The AC - of my 2008 Civic - stopped working so my son replaced the compressor/clutch. Now the AC wont turn off, it idles very rough, and surges when moving. Seems like something is causing the clutch to engage and disengage randomly. This only happens when the AC is on... I know this because when I pulled the relay, the engine purrs like a kitten.

The refrigerant level is fine. The car gets cold. A new relay didn't help. Not sure what to look at next.

 

My car Ac is good and when I am at a light or stopped and the Ac cycles makes the car engine vibrate and idle drops for a second. Seems normal to me. This will also cause the car to try to surge forward when stop when it clicks on, as the idle compensates.
If the Ac is staying on all the time, you might have some type of electrical or ac/clutch issue.

 

check the clutch air gap

 

The compressor/clutch are brand new. My son thought it might be bad so he took it back and got another. Same story.

 

your original post is hard to understand cause you say the ac won't turn off but the compressor keeps engaging randomly

can you be more specific and detailed about whats happening

 

My guess is that he's talking about the compressor cycling on and off.

 

holmesnmany - Yes sorry, somewhat confusing.

Yes, the AC cannot be turned off. The AC button does nothing. When the car starts the AC is engaged all the time. Now, while the car is running, the idle hunts up and down by as much as 500 rpm. and when the car is moving, the engine will surge and pull back in response to the rpm fluctuations. I think that this is the AC clutch going in and out but it may be something else. This has been happening for about 2 years before the compressor/clutch gave out.

When the engine is cold, the car runs smoothly. However as it warms up the idle problems surface.

 

if the clutch never shuts off then you need to disconnect the coil connector, if the clutch is still on then you need to check the clutch air gap, but if the clutch disengaged then the ac relay is likely bad stuck in the on position, which means it's an Omron and needs to be replaced with the Mitsuba one which is a known issue with these cars

 

I'll try to disconnect the coil.

I did disconnect the relay and the clutch disengaged. I replaced it with an Omron which didn't do anything. Maybe I should look for a Mitsuba?

 

you said you disconnected the relay and the clutch disengaged but when you replaced the relay it engaged again ? is the defroster on ? the ac actually turns on when you have the defroster on, most people don't know this

 

When the car is on, the AC is on except that the clutch will constantly engage and disengage. There is no way to shut it off using the HVAC control panel. Fan off, green light off, no defroster etc. The only way to stop it is to kill power to the clutch like removing the relay or to shut the car off.

So basically the AC is always on but the clutch engages and disengages constantly causing the idle to jump all over the place.

 

when you say you replaced the relay with an Omron, was that a different one that the one that was originally in there or you put back the Omron ?

if it's a new one and still doing it then something is giving power to the relay when the ignition is on, are the fans also running when it's acting up ? if they are then I gotta think it's the climate control unit sticking on with power to the ac system

i think if the ecu was telling the system to turn on then it would adjust the idle accordingly so it's likely downstream of the ecu

 

This weird thing has happened to me a couple of times. Car sat overnight, then when I went to turn it on, the AC would engage. No matter if the fan was off or AC button off or defroster button was off. I would assume that it was the relay, but it has only happened to me a couple of times.

 

After an extensive investigation I am going to try:

1. Check if the there is too much refrigerant . I have read in older threads that this could cause the rough idle.
2. Pull the connection to the climate controls. I am not sure that this will help because when I push the AC button, the led goes on and off. However the led could be the only thing working on this system.