So something is effecting my car's voltage>

Basic overview:

2007 Scion tC
650.4 Kicker 4-channel Amp
750.1 Kicker Monoblock Amp
15 Farad Tsunami Capacitor
Optima Yellowtop Battery - since May 2009
12" DVC Kicker L7
2 sets of Polk MoMo 6.5 components

Answers to some of the basic questions:

1) Have I metered the battery while the car is running to check voltage? No
2) Have I taken the car to an auto store to have them put a load on either the battery or alternator? No
3) Have you ever replaced the alternator? No
4) Have you ever replaced the starter? Yes
5) What is the voltage reading when driving? Between 12.3 and 13.6, never into the 14's.
6) Who did the electrical work in the car? I did, i'm certified in mobile electronics. I worked as an installer for Circuit City, back when they were good and before they went out of business, before I graduated from undergrad and went on to grad school. I don't deal with shade tree electronics or mechanical guys.

Okay now that's out the way...

I'm pretty sure I know what the problem is but we're all here to learn so I wouldn't mind hearing what some of you guys have to say.

So the car will start sometimes but other times all you'll hear is the starter clicking but the car won't start. Now, when the car doesn't start the voltage, highly unreliable, on my RX65 radar detector and my ScanGauge will read roughly 11v.

I thought the problem was the battery so I went to Autozone and bought a cheap battery but before I went to install it I simply disconnected the battery, touched the terminals together to fully discharge the system and put them back on the battery and it started so I never installed the other battery, I ended up taking it back.

The problem doesn't happen all the time only and it is very sporadic, sometimes the car will fire right up other times I have to disconnect the battery and touch the terminals together then start it.

I do know, however, that the voltage on the scanguage and voltage on my RX65 read .5 - .7 volts off, when they do that I know when I turn the car off it is not going to start back up. When they both read practically the same within .1 - .3v of each other it'll fire back up, once again highly unscientific.

So i'm thinking the battery either has a bad cell, the alternator is failing or the capacitor is bad. The problem is, the sound system is custom built so I certainly don't want to pull it all out to get to the cap that is mounted in the spare tire well.

What do you guys think? I'll take the car to Autozone when I get off tomorrow and have them put a load on the battery to see if it is failing and if they have the tool that can put a load on the alternator I will have them test it too.

I figured it would be nice to see what you guys think.

 

U can try disconnecting the negative cable while the car is running. If the car dies then replace the alternator

 

I gotta get it to start again first.

The cap has been ruled out of the equation.

 

Negative post terminal removed, car still idles and runs. Albeit I can tell a little loss of constant voltage but none the less still runs.

 

Alternator has failed, only putting out 12v which isn't enough to charge the battery. For my needs I don't think I need a HO Alt so i'll be sourcing another OEM alt.

 

That's what the guy at Autozone told me which just still doesn't make any sense. I was getting more than 12v when I removed the negative terminal and metered the alternator. The car ran just fine and didn't die. I'm still thinking it's the battery but he tested both the battery and alternator using a tool and said the problem was the alternator.

 

You have a cap


But anyways!

Wasint there some issues with the fic drawing current! have you tried rulling that out?

 

An alternator is cheaper than a battery but the battery is easier to swap out than the alternator. Any ideas anyone?

 

LOL forget you Mike!

I didn't even think to try that. Is there a fix for that issue? Not like I can drive without the FIC.

 

Well i herd it was only on the auto tc's and i seen it first hand. yes there is a fix!

But you would be first manual tc to do it.. but hey im just thowing idears out there!

Did you like my stolen emoticon?

 

Interesting.....i'll go out to the car and unplug the FIC and give it a shot and I definitely do NOT like your emoticon.

 

Well that isn't the cause.

I checked to see if anything was pulling amperage from the battery while the car was off and nothing was.

I've unplugged my stereo system, gauges, FIC and the problem is still there.

So now i'm back to square 1.....either the battery or the alternator.

I hear a click, click, click when I try to start the car, sounds like the starter is trying to pump juice.

I have to leave the terminals off the battery for a little while before it'll start up.

 

It sounds like a loose connection to the motor preventing the starter from working properly and maybe the alternator from working fulling charging the battery with full voltage. I would start at the ground connections to the frame and starter motor bolts coming from the battery since removing them and reconnecting them has some effect. Shorting them together is not a good idea since it discharged caps in electronics throughout the car but you may also be partially welding the bad connection somewhere which causes it to work afterwards.
When measuring the battery voltage make sure you measure on the lead posts with the meter not on the clamps. Then measure between the positive of the battery and the positive output of the alternator when the engine is running to check for voltage drop and between the motor block alternator mount bracket and the negative terminal of the battery checking for voltage drop. Any large voltage drop (more than 0.1 volts) between these points indicates a bad connection between battery and motor. Lastly make sure the starter motor is bolted in tightly since you did change that. There were grounding kits for the battery negative to chassis connection to solve some tC issues.

 

I just followed up with Advanced Auto to have them check it with their machne, the guy there says the problem is definitely not the battery. He believes its the starter since the alternator is charging the battery sufficiently.

So now I have 2 conflicting views of what the issue is.

 

You can check your alternator easily by running the engine and turning on and off the headlights, rear electric defroster and heater fan on high. If the voltage only drops a little from 14 volts on the battery then the alternator is working, then turn them all off and the battery should return to 14.0 volts plus or minus a few tenths of a volt. Sounds more like a loose wire going to either ground or the starter so recheck the connections and the wire crimps on the lugs too. Make sure you have clean battery terminal contacts also!

 

Jan06xB you were right the entire time.

I had a loose connection at the battery and it was only starting when the connection was made. It took me taking the battery out of another car before figuring it out.

My car has an underdrive alternator pulley so it won't read the 14+ volts like on other cars, it will max at around ~14.1v but the alternator and battery read ~13.8v.

Anyway its all fixed now at the expense of me frying my LC-1 wideband in the process

 

With the high powered sound system you have you really don't want to be running an underdrive pulley on the alternator. That increases the field current in the rotor and lowers the efficiency of the alternator. If anything you want to drive it faster to keep the system voltage up to provide more power to the sound system otherwise you end up increasing the amp load on the battery and alternator for the same power for the amp with the slightly lower voltage. What you really need is a flex fan on the alternator to allow less drag at higher RPM and keep it cool with cold air.

You should also run heavier wire from the alternator to the battery to reduce the losses there since you are running 50+ amps probably all the time some 8 AWG wire would help or go crazy with some 6 AWG.