was that my battery must be fading, and that the alternator was under pressure to both recharge a bad battery and provide the power for the fan and so was boosting the revs, but the flaw with that was that the wipers and lights werent causing the same boost.

So its a feature to get the coolant up to temp quicker??!! Suppose that'd be frowned upon now with the emissions specs being so tight.

No because the emissions are much worse on a cold engine.