New alternator but battery light almost ON

[Rahul Jones]

Hey guys,

I just replaced the alternator in my mom’s 2005 Toyota Camry as it died out. Now I have got the battery recharged from a nearby shop and still the battery light stays almost ON. But the light goes away if I removed the connector to the alternator. Is the voltage regulator on the new alternator faulty (it is remanufactured unit)? But the battery is being charged as normal and it is putting enough power with load. Also, is it normal for the alternator to get hot that it cannot be touched? I will attach the pic of the instrument cluster warning you compare the battery light with the parking brake light to see the brightness.

Thanks in advance,

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[college man]

seeing the the battery light goes off when you unplug the connector the wiring is ok.
Two possibilities here. Your battery is having a problem causing the alternator not to
put out or your reman alternator is bad. see if this link helps on checking your charging
system.

http://www.ericthecarguy.com/faq/solving-automotive-electrical-problems

[Its me]

What is the voltage at the battery when the light is on?

May be as you suspect. A bad diode/regulator on the generator.

-Karl

[Rahul Jones]

Voltage is always over 13.8V. I don’t know if I should just continue using the same alternator or if I should ask for a replacement. It is very painful to put the drive belt back on.

[Andrew Harris]

Voltage travels through the battery light bulb and down to the alternator. the alt grounds the wire to turn the light bulb on if their is a problem with the alt. your alt is defective. I have seen this on many fords. sometimes the only way to get it to turn off is to use a factory alt.

[Andrew Phillips]

+1 on alternator. Many of the reman shops do not use internal parts (diodes, regulators, etc) that exactly match OE specifications. This is so they can get by with stocking fewer parts and making more money per unit. These are not so out-of-spec to prevent charging the battery, but they do manifest strange side effects such as the battery light dimly lit or flickering, whistling/humming, or otherwise just behaving badly.

[Charles]

You haven’t ruled out a bad battery. The battery voltage should hold and over 12VDC overnight. You might remove the negative battery cable from the battery while the engine is running and check the voltage out of the alternator to see what the float voltages is. Should be between 13.7 and 14.5 VDC.

[Andrew Phillips]

On modern vehicles one should NEVER remove the negative cable from the battery while the engine is running. This can fry the electronics in the cars. To rule out a bad battery, remove it from the vehicle and have it tested with the proper testing equipment.

[Andrew Harris]

The proper way to test the battery would be to load the battery with a carbon pile tester and load the battery with half the cold cranking amps of the battery. you don’t want battery voltage to fall below 9.5V. if it does your battery is bad. For a down and dirty test start and stop the engine 3 times and with a Min/Max function multimeter record your Min/max voltage on the third start. the min voltage should not fall under 9.5V again same thing. I would make sure your connection at the battery are clean and tight but if you are having a starting issues i would say your battery is fine. A bad alternator can kill a battery however as well as a bad battery can kill an alternator. I have never seen a battery light on in the dash because of a bad battery in a modern car. your problem lies with the alternator.

[Brian]

Most parts stores will do a free check of the charging system without removing anything. That would simplify your situation.
If it were me, I would check every end of every battery wires and connections. The starter is part of the charging circuit too, so get it checked for free just so you know.

[Author]

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