So I have been noticing recently the system voltage is down. When my car is hot Im seeing 13.0-13.4 volts idling/cruising. When it gets really hot like a couple weeks ago at the track I was only seeing 12.8 volts. During WOT I never see above 12.9ish when during the winter it would normaly be charging much higher like in the 13.6 range and 14.0 when Id first fire it up.

Today I went out with a multimeter and found the battery holding 12.55 volts with the car off. Just turning accessories(no radio or fans) on I found 11.8 volts at the battery but on my scanmaster it was showing 11.4 so even lower at the PCM. So then I fired it up and at idle I was seeing 13.7 at the battery and 14.01 coming from the alternator with a system voltage of 13.4-13.0(fluctuating). Where am I losing all the voltage at? It kinda looks like the battery cable from the alternator might be loose or corroded causing that .3 volt loss but its not. So Im not sure if the demand on the battery is what is what was giving me that lower reading or the battery cable itself showing the signs of aging.

A buddy of mine believes it the ignition switch since apparently power to basically everything runs right thru that switch. Sorry this post is kidna long but I gotta be specific so what do you guys think? Is this normal or should I be concerned?

 

Nobody else has this problem??

 

im runnin a fat system and i constantly get 11 volts. i'm jealous of ur voltage

 

I am a non traditional electronics/laser student right now. If your battery is starting to read a little low, it is probably just strating to wear out. If it's new, I would try to take it back, because it could be poor quality. If it's old, it is probably starting to not hold a good charge, and will eventually lose it's ability to take as much charge as a good battery. Sorry I can't give a more definitive answer. Or maybee your alternator is not up to par either.

ZMAN

 

Take it to Sears and they will load test your bat and charging system while ya wait.
Low voltage in to alternator-- low voltage out.

 

yo turbo z, i am so glad you posted because my car has THE SAME IDENTICAL PROBLEM. tell me if this sounds familiar---

1) weird voltage, occasionally runs normally but for the most parts runs and idles around 11.5 volts

2) radio/windows sometimes dont work on startup

3) ignition switch feels locked at startup sometimes

I just called a pontiac dealer and they said a new switch is $37 and the lock cylinder is $98. they dont neccessarily need to be purchased together, depending on how back your ignition is, however i am just assuming i will need both, because my car is acting completely weird. i also have a monster tach from autometer and the light comes on, but it doesnt read any rpms, it just stays stuck

let me know what you think.

BRIAN

 

That battery is on it's way out. You have described a classic symptom. It'll probably load test good, so I wouldn't worry too much right now. I've had em last up to a year at this point. But the very first time you hear it crank slow, replace it.

Bet your windows are working slower too. They're probably a better indicator than the volt gauge.

Good Luck!

 

Sounds like ya got 2 differant problems.

1-The voltige thing is one,like I said take it to Sears and if the bat is bad the check is free if ya buy a DiehHard.Either way ya will know if it's the bat or alternator.
2-That could very well be the ign switch on the switch side not making contact.
3-That is probably wear on the tumbler

I would replace both the switch and key tumbler,ya will have to get your new key reprogramed for your anti theft(I think).
Replacing the switch isn't an easy task so ya might want to get someone to do it for ya.

Have ya got the tach wired correctly??

 

The battery and alternator are only a few months old. The alternator is fine.. it tested fine as far as I can tell 14.10 volts is right on par with what i should be seeing.

Everything seems to work fine. What Im really concerned about is insufficient voltage to the fuel pump and maybe a weaker spark.

 

Are ya getting 14V at the junction inside the red box with it reved up to 2500 or so?

 

The red box junction was the same voltage as the battery. A minute ago when I checked again I was seeing 14.10 volts at the back of the alternator.. 13.96 volts at the battery and the same at the junction.

 

Do this: take readings while the engine is running at the battery and at some fuses that are only powerd through the ignition switch and compare them.

Commonly, there is some voltage drop through the ignition switch, especially in hot temperatures (in my experience). I have an idea on how to correct the situation, but have not had time to implement it and test it out.

You can always check/replace the ignition switch and check the tightness of the connections there. The main power connector on the switch often looks heat damaged and may be loose.

 

Was that idle or reved?

 

That was at idle.


Shoebox,

Any fuse labled ignition or fuel should run thru the ignition switch correct?

 

Tell ya what---
Connect your volt meter across the bat and put it on the windshield. Crank it up and run @2000 with nothing on until voltage stabilizes at 14V. Hold the RPM's and turn on the headlight's then the air. If the voltage falls and it won't support a load,there are 3 things=
1=Low battery V
2= bad diode in alt
3=bad voltage regulator-- amps set to low or not working.

2&3 replace alt or repair
1-charge and check bat.

As Shoe mentioned ya may have a connection problem at the ign switch.If the bat won't stay up and everything checks out-run a #10 wire from the alt+ direct to bat+ and that will eliminate the bat problem, by charging the bat direct instead of through connections, but not "any" or "the" connection problems to the rest of the car if any.
Connection problems will have to be run down one by one.