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2005 Outback LTD 2.5l 4EAT
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Discussion Starter #1
i was waiting outside a friends house today. the ac was on, outside temp was about 100 deg. F. after a few minutes the engine seemed to start running rough. i turned the ac off and it ran fine. i opened the hood and found a rats nest on top of the engine!! i threw away the big stuff and vacuumed it all out when i got home. the only damage i found was one small wire chewed through but it was for the remote start. i spliced it back together. anyway, i noticed the ac clutch was not cycling. i don't think i've ever seen it stay engaged more than 15 seconds since I've owned the car! today i timed it for 3 minutes before i turned it off. and now to make things more interesting... on the highway or if i rev the engine up to 2500, it cycles fine.
 

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Check the electrical system voltage, the voltage to the compressor clutch, and the clutch gap.

The compressor clutch is engaged by an electromagnet. If the electrical system voltage, or the voltage to the electromagnet is too low, not enough current will flow through the electromagnet, and the clutch will not be engaged (pulled in), or if it is engaged, it might not hold. There's a two wire connector on top of the compressor. One wire goes to ground. The other is the power for the electromagnet. When the AC is supposed to be running, there should be at least 10.7 V at that wire (with the connector attached to the compressor and the wire back-probed for measurement). If there was signs of the wires being chewed, ensure that the wires to the electromagnet haven't also been damaged.

Bad/worn contacts in the AC Relay in the engine compartment fuse box could be a cause of low, or no, current to the electromagnet. It's not uncommon.

Also, the gap between the clutch drive plate and the pulley can increase over time due to wear. If it's too large, the electromagnet might not be able to pull the flexible plate tightly against the rotating pulley, all the more so when the supply voltage is low, which is more likely at idle and lower engine speeds. Gap spec is 0.45 +/- 0.15 mm (0.0177 +/- 0.0059 in).

How long have you had the car? Has the AC refrigerant charge ever been checked (using proper AC manifold gauges)? Regular cycling at 15 second intervals doesn't seem right. Rapid cycling of the compressor due to incorrect charge could lead to excessive wear on the clutch and on the relay switching contacts.
 

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2005 Outback LTD 2.5l 4EAT
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Discussion Starter #3
thank you for your reply!! there's a lot of good info there! however, I feel you did not understand the problem. the clutch stays engaged at idle. ie the compressor runs continuously.

i did check ac pressures with gauges last year. i will be doing it again.

regarding the "normal" cycling rate of 15 seconds; how long does your compressor run? everyone I've talked to says cycling of 10-20 seconds is normal for this era Subaru.
 

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My misunderstanding.

Most related issues raised here would be about constant cycling; I don't think I've seen a post concerned with the compressor running continuously when the fan and AC are turned on. However, on re-reading your first post, I see that being the issue.

I'm not all that familiar with the HVAC in the Limited, which is automatically controlled. That introduces additional factors that perhaps could have caused the sudden change in apparent operation.

Sure there's no other wires damaged by the visitors?
 
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