Ac kicking on for no reason?

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Subiedude89
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Ac kicking on for no reason?

Post by Subiedude89 »

So my AC clutch keeps engaging for no reason the AC switch in the car seems to be working ok. I've noticed a lot of condensation and slight hiss coming near the heater core. Also found what looks to be oil at the switch near the passenger strut tower... What in the world is going on!?
w.rohr
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Re: Ac kicking on for no reason?

Post by w.rohr »

In my limited technical ability it sounds like a switch issue perhaps the insulation is off a wire somewhere and its shorting out. That happened to my backup lights once.
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anarchy1024
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Re: Ac kicking on for no reason?

Post by anarchy1024 »

Just to confirm, the air flow direction switch isn't in either of the two windshield settings, right? The defogger uses the AC compressor to remove moisture from the air before blowing it against the windshield.
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Guacamole
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Re: Ac kicking on for no reason?

Post by Guacamole »

Is the compressor turning on even when the AC is off, the blower dial NOT set to either defrost & feet or defrost, and the interior fan dial is turned off?
My compressor cycles with the fans every 20-or so seconds with the AC off & I figured it was just normal as it looks like the compressor is also linked in with the radiator fans, figured this is just by design.
F.Y.I the AC discharge is right next to the passenger front strut.
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anarchy1024
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Re: Ac kicking on for no reason?

Post by anarchy1024 »

If the AC switch is off, the blower dial NOT set to either defrost & feet or defrost, and the interior fan dial is turned off, my A/C compressor doesn't cycle. The A/C compressor cycling is only linked to the cooling fans cycling when it's turned on (A/C switch or defrost), and at that time, both fans come on. Normal engine cooling appears to only use one fan.
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kamesama980
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Re: Ac kicking on for no reason?

Post by kamesama980 »

To explain the other way:
Standard procedure for darn near all cars is to run the AC when the defroster is used. Some manufacturers also use it when the lower (foot) vents are selected. My wife's Mazda was like this: the only time the AC wasn't automatically engaged was dash-vents only.

If the above doesn't apply, it's likely the HVAC control computer. The button may appear to work but the wiring to the computer may be shorted sending a false AC-request = true message (thinks the button's pressed). Failure of the AC system pressure sensor or wiring can prevent the AC from turning on (reports the pressure is too low or too high or sensor disconnected), but cannot cause it to turn on. Electrical faults after the HVAC computer (IE shorting the clutch wiring to turn it on) won't cause it to cycle.

The residue/leaks are a totally separate and unrelated issue that are just that: Leaks.
-Russell
"You don't get to judge me for how I fix what you break"
03 sport 5mt
05 turbo 5mt vf39 and other STI bits, 3" turbo-back
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