When i'm in neutral and my a/c is on, i hear a clicking noise in the engine bay that engages every 5-10 seconds. When the clicking sound happens my idle drops to a little lower than 500rpm and the car shakes like hell. It reminds me of when you leave your car in gear by accident sometimes and brake w/o hitting the clutch. Also, when idle speed drops, the electrical systems dim.

However, when i'm in neutral w/o a/c the car is fine and idling at 725rpm.....my haynes manual says the car should idle between 650-750rpm. A friend said i should just adjust the idle speed to go higher but won't that mess up my engine?

 

oh yeah.....the car is a 96 manual accord sedan

 

well, your a/c will make a slight clicking sound when it turns on and off. (the a/c doesn't actually stay on 100% of the time your a/c button is on. i think it's more like 50/50) when the compressor kicks back on, the car has to work harder to keep the idle speed up... it sounds to me like your ecu isn't recognizing the fact the your a/c is on and it's not compensating for it. that would cause your idle to drop.

your alternator charges at 100% when it reaches 1000rpm, or somewhere around there. 100% meaning roughly 14.4 volts. at 750 rpm, it's probably around 12 or 13 volts. when your idle drops to 500 rpm, it's not really producing enough current to power the car, causing the lights to dim.

don't just raise your idle... take it to a shop and have it looked at. it might just be something as simple as a loose wire somewhere.

 

I agree, but would add that you should have the A/C compressor clutch checked out as well. it shouldn't be kicking on/off that often.

 

Watch the AC compressor clutch while it's idling. You can see it engage & disengage. Is it really the AC doing it's thing?

If so, then it's cycling too fast (5 or 10 seconds!) Somethings wrong with it. Overcharged? Undercharged? Bad compressor bearings?

Even cycling too fast, the ECU should be able to hold a steady idle by opening the IAC valve. Maybe that's stuck or dirty or something.

 

you need to hook up a guage set to the AC system and get some numbers

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jerseybrandon &raquo;</TD></TR><TR><TD CLASS="quote">you need to hook up a guage set to the AC system and get some numbers</TD></TR></TABLE>If it's going every 5 or 10 seconds, I want him to verify that it's REALLY the AC compressor cycling, before going off on a wild-goose chase. You can see the clutch engage & disengage.

Yes, if it really is the AC, you gotta measure pressures. Don't just get a can of refrigerant & screw around.

 

i had the same problem, it ended up being that my expansion valve which is near the condenser was bad, i had that replaced, recharged it, and the also replaced the reciever dryer and everything worked great until i totalled my car. everything including labor was like 300 something dollars. i hope this helps. take it to an ac shop and have them run a diagnostic on it. my clicking noise was more like a popping noise. and my car would almost cut off, you could also feel the power drop off driving down the road.

 

thanx for the great replys....this place blows the other forums away as great tangible answers to problems....i'll get a diagnostic on the car with a pro and go from there