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Re: Air-con clutch going bad?

The AC compressor has an electric clutch that connects the pulley, which always turns when the motor is running, to the compressor. Check if this is available separately from Subaru. When you bring the car to them, have them listen to the noise, since the car will be warm at that point (put AC on, fan at full speed to cycle the AC more quickly. It might make less noise at idling speed, though, since the motor is turning slowly, but you can push the throttle or step on the gas to increase the speed).

Hi all, > for a while I've been noticing a strange noise (somewhere between > grind and rattle) whenever the air conditioner engages or > disengages. Now, at 100000km it is becoming really pronounced. > > I suppose the air-con is hooked up via some sort of clutch, and > I've been theorizing that this clutch may have started slipping. > Has anyone else ever noticed that? Is it something a scheduled > service should be able to fix (the 100000km is coming up)? I'm > not sure how to explain the problem to them. It only occurs after > the car (and air-con) have been going for a little while, and > service staff don't usually take the time to run the car for a > while. > > This is on a '00 Outback wagon, btw. > > Cheers > Steffen. >
Reply to
ed
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According to ed :

That's good advice, thanks.

In fact, I only ever noticed the noise while the engine was idling (usually when I got out of the car to open the garage door).

Cheers Steffen.

Reply to
Steffen Kluge

Don't system pressures (and therefore compressor torque demands) go up at idle (since the system will try to deliver the same BTU's but at lower speed)? Also, at higher rotational speeds, the clutch and compressor rotating parts act like a flywheel, so the belt is less likely to slip to carry the compressor thru the pulse torque loading that it sees.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

Reply to
Bill Putney

Reply to
Edward Hayes

Since you seem to have hands-on experience with this, I will defer to your experience. When I had an a.c. hose on my '86 GL-10 wagon burst a couple of years ago when it had been idling for a period of time, I was told that the hi-side hose pressure goes up during extended idling.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

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Bill Putney

Reply to
Edward Hayes

Sounds good to me. Yes - I was referring to average head hi-side pressure.

What I was trying to say is that from a purely theoretical aspect, if the system is operating closed loop, at idle (because speed is lower), hi-side pressure should have to go up in an attempt to put out the same BTU's (since total energy output is related to the product of rotational speed and pressure, so if lower speed, pressure must go up; higher speed, pressure goes down in a closed loop system). I don't know if this translates into real world automotive a.c. design though. I know that I have heard auto a.c. mechanics say more than once that the system pressure (again, I assume that means hi-side head pressure) increases at idle (and, again, why my hose blew out at idle rather than at highway speed).

I only mentioned the pulses as an additional effect on belt slippage in relation to lower compressor speed translating into less flywheel effect from the clutch and rotating parts of the compressor, and therefore more tendency of the belt to slip at low speeds from that (pulsing) effect.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

Edward Hayes wrote:

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Bill Putney

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Edward Hayes

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