Bad Alternator or Battery??

[basit701]

Hello Guys! I own a Toyota Vitz (Yaris) 1KR-FE (CVT). From past few days i am facing problems like dimming lights, vibration when AC or headlights turn on. To diagnose this i checked my battery(approx 2 year old) voltage and DMM was showing about 12.2V. I replaced the battery with new AC Delco sealed maintenance free battery. After changing the battery i am facing these issues.

The engine would crank in the morning and if i turn off and crank again. It would start. But if i drive like 5 6 KM with AC on and turn off the car and start again. The car would take a heavy start like the battery is dead. So i checked the voltage of battery at different instants and these are the results:

Voltage when engine off: 13.08V
Voltage when engine runs after cranking: 13.67V
Voltage after 2 3 minutes of emgine running : 13.34V
Increasing RPM to 2000~2500 voltage after 4 5 minutes of engine running: 13.7V
Turning AC and headlights on @ idle:13.15V and @2000~2500 rpm: 13.28V

I am just confused is the alternator weak or battery is bad(AC Delco is a reputed brand and also the hydrometer on the battery is green which means OK).

Any suggestions???

[CTScott]

It looks like your new battery and alternator are fine. If it is a second generation Vitz (2005-2011), then the problem may be that you need to clean the throttle body. When you disconnect the battery the ECM loses its short term data and if there are deposits of carbon in the throttle body, then the idle gets off a bit, making the car run a bit rough when starting.

[basit701]

Yes its a Second Generation Vitz. But the thing concerning me is that after driving for like 5 6 KM with AC on and then starting again, why the car take a heavy start?

[Exiwolfman]

Originally Posted by CTScott

It looks like your new battery and alternator are fine. If it is a second generation Vitz (2005-2011), then the problem may be that you need to clean the throttle body. When you disconnect the battery the ECM loses its short term data and if there are deposits of carbon in the throttle body, then the idle gets off a bit, making the car run a bit rough when starting.

second this , carb build up and after battery change it resets the throttle body plate and makes the car run ruff . This is a problem i find with all by-wire throttles . Clean Your throttle body but with key on and gas pedal pushed in to open it do not move it by hand or you will get and engine code.

[basit701]

Clean with what? Carburetor/Injector cleaner? Or clean cloth?

[Exiwolfman]

Originally Posted by basit701

Clean with what? Carburetor/Injector cleaner? Or clean cloth?

both and an old tooth brush so u can get inside little better.

[basit701]

Got the throttle body cleaned. Problem is still there. I think startor motor is faulty??

[basit701]

Bump!

[Exiwolfman]

Starter motor has nothing to do with drivibility it only starts your engine.

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[CTScott]

Originally Posted by basit701

Got the throttle body cleaned. Problem is still there. I think startor motor is faulty??

Considering that battery voltages look good in various states, check the terminals of it to make sure they are not corroded and check the ground connections from the battery to the chassis and between the engine and the chassis.

[basit701]

Originally Posted by CTScott

Considering that battery voltages look good in various states, check the terminals of it to make sure they are not corroded and check the ground connections from the battery to the chassis and between the engine and the chassis.

I changed the battery terminals with the same JDM one they were clean and battery is also new so its terminals are also clean. The connection is tight and firm.

I checked the resistances between different points like Chasis and battery ground and engine and battery ground. Its like 0.1 or 0.2ohm. When i connect the DMM at first reading is like 10 12 ohm and it falls gradually to 0.1 or 0.2 ohm.

What i suspect from these results is
1) Either cables ground and positve are weak when hot. This analogy is from the weak AC compressor clutch wire. The original AC wire used to trip the compressor so i installed a relay long time ago and it works like a charm.

2)Starter motor issue.

3) Alternator issue.(I will get a JDM alternator just for checking in the evening to check whether the problem gets eradicated)

Another question: Where is the starter relay connected in Vitz(Yaris). Relay contacts might have worn.

[basit701]

LATEST DEVELOPMENT:

Being obsessed by the problem i opened the terrminals and found something. One of the fuse on positive terminal "ALT" was blown and some one had bypassed it on "Main" by connection of wire loop (2 to 3mm2). Is this can be the problem? I suspect ALT is alternator amps.

[CTScott]

Originally Posted by basit701

LATEST DEVELOPMENT:

Being obsessed by the problem i opened the terrminals and found something. One of the fuse on positive terminal "ALT" was blown and some one had bypassed it on "Main" by connection of wire loop (2 to 3mm2). Is this can be the problem? I suspect ALT is alternator amps.

MAIN is the main feed from the battery to the car and ALT is the feed from the alternator to the battery. It is unlikely that that bypass is the issue, as they both go directly to the battery terminal, but I would replace it for safety's sake.

[basit701]

CT Scott i one thing more i have observed. When i start tha car the voltage at battery terminals is 13.89 or 14 Volts. However when the engine is hot (to temp that fan triggers) the voltage at terminals is 13.25 Volts and when i turn off the engine the battery voltage is 13.02. Now 13.25-13.02 = 0.23 Volt. Isn't its less. Same problem has been observed when alternator was temporarily replaced.

[CTScott]

Originally Posted by basit701

CT Scott i one thing more i have observed. When i start tha car the voltage at battery terminals is 13.89 or 14 Volts. However when the engine is hot (to temp that fan triggers) the voltage at terminals is 13.25 Volts and when i turn off the engine the battery voltage is 13.02. Now 13.25-13.02 = 0.23 Volt. Isn't its less. Same problem has been observed when alternator was temporarily replaced.

Those voltages are OK.

[Exiwolfman]

Think someone has OCD

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[IllusionX]

Originally Posted by Exiwolfman

Think someone has OCD

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I read this thread again. You may be right.

My Yaris doesn't start the same when the car is warm vs when it sat over night.

The Yaris should start even at 11v... It is very unlikely the .25v difference is going to cause issues.

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[basit701]

okay Guys the problem has been solved. The culprit was Starter Motor. Its bushes were worn and the armature was not intact between the bushes. Changed the bushes and its YOOOOO