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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
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Have 2005 tundra with 4.7 it stopped charging so I had

Customer Question

have 2005 tundra with 4.7 it stopped charging so I had battery tested twice came out good. Had alternater installed still no charge . take battery cables off vehicle
Submitted: 1 year ago.
Category: Toyota
Expert:  Toyota Service replied 1 year ago.

Hello. Welcome to Just Answer. Please allwo me to assist you. Please go to the vehicle and open the fuse panel under the hood. Locate the ALT-S fuse on the panel (7.5 amps; top row on the right side). If this fuse is blown, the alternator will not charge. If the fuse is good, I would have the replacement alternator tested on the vehicle. Never have an alternator tested off of the vehicle.

Expert:  Toyota Service replied 1 year ago.

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Customer: replied 1 year ago.
tested fuse good. alternater is working fine. what next
Expert:  Toyota Service replied 1 year ago.

What is the output voltage of the alternator?

Customer: replied 1 year ago.
right around 14 volts
Expert:  Toyota Service replied 1 year ago.

Where are you measuring this voltage please?

Customer: replied 1 year ago.
Measuring going into battery
Expert:  Toyota Service replied 1 year ago.

If you are measuring 14 volts at the battery cables (battery connected), you are getting sufficient alternator output. You may not be getting the proper amperage output, but your voltage is correct. Note: on an alternator, when you remove the battery cables and the engine dies, you can easily cause damage to the internals of the alternator. What is the amp rating of this alternator?

Customer: replied 1 year ago.
130 amp alternater
Expert:  Toyota Service replied 1 year ago.

What are the symptoms? If you have a good 130 amp alternator, outputting this amperage, and you have 14 volts at the battery, it is charging properly.

Customer: replied 1 year ago.
Would not start one morning. I jumped battery properly and truck started. Took cables off and noticed amp meter was fluctuating between 6- 9 volts. Took battery out and had it tested at two places both said it was good. Being old school all that was left was alternater. Had that replaced and it acted the same. Battery is now dead
Expert:  Toyota Service replied 1 year ago.

Sounds more like you have a parasitic draw than a bad alternator. You have a 12 volt DC testlight?

Customer: replied 1 year ago.
I do
Customer: replied 1 year ago.
Actually can't find light. Can I use meter
Expert:  Toyota Service replied 1 year ago.

A light is better. Here is what I recommend: Charge the battery, 2 amps overnight, battery cables disconnected. Connect the cables and start it up. If it starts, shut it off and disconnect the negative cable from the battery post. Close all the doors. Clip your test light ground wire to the negative battery cable. Touch the pointy end to the negative battery post. If the light comes on bright, you have a parasitic draw. Pull fuses one at a time until the light goes out. when the light goes out, that is the circuit you need to investigate. Note that the light will come on bright when you open the door to get to the fuses under the dash.

Customer: replied 1 year ago.
Ok. Will put battery On charge tonight. Will go to auto store and pick up tester. Will do what u recommend tomorrow after work. How do check with you tomorrow. Also this truck has a external voltage regulater I believe. Could that be problem. I also don't understand draw theory because amp meter was fluctuating
Expert:  Toyota Service replied 1 year ago.

If the battery is low the gauge will fluctuate Reply to this chat box; I will reply as soon as the site sends me an alert of your posting

Expert:  Toyota Service replied 1 year ago.

As long as you are measuring 14 volts, we can rule out voltage regulators.

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