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Discussion Starter · #1 ·
I know it seems like my car is full of problems but this issue has been bothering me for over a year. Whenever I turn on my A/C, the battery voltage drops down below the halfway point (less than 13V) when the engine is idling. When the car starts moving again, the voltage increases. Thinking the problem was with the alternator, I replaced it a few months ago and it was still doing it (the new alternator tested 140A at 2000rpms). I later replaced the battery with an Optima; no luck. As a last resort, I ordered the voltage boost mod from ZZP to eradicate it-still nothing (the voltage swings even more at idle). The A/C works-it's cold-but whenever I turn it on, the engine seems like it's lugging a trailer. I'm absolutely stumped on this one.
 

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That is kind of normal. I don't know exactly how much it is supposed to drop, but it will. That an electromagnetic clutch, so it's gonna draw power, and then the blower motor takes a lot of juice, too. Check the grounds, and maybe upgrade the wiring between the alternator and the battery, and check all your grounds.

As far as not feeling as powerful when you're driving that is absolutely normal. You should feel the difference in my Volvo! It's miserable. You're sapping A LOT of horsepower to run that air compressor. I forget how much, but from 25-50HP can be taken by one.
 

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sorry but its normal like DE137 said. YOu can do the ALT re-wire but with the luxury of A/c voltage pays the price
 

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Sorry man, thats pretty normal for the technology. The entire system draws a lot of electrical energy causing the alternator to drag down the engine on top of the drag the compressor causes.
 

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Im just wondering if another 100 to 200 rpm at idle would help with your charging problem.
 

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Im just wondering if another 100 to 200 rpm at idle would help with your charging problem.
Yes, it will...but the real reason it is doing it is a parameter in the PCM. The engine commands the alt off under a certain idle RPM. When the AC is on, the PCM is supposed to command a higher idle to avoid this, but if the car has other mods that may be interfering with this; well, you see where I'm going.

IIRC the stock idle is set to 750ishRPM, and the alt cutoff is 700.

I turned my alt cutoff down to 500rpm, and it never dims at idle anymore.
 

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Discussion Starter · #7 ·
My car is bone stock but it idles at 650rpms. If I increase the idle rpms (there is a snap ring on the side of the throttle body for adjusting idle) then I may be able to allow the alternator to keep distributing current. Sounds like a plan-I'll see if setting it to 750rpms will work.
 

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It doesnt work that way. If you turn the screw to increase the idle, the IAC will turn itself inward and slow the idle back down and set a check engine light.
 

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:dito: there no way of adjusting idle with these cars. They all use a computer controlled idle so no matter what and if its out of spec. your going into retard mode with your car
 

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Idle can be adjusted with a tuning program.
I also have my idle bumped up 50 RPMs and the alt cut off at 500 RPMs.
No more dimming when the clutch kicks on or when the idle does the little dip when you quickly release the throttle.
 

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Yeah, if your going to be doing other mods to your car invest in a tuner now, youll be needing it. Otherwise you could have a PCM programmed to bump the idle.
 
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