This is a 2000 civic si EM1 with a jdm b18c swap (obd1 jdm ecu).. just redid the ac system... replaced the ac compressor and drier.. notice the condenser fan and compressor is ALWAYS on as soon as i start the car.. doesnt cycle on/off.. even when i hit the ac button is doesnt turn off.. ive replaced the condenser relay and clutch relay.. same problem.. ive disconnected the heater/ac control panel.. its still running.. checked the ac diode and its good.. cant figure out whats keeping the system on running .. if anyone can help pls..

Bump..

 

Bump

 

The control panel pulls a wire to ground, which energizes the condenser fan relay, if the pressure switch is closed the ground is detected at the ECU and turns on the compressor.

I think the 2000 has the evaporator temperature control through the control panel. Older models have a thermostat in series with the control wire between the control panel and the stuff under the hood.

Basically, that wire must be shorted to ground. Or someone has modified the wiring.

When you "unplugged the control panel", was it the main part with the dials or just the little part with the three buttons? Because the computer that decides if the compressor is going to run is in the main part. Unplugging just the three button part won't stop it. The control panel being a computer-based part, it is advisable to turn the key off and disconnect the battery before unplugging or re-plugging it.

You could start by unplugging the pressure switch. If the short is before the switch, the compressor will stop but fan keep running. If the short is after the switch the fan will stop but compressor keep running. Plug it back in immediately if that happens or the high side will overpressure!

Note that the compressor will run if "defrost" air outlet is selected on the control panel, even if the A/C button is not pressed.

 

Thanks for replying mk378.. shouldnt the system turn off when i disconnect the control panel?.. i also dosconnected the ecu.. and when on KOEO i hear the condenser fan on.. its so weird. . Ill try look into it again.. thanks again

 

If the wire is shorted to ground the condenser fan will still come on even with ECU and control panel disconnected. The compressor depends on going through the ECU-- if compressor is still trying to pull in with ECU disconnected I would suspect something is modified or miswired.

Do some power-off tests with an ohmmeter-- disconnect the battery, pull the ECU, panel and relay so there should be no path from the control wire to anywhere.

Of course look at a schematic for wire colors and actual connections. I'm just going by memory.

 

thanks again mk.. i disconnected the pressure switch.. condensor fan turned off and compressor still running.. ill definitely follow your instructions. . But as for now i cant.. its my DD.. i removed the 20 amp fuse that powers the circuit, just so i can drice it... but man this is tripping me out.. thanks again mk..

 

It could be a problem in the ECU. I had a problem once where the A/C clutch was always engaged, and traced the problem to a bad transistor array in the ECU - one of the transistors was "stuck closed". The fix involved removing and replacing the chip (you might need some soldering and electronics experience to test for and fix this). I posted about it here:

https://honda-tech.com/forums/honda-...lways-3274699/

However, if your AC clutch is still engaged even with the ECU removed, then you probably have a short to ground on one of the wires to the compressor. Also I can't remember for sure but I think the condenser fan is not controlled by the ecu. Maybe you might have two separate problems.