Do I need to replace my alternator?
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Do I need to replace my alternator?
I drive an '88 Bronco, it's a 5.0 and it's fuel injected, anyways starting a couple days ago usually in the mornings during the first start up of the day, it keeps dieing on me, and when I have headlights on, when I go to start it the headlights dim, and when it is about to die and i have the cab lights on they dim when the idle rises up and falls with the rpm gauge. Do I need to replace my alternator, or is it something else? That is the only thing I can think of.
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From: Bixby, OK
First off welcome to FTE, and secondly, have you posted in Electrical? They might be able to help ya out a little bit too. But from what I can tell, you say it starts up then dies? That usually doesn't have to deal with alternator. And then whenever you go to start it back up, your battery is still a little tired from the first start, and if you have the headlights on, they're deffinately going to dim. The starter pulls most the juice from the battery, and doesn't like to give it to your headlights. So that's the explanation on that, from what I can tell, it's not the alternator. Maybe your battery needs to be replaced since it looks like when the cab lights go up and down with the idle, the lights are pulling their power directly from the alternator. Now if you just have your cab lights on and you rev your engine, they will get brighter, but within the idle.. I don't think that is supposed to happen.
Logistics Pro
Joined: Apr 2004
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From: NJ where fun comes to die
Don't spend money replacing parts with a guess. You can have alternators, starters, and batteries etc. tested at your local Pep Boys, Auto Zone, Advanced Auto stores, or maybe Napa. Also pick up an inexpensive multi meter so you can do some of your own testing. I second on the electrical forum. Franklin and those guys are pretty good.
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Originally Posted by phatpony
Could be as simple as a bad regulator. Just have one of those stores mentioned hook it up to have it checked out. good luck
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Originally Posted by RomerB2
14.2? That's kind of high isn't it?
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Originally Posted by RomerB2
For a high output alternator. Don't most alternators run something like 12.8 or lower?
Logistics Pro
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From: NJ where fun comes to die
Most systems will charge at about 13 to 14.5. Less is not good and more is not good. Less won't keep up with the charge needed and more will fry things. The alternator produces the current and the regulator "regulates" how much should go out to the system, depending on what is being used. I believe it also changes the kind of current produced into something useable. Though the systems are 12 volts, when you check a fully charged battery it will probably read around 12.25 to 12.75.
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The regulator, which can be separate or internal, tells the alternator how much to put out, voltage wise. The alternator delivers current, within its rating, necessary to keep up the voltage. The AC to DC conversion takes place within the alternator using diodes, usually as diode assemblies. The alternator may not have enough output if it turning too slowly, like at idle. Thus the rev up test to see if voltage raises when the engine fast idles.
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From: arizona
Trike1946...I took your advice and ran my little '56 over to Checkers for an electirical system test. The battery light started glowing the other day.They isolated the problem to my generator so it saved me a bunch of hassle. The extra time and money they saved me can now be squandered on something else important...like new battery cables or...?
Thanks, Doug
Thanks, Doug