I have a 1999 Accord EX-V6 that has had a cursed A/C system for years! I bought the car used so I don't know if it has always had this problem or not. The short story is the A/C compressor is always engaged (the wire is always hot.) The system has been to a few mechanics and has had many parts replaced over the years, but no one, not even the dealer has been able to fix it. Tonight I tried my last idea which didn't work (new ECM), so here I am!

The compressor has been replaced twice (I think I blew two because they were on all the time.) It has had a new condenser installed, along with 2 expansion valves and driers. I've run a wire from the clutch relay and it's always hot when the key is on. Pulling the clutch relay disconnects the clutch, as does pulling the fuse for the relay at the driver door panel. With the pressure switch on the drier and/or the temperature bulb on the evaporator core disconnected the clutch still is engaged. Today I plugged in a new ECM, and even though the car won't start (just crank), there is still power to the compressor when the key is turned to on. (It doesn't matter what the HVAC panel is set to: off, full auto, a/c off, a/c on, heat set to max, etc.) The HVAC panel has also been replaced. It's been awhile, but I think it also remains on even if the HVAC panel is completely disconnected. Removing any of the other relays (blower, fans, etc) has no impact.

The last thing I can think to try is to test the signal directly from the ECM, but something tells me it's going to be hot. I'll see if I can track down where to find the wire on the harness.

Any other suggestions? Last summer I ran a wire from the compressor relay to my dash so I can manually cycle it on and off. A very elegant solution!

 

have you tried a new compressor relay? are you familiar with how a relay works and how to test one? it might be as simple as a stuck "on" relay. if there are other relays that are the same, you can try swapping the compressor relay with some other relay... if the compressor behaves normally, you've found your problem.

 

Are both fans running all of the time too?

 

I've picked up a new relay and swapped them all around.

Both fans *will* run, but they seem to work as intended (they're not on all the time and the condenser fan can cycle independently of the radiator fan.) The condenser fan will only run when the a/c switch is set to full auto (and the a/c should be running) or when the a/c is set to on.

The fans are not running when the engine is not running but the key is set to on. The ECM seems to be compensating (raising and lowering RPMs) for the A/C running when the A/C is turned on and off via the switch, even though the clutch remains engaged (though the fan will turn on and off on the condenser).

 

My guess is that the wire that the PCM grounds to turn on the relay is shorted to ground between the relay plug and the PCM.

This information is from the spoon site that I posted in the Online Manuals thread in the DIY section.

It looks like there are 4 wires going to the compressor relay plug. blk/orn, red, red, and ?.

One of the two red wires is grounded by the PCM at pin A17. If you unplug the PCM, you should read an open circuit on one of the red wires. If you do not, then the red wire is touching metal or ground somewhere.

 

So far so good, I removed wire A17 and the compressor is still engaging. Running a new wire, will report back!

 

So I cut A17 at the PCM and at the relay/fuse box and ran a new wire. That fixed the problem of the compressor always running, now I think it's never running. Turning the a/c **** to max cool and toggling the a/c button on and off doesn't seem to do anything (no movement of the tach either.)

 

Do you have a shop manual for your accord?

 

A Haynes manual.

 

The pin number that I gave you may have been from a 4 cylinder, so you may have bypassed the wrong wire at the PCM.