My compressor hasnt been engaging on my 95 civic dx with a 98 civic dx engine .So I checked everything as per the manual until i got to the part where you check the ecu connections but I dont have a test harness that you need so what do I do to get a/c.


also my 13 underdash fuse is a 10A instead of a 7.5A, does that affect anything?

 

You may be able to purchase the test harness online or from Honda. The 10A fuse won't affect circuit function but should be replaced with a 7.5A fuse to protect the circuit from possible damage. I assume you have a 98 Civic ECU, so I don't know whether the ECU tests in the 92 manual are applicable to your situation.

 

its the same 95 ecu

 

Does the condenser fan come on? The condenser fan does not go thru the ECU. The rest of this post assumes that the condenser fan comes on.

Does the engine idle up when you turn on the A/C? This indicates that the command to engage the compressor is reaching the ECU and it has responded to it.

If condenser fan runs but engine does not idle up, check continuity of the pressure switch on the line at the condenser. It should be closed. If it is open you probably have no refrigerant and the compressor will not work. If the switch is OK measure voltage at pin B5 of the ECU, should be some voltage with A/C off but go to near zero with A/C on.

If the engine does idle up, check for power reaching the wire to the compressor. If no power there check the compressor relay and pin A15 of the ECU (drives the relay by pulling to ground)

If power does reach the compressor, disconnect the wire and measure ohms thru the compressor to ground. Should be about 3 to 4 ohms. If open, either the coil or the thermo switch on compressor is bad.

If you have continuity thru the compressor but it doesn't engage, the clutch gap may be too wide.

 

The fan comes on and the engine idles up. the switch is good. I jumped the compressor and it turns engages. The relay is good and voltage is going the connector like this

() 12v () 12v white wire
() 4v () 0v red wire

No voltage is going to the red 1P connector from the ac wire harness going to the commpresor.

 

The 4 volts on the blac/red wire at the relay is su****ious, see if you have the same thing back at the other end of the wire at pin A15 of the ECU. Should be closer to zero. You should also swap the compressor relay with another one, such as the radiator fan relay located on the right fender. If it still doesn't work then yes I'd say it's a bad ECU.

 

I fixed it by grounding the black/red wire i dont know why it was reading 4v or it might have been human errorit now reads 0v.

PROBLEM SOLVED

 

Grounding that wire though, the compressor will never stop. That is not good.

 

it wont stop when i turn the a/c off?

 

No it will only stop when you turn the key off. Don't actually try that though, when you turn the A/C off the condenser fan will stop and that creates a minor Chernobyl under the hood. You have no protection against over pressure, so the lines or the relief valve will likely blow.