| I grounded pin 46 of the ECU in order to disable the TCA. Doing this brought back adequate cooling but also activated the FICD (fast idle control device) and the compressor, which now runs all the time, even with the a/c shut off. Three air flows into the engine are independently controlled. The separate AAC (auxiliary air control); the modern choke of the engine, and the combined IACV-FICD (idle air control valve-fast idle control device). Turning on the A/C activates the FCID and raises the idle speed. Why the IACV under the command of the ECU does not mainatain 750 is beyond me. Apparently the FICD is uncontrolled and is just a hole opening. It also possible the instructions of the ECU select 900 rpm with the air on. I will soon determine this when I put a switch on that ground so I can disconnect it when the air is not being used. The TCA is fitted only to 1994 and later cars with r134a. Nissan retains use of this system configuration to this day. I have seen plenty of discussions on other fora related to poor cooling and the TCA. Never on this forum. Guess there aren't that many of these later cars. The TCA introduced into the Nissan a/c systems a form quasi-clutch cycling. Orifice tube (accumulator pressure controlled evap temp) and traditional oil-filled bulb controlled evap temp; CYCLE the clutch magnet on-and off. Nissan systems DO NOT (never in r12) cycle the clutch except via the TCA on the rare occasions when the exp/by-pass valve fails to keep the evap temp above 34F. Nissan controls evap temp by diverting the refrigerant away from the evap. Not sure I like it but it is what it is.
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