For a long while now the reading on the DIC for the volts has been "jumpy". What I mean is when I:

1. Roll down/up windows
2. brake
3. turn on AC
4. pretty much anything that requires electricity

The volts on my DIC jump down to the 13.3-13.7 range and then come back up to where it was... 14.0-14.2

All stereo equipment is stock... upgrades are in my profile (cam/intake/heads/exhaust/etc... no super charger/turbo)

If I sit and idle, the volts slowly come down... maybe .1 volts every couple minutes or so. Turning on AC/lights/etc cause it quicker. So, tonight I tried to completely kill my car by letting it idle with lights/AC/radio/blinkers on.

Eventually, the volt reading got all the way down to 12.8 and at times when I would roll windows up/down or something... it would jump as low as 11.8.

Last, if I cruise on the interstate, the volt reading comes back up to 14.0-14.1 range after a bit... but still displays the same jumping when I roll down a window or something.

The funny things is that none of the equipment stuttered... nor did the lights ever dim when the volts got real low. The only real problem I ran into was when the AC was on... I would rev and let it come back down to idle... it would drop to ~300-400 RPM (like it wanted to die) and then jump back to 800 RPM.

My battery and alternator (110 amp) were really old so I decided I would just replace those (probably time anyways). Well, after installing them and running for 20ish minutes, the same symptoms still happen.

What else could cause volts the jump around and drop? Bad ground somewhere? Is 110 amp alternator not enough. Any ideas are welcome.

 

Stop watching the voltage display and drive. You're trying too hard to find something wrong.

 

To be honest with you, what you're describing sounds pretty normal. This car has a high electrical appetite and its not designed to really sit ideling for extended periods with the lights an AC on. I know thats just a vague statement but if you try to let it sit with the maximum load on the system at the lowest charging level (actually at idle you're not really doing much charging) you're likely going to be able to drain it.

One thing I would check is the battery terminals (11 ft lbs) they sometimes feel pretty tight when battery is installed but they relly need to be to spec (not gorilla tight, but just up to spec) and Id also poke around a bit abd see if the ground point down on the frame (just look down inboard (towards the engine) past the battery and youll see a wire grounded to the frame).

Aside from that, you just did a lot of work no? (did alternator), might just want to go over the connections in general and make sure they are still clean and tight, its always the small things.

 

Clean the battery connections at the battery itself, then move down to the starter solenoid where you'll find the battery connections again and the negative cable bolted to the engine block. Not forgetting its electrically hot there, clean and tighten those connections too. Now there are two more areas to look at. One is a ground connection between the battery and fuse box down low on the frame. I understand that this one is where the DIC and other items gets a ground from. Also, the ignition switch itself may be starting to have isssues and there's been lots of reports of the contacts inside of it giving up.

 

When ever you use the windows, ac brakes it uses volts, It is normal to see what you see on the DIC.

 

As long as your connections are good and the alternator is working OK, what you are seeing is normal. As you put more load on the system, the voltage reading will vary.

 

Ok. Thanks everyone!

I guess I have just never seen a car drain like that when idling. Swapping out the battery and alternator was not much work at all... and it at least gives me a bit of piece of mind that they are new with warranty in case of failure.

I will go through the connections to make sure they are all clean and tight to spec.

Follow up question: assuming nothing is wrong with connections, etc... what would it take to "smooth" out the voltage --- not drain when idling? Would a 150 amp put out enough at idle with a larger load (such as AC and lights on)? Or could going with a smaller pulley on the alternator increase it's output at idle?

 

If you are pushing 13.3-13.7 when using ac, windows your car is fine, You are running a 12 volt system..

 

I can't think of any other way to tell you that nothing is wrong with your charge system. It doesn't need to be smoothed out. It just needs to keep your battery charged. If you were driving a car with an alternator light instead of a digital gauge, it could have varied a lot more than this and you would never have known it. Spend your time and money on something fun or useful. Select tire pressure and watch those vary if you need entertainment.

 

LOL. Ok.

I am just weird I guess. I'll switch the DIC to something different.

Me