Posted by a p bloom on Tuesday, March 09, 2004 at 0:14AM :
In Reply to: Wiring Relay posted by Josh on Monday, March 08, 2004 at 10:28PM :
There is no way to wire a relay to relieve the load on an alternator. The battery and alternator, when the engine is running, act as a team. The battery supplies electricity, and the alternator replenishes it. When the engine is not running, the battery is the only supply of electricity. The alternator is designed to keep the battery charged even when all the stuff in the truck is turned on.
The exception to that statement is a truck with an electric-over-hydraulic snow plow, or some large equipment like that. The stock alternator in that case may have a hard job keeping up.
If your alternators are failing, it is probably because you are buying shoddy merchandise. I have spoken on this subject before. The re-manufacturers of alternators use quick and dirty methods to "rebuild" the products.
Here's a way to start, and I stress START testing the vehicle to see what's going on:
You must first understand how an ammeter works. It measures the amount of current (measured in amps) that an accessory uses. You wire the ammeter in series with either lead (positive or negative) of the accessory. Like this:
+ ...... M ......stereo....... -
The "M" in the above diagram is the ammeter. The meter is inserted in the positive lead going to the stereo. With a normal stereo, as you said, without any fancy amplifiers, etc, I doubt that it would draw more than 20 amps, but I could be wrong. What size fuse is feeding the stereo? It can't draw more amperage than the fuse is rated. An alternator would certainly be able to supply that much - it's less than the headlights draw.
Think of this: how many trucks have stereos, and how many people think their stereos are killing their alternators? You are the first I've heard of. Try riding around for a week with the tunes turned off. (Easier said than done, of course !!!) See if the alternator survives the test.
There may be something else going on that is doing it. You must be sure that ALL connections are clean and tight. This includes the battery terminals, alternator terminals, and the plug that goes into the voltage regulator. Is there a voltage regulator on the firewall? Unscrew it and clean the area where the mounting screws go, then remount it. Have you replaced it when you replaced the alternator? It may be at fault. The easiest thing is to get a new one. They are cheaper than alternators.
You must also measure the voltage coming out of the alternator, with the engine running. It should be between 13.2 and 13.8, roughly.
You should get a Radio Shack digital voltmeter to do this test. They are inexpensive.
I will be away for a day or two, but if you wish to contact me directly by email, please feel free to do so. I can perhaps help you walk thru the steps as you do them.
Arthur P Bloom
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