i just installed universal EMS 30-1900u in 95 civic hb with OBD1. I noticed that the calibration included in the software is using switch#6 (ground = on) for the A/C master switch input (ECU pin B5), and the EMS is using LS#6 to drive the compressor clutch.
problem is, no matter if the A/C switch is turned on or off, it always send ground signal, which means switch#6 is always on when igntion is on, so does the LS#6 and compressor clutch.
the only data is this wire measure 12v when the A/C master switch is turned off, and measure 0.5v when the switch is turned on. But still, both conditions send ground signal.
I also already tried using switch#7 and used this voltage difference from pin#B5 as the input reference, it works. Only problem is, it require minimal set rpm to turned on, but it won't switch off until the engine speed is lower than this set rpm.
Any other clue how to control the A/C?