The air conditioning system in my car won't turn on. I pulled the compressor clutch relay and verified that the relay works. There is voltage to the relay socket. If I use a wire to short the contact terminals in the relay socket, the compressor engages and cold air comes out of the vents. The blower motor seems fine, as there is plenty of air coming out of the vents. It's just not cold.
All fuses are fine, and the green light above the AC button goes on and off when you hit the button.

Is this an ECM/PCM problem? Check Engine is not lit.

gnunes
2004 Accord 2.4L DX MT

 

Do both radiator fans turn on when you turn on the a/c?

I'd start testing on the compressor relay socket. The high current side has two pins. One will have power, the other pin feeds the compressor clutch coil. Sounds like you jumped these two pins and got the compressor to turn on, so the high current side of the circuit is good.

The other two pins on the relay are the control side. One pin should have 12V and the other pin will be open to ground with the a/c turned off. It will be closed to ground with the a/c turned on. Test those pins with a volt meter and let us know what you find.

 

Both radiator fans are on. The voltages are present, but the other control terminal stays open, whether the AC is turned on or not.

 

try testing for hvac codes described in this thread.

https://www.hondaaccordforum.com/for...94/#post370304

 

Ran the diagnostic (for Accords without climate control). The system passes (no blinks, either of the recirc light or the A/C light).

 

And a follow up question: Am I correct in assuming that without climate control, there is no system that turns the A/C on and off with cabin temperature? The A/C is either on or off, depending on the status of the dashboard button?

 

I'm not sure that is true. All accords have a temperature sensor in the evaporator that can shut off the a/c system if the temperature gets out of range.

Here are the next tests I would try. Find the a/c pressure switch, unplug the electrical connector, then test for continuity between the switch terminals. The blue/red wire should have 12V to ground with the key in the II position.

 

See attached diagram.

Sounds like no ground signal to AC relay from ECM. Several possibilities; pressure switch, AC diode, thermostat, Auto Trans (not sure about link, see wiring diagram), body ground. More likely culprits are pressure switch and thermostat. Note, ECM gets input from AC circuit and enables AC relay w/ a ground. No direct link.

good luck

 

Will a pressure switch or thermostat cause the climate control to shut off while driving?