alternator question.
#1
alternator question.
hey, so i have a 94 pick up 4x4 3VZ-E. my alternator started surging the other day and then died while i was on the highway. Ive replaced the alternator with a used but great condition alternator off my parts engine. all seems well except that the e-break light and the battery light are now on. i know this is to do with the alternator but does anyone have any ideas why its staying on? should i be getting my new used alternator and battery tested to see if there is any issues?
thanks for the input.
thanks for the input.
#3
Registered User
This is from another post that I wrote about a month ago.
If your brake and alt lights are staying on, your alternator doesn't seem to be charging.
You should probably get it tested.
About alternators...when the key is the run or start position and the engine isn't running your alternator light and your brake light are both on, if you have access to the wiring diagrams, here's how it works. The brake light is only supposed to be on when either your emergency brake is on or your fluid is low in the master cylinder...so what's going on? The alternator light is fed from the brake light circuit through a diode to the alternator. When the alternator isn't charging it is a dead short to ground, so the brake light and the alternator both light up. The alternator requires an exciter voltage/current in order to start charging, this is provided by means of this alt/brake light circuit which is fed from the 15A engine fuse. Once the engine is started and the alternator is turning because it is excited it will start charging against the feed from the alt/brake light circuit, but because there is a diode in the circuit, the alt cannot back feed this circuit and because the alt is now charging there is no path to ground for the alt/ brake light circuit and the lights go out.
You should probably get it tested.
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09-20-2015 09:00 AM