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PostPosted: Mon Jun 29, 2009 6:15 pm 
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Junior WRC

Joined: Tue May 23, 2006 8:06 pm
Posts: 595
Location: Knoxville, TN USA
Car Model: None
It affect idle some, but I feel a loss of power through the whole power band. Its almost like it runs in a safe mode when I unplug the ACT wire. If I knew what signal the ECU needed to see, I might be able to come up with a way too fool it.

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1992 Celica Gt4 RC Conv. St205 swap
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PostPosted: Wed May 25, 2011 9:58 pm 
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Junior WRC

Joined: Tue May 23, 2006 8:06 pm
Posts: 595
Location: Knoxville, TN USA
Car Model: None
I finally got the car back after all this time and plan on sorting out the AC. Anyone know the function of the act wire?

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PostPosted: Wed Jul 25, 2012 3:29 pm 
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Junior WRC

Joined: Fri Jan 29, 2010 10:39 pm
Posts: 514
Location: Bournemouth
Car Model: ST205
would this help ?

The engine ECU turns OFF the A/C compressor in accordance with vehicle conditions to maintain good drivability and acceleration performance. For example, when rapidly accelerating from a low engine speed, the engine ECU turns OFF the A/C compressor in accordance with the vehicle speed, engine speed, throttle valve position, and intake manifold pressure or intake air mass. There are two types of air conditioner control systems. One type indirectly controls the air conditioner operation via the A/C amplifier. The engine ECU sends an ACT signal to the A/C amplifier to disengage the magnetic clutch of the A/C compressor. In the other type, the engine ECU directly controls the air conditioner operation by operating the magnetic clutch relay. With some engine models, after the air conditioner switch is turned ON, the magnetic clutch operation is delayed for a moment. At this time, the engine ECU opens the ISC valve to increase the engine speed to prevent the engine speed from dropping when the air compressor operates. This delay control function is called air conditioner compressor delay control.
Cooling Fan Control
There are various types of cooling fan controls in addition to the one shown in the illustration. Up to now, the fan speed was controlled by having the water temperature switch control the fan relay. Currently, some engine ECUs control the fan relay to control the fan speed, or the cooling fan ECU to control the fan speed.

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PostPosted: Wed Jul 25, 2012 3:33 pm 
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Junior WRC

Joined: Fri Jan 29, 2010 10:39 pm
Posts: 514
Location: Bournemouth
Car Model: ST205
sounds to me like the ACT pin is an OUTPUT from the ecu so should not affect performance unless this output is fed back IN somewhere further down the line.....

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PostPosted: Thu Jul 26, 2012 5:45 am 
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Junior WRC

Joined: Tue May 23, 2006 8:06 pm
Posts: 595
Location: Knoxville, TN USA
Car Model: None
Thanks for the reply. An update since then, my AC is not turning on now at all even with the ACT wire removed. I need to inspect the compressor. However, the car does not run funny anymore with the ACT wire removed. At the time when I first made this post I had some vacuum issues as well as code 54. Those have since been resolved and may have been largely to blame for the car running poorly. After I do my brake upgrade I will diagnose the compressor then put a switch on the ACT wire in case I need to reactivate it.

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1992 Celica Gt4 RC Conv. St205 swap
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PostPosted: Thu Jul 26, 2012 10:44 am 
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Group B
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Joined: Sat Sep 02, 2006 3:13 pm
Posts: 3679
Location: Bournemouth
Car Model: None
Quote:
The engine ECU turns OFF the A/C compressor in accordance with vehicle conditions to maintain good drivability and acceleration performance.


Interesting. I re-gassed my aircon yesterday following a pump change a while back and it's nowhere near as cold as it used to be. I was putting it down to a poor pump (rumbling bearing noise when running) but now wondering if it's related to having fitted an aftermarket ECU and whether this is no longer telling the aircon to run flat out.

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