500rpm too low?

[chanham]

Hi all,

I purchased my car over the winter period, and now its beginning to become hotter I'm starting to use the air-con now.
only issue is there is in loud vibration noise when the ac is switched on, in drive, stationary and warmed up (at the lights for example).
Have never noticed it before (because i didnt use the ac for the first few months)

the sound it intermittently and not constant (maybe every 10-15 seconds)

thought it would be the ac compressor maybe, but I've noticed my car idles at around 500 rpm with ac on...which may be the reason for the vibration sounds.

is that too low?

[zch91]

It will be intermittent because of the AC clutch engaging/disengaging the compressor.. As to why it's causing you issues I couldn't comment. Rob will chime in sooner than later and tell you why.. He seems to be the AC guru around here!

[Dropz]

When AC cuts in it should idle about 800 rpm. AC off should be about 650-700rpm

[chanham]

hmmmm maybe my idle is too low...

[Dropz]

A dealer can raise it with the Subaru Select Monitor 3.

[Ric]

That's controlled by your ECU. It knows what RPM you are doing, and should open the DBW throttle enough to maintain the specified revs.
There's a definite problem if it can't.

[chanham]

im guessing subaru are going to charge me a stupid amount for that...if its ecu related, would new tune tell it what revs to idle at?


...no im not going to get a tune just for this, but i was planing to get one in the near future...might aswell bare with it alittle longer and put the cash towards the tune!

[zch91]

Tune is cheap, wait till KiDo is in WA next

[Dropz]

Raising the idle takes about 5 minutes. Doesn't require retune or any of that. Its a code programmed into the SSM3 and you can raise or lower the idle at 50 or 100RPM increments between 500 and 2000RPM (from memory)

[chanham]

would you constitute this as 500RPM? With AC on too...









It its ecu related, might just use this as another excuse to do the tune

[kleinerbastler]

You can adjust it by yourself with this little tiny software FreeSSM http://developer.berlios.de/projects/freessm/
it is an opensource version of the Subaru Select Monitor - very nice. You just need a simple obd2 usb cable from amazon or ebay for 10-15 bucks.

[alessandro132]

would you constitute this as 500RPM? With AC on too...

Mine idles around 700rpm with AC, without it's about the same really...

[Dropz]

That is about 700rpm. the little black line between you needle and 0 is 500rpm.

The reason 500rpm is closer to 0 than 1000 is because the car should never be below 500rpm.

[chanham]

ohhhhhhhhhhhhh! guess my ac compressor is fucked then.

[Robbks]

It may be an idle up, TPS, or throttle plate problem and not an AC problem>
try cleaning the throttle plate and housing first, it may be sticking