Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec Voltage drops when I put on the a/c at low rpms ..

I having a volatge drop I guess from the front to the back. When I try to start my car the distribution block up front shows a drop tp 9 volts while cranking of course the voltage is too low for pcm to crank up properly. Whenever I let the car sit for 30 minutes come back my voltage increases to 11 volts when cranking and starts up.

The car idles perfectly revs fine still rich but overeall runs. I monitor my voltage in the front and with the light on and tail lights and fan blower the volrage never drops past 13.9 but soon as I turn on the a/c the voltage drops to 12.9 12.5 and the car wants to stall. But if I give it gas the voltage comes up and the car smooth. Does the A/C pull that much power from the car?

Nevermind on the car stalling I forgot to hook up the idle control motor plug....... Easy to pass up little things like that...lol but I still have to figure out if the car chassis is enough for ground or run a seperate 2 guage ground. Plus I am going through a 200 amp bridge for my postive maybe I might have to setup a starter relay to engage over the fuse to elimanate volatage drop during cranking......

Don't worry about the AC pulling voltage when you turn it on, more likely the voltage is dropping because the rpm is dropping when the car tries to stall. Chances are the car is stalling because it's not tuned right. Fix that and then worry about the voltage when AC is on.

Also, check resistance on your starter cable and examine it for corrosion, or check your batter because 9 volts is pretty low.
Don't start riggin the stuff, fix it right by checking the correct stuff.