Is. 5.7 Ls1 Conversion ,a/c Issues

[Is5700]

Hi everyone ,

I've just completed a ls1 6 speed conversion, in a 2001 is200 everything works perfect , only issue is I can't get the climate control to activate the a/c compressor. I'm assuming it's because the can bus can't see the original engine turning over. The original ecu is still in place so it can transmit water temp and battery data to the dash, I've tried sending a pulse to the ecu via the original cas wiring but it didn't work, I'm open to suggestions, worst case I'll fit a new a/ c switch but then the climate control won't cycle the compressor when required to prevent icing of the evaporator ?

[wastegate]

Have a chat to Clayton (bahaimus) on Performance Forums, he is doing a LS3 conversion on his IS200. He believes he has sorted his Aircon. Something to do with using a Ray Hall signal generator to fool the IS ecu into thinking it's running at 2000rpm.

[Is5700]

Already found him thx , and yes it seems a signal generator is all that's required to make the Ac think the engine is turning ( hopefully)

[bahaimus]

The Lexus ECU needs to see a 36-2 signal. Not just any old crank angle signal.

[ISmarcus]

And some other feedback too so the fuel gauge will work. You know you have it when the econo gauge starts to work. Circuit diagram is available on the internerd. The stock computer needs to think the factory engine is running without major codes. That takes a few signals in. As bahaimus says 36-2 crank signal, a couple of feedback signals and it all works. Not sure why you would get an rpm signal tricker. If you supply the right signal to the factory computer it will run the tacho for you too. If you mess with the inputs to the factory computer enough, the fuel gauge even reads right for the V8. I have fiddled with the calibration untill the fuel light comes on with 10 lites left with a 6liter . Close enough to stock, I think. My engine is drive by wire with the factory pedal, but that is another story.