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Solved - Idle with AC on too high

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My 84 wagon (EA81, electric dizzy) is idling fine at 800 RPM and was idling at 950 with AC on. It has just started running at 1200 rpm idle when the AC is on. I noticed that when I put AC both of the (factory) electric fans come on as well - would this increase RPM. I thought it would draw current and drop the RPM a little (ie when the thermoswitch trips the fans without the AC on the RPM drops about 50). What could cause this RPM increase - the relay?, switch, Electronic components in the dizzy? Help me, my wagon is mint and I want it good, it is a one owner (21 yrs) full subaru service history and only 120,000 kms (75K miles) - oh and it is 38 Celsius (100 F) and a balmy 42 (107 F) predicted tomorrow - good thing I got a brand new radiator from the JY for $16 - beauty.

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My 84 wagon (EA81, electric dizzy) is idling fine at 800 RPM and was idling at 950 with AC on. It has just started running at 1200 rpm idle when the AC is on. I noticed that when I put AC both of the (factory) electric fans come on as well - would this increase RPM. I thought it would draw current and drop the RPM a little (ie when the thermoswitch trips the fans without the AC on the RPM drops about 50). What could cause this RPM increase - the relay?, switch, Electronic components in the dizzy? Help me, my wagon is mint and I want it good, it is a one owner (21 yrs) full subaru service history and only 120,000 kms (75K miles) - oh and it is 38 Celsius (100 F) and a balmy 42 (107 F) predicted tomorrow - good thing I got a brand new radiator from the JY for $16 - beauty.

 

There is a vacuum thingy (FICD) that opens the throttle a little w/AC on.Set the AC idle speed by loosening the locknut and turning the adjustment screw w/AC on.

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Perhaps your AC clutch is not engaging. The AC idle-up would then make the idle too high as it is expecting to have to drive the compressor.

 

There should be an AC pressure switch that will not allow the compressor to engage unless the system is pressurized with the correct amount of refrigerant. Perhaps you have sprung a leak.

 

Both fans are supposed to come on with the AC - normal.

 

GD

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Solved - thankx USMB, subiemech, naru and as always GD. It was indeed the vacuum adjustment. I didnt mention I had just rebuilt carby after dirt in petrol Again!!! (Outback service stations) GRRR!! Must have gone on differently adjusted, all is good now. Learning something like this about my car is why I love these forums.

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