a/c on causes battery level to drop to 9V

**Anwazi** · 09-28-2009, 10:58 AM

Ok, so when i turn my a/c on the engine sounds like it's knocking, but very faint knocking sounds. worries me a tad. also when i'm at idle w/ac on the battery gauge reads waaay low. maybe in the 9-10 volt area. in the yellow anyway.

also, what does everyone's temp gauge read during normal driving. Mine sits between 160-180, but with A/C on it starts climbing further up, but always below 200 degrees. is this normal or did the owner before me put in a different thermostat??

**HUNTNFISH** · 09-28-2009, 11:12 AM

Mine does the same thing. But only when you pull up to a red light and then it will go back to 13 volts when you take off.
Temperature does the same as yours.
I do not hear a knocking though.......

**Anwazi** · 09-28-2009, 11:29 AM

it used to power down like that without the a/c on and would shut off at red lights. ended up being a vacuum leak and bad alternator. i changed the alternator. the vacuum leak was a result of my instructor (who tuned the car) turning off my EGR system. I finally got a little kit off ebay, took the egr off and sealed holes with kit. no more vacuum leak.
Now, i'm wondering if the a/c compressor is having issues or is draining alot of the electrical power when at idle (corrosion, bad wires,etc). When i take off it goes back to normal levels. maybe the faint knocking is from not enough power going to the spark plugs due to the low battery level.......???
or...since the temp gauge reads higher during a/c use, the excess heat in the engine is causing pre-ignition.

someone help!