How do you get it tested? Do they just check the voltage when the car is running, or do they actually test the alternator? Cause I can check my own voltage thank you...
If I've got like everything on and I'm sitting there idling my car will dip down to about 10 volts and my headlights and stuff dim a little...would replacing the alt with a higher amp alt solve this?
To test an alternator, it is tested with the car on at both idle and above 2k RPMS. Your voltage should NEVER drop down to 10. Something is wrong with that picture. Think about it. The battery alone has 12....Originally Posted by Tinton
Anyway, usually the procedure goes a little like this:
1. Someone hooks up some leads onto your battery.
2. You check the battery first. If it's good, then the alternator gets checked.
3. The car is running at idle. Depending on the tester, manual or electronic, it takes a reading of voltage at idle.
4. Car then gets rev'd up to above 2k RPMS and held there steady, not revving up and down...steady. Another reading is taken. That reading usually puts a load on the battery and then it subsides.
5. Results come out.
Rule of thumb is this:
After a car is up to operating temp, your voltage at idle should not drop below 13.0-13.3V. Above idle, same scenario, your voltage will jump up somewhere past 14V and stay there based on RPMS and load. What AMPS the alternator puts out is all a function of a combination of RPMS and internal construction. "High output" alternators are notoriously finicky. Some work better than others. Some are nothing more than a smaller pulley on a stock alternator (makes it rev a lot higher and thereby sometimes putting out more amps). Some are the real deal. Usually the price will be an indicator of which one you have. Bottomline is that you only need a "high output" alternator IF you have the load that needs it. Big stereo systems, hydraulics, lighting, etc. Some cars already come with larger output alternators from factory too.
Hope this helps.
I still think it's the alternator BTW.
Thing is, the car has ALWAYS been like this. I've changed the battery once like a year ago, and the alternator doesn't seem to be going bad because it always has the same amount of volts. Like, when I go to start it in the morning it'll be at like 10 volts. Idling with no accessories on it'll be right at 12v. If I rev it up it goes to like 13. Load I put on it though makes it go much lower. I always thought it was because the car is ancient and it probably has bad grounds and maybe a short.To test an alternator, it is tested with the car on at both idle and above 2k RPMS. Your voltage should NEVER drop down to 10. Something is wrong with that picture. Think about it. The battery alone has 12....
Anyway, usually the procedure goes a little like this:
1. Someone hooks up some leads onto your battery.
2. You check the battery first. If it's good, then the alternator gets checked.
3. The car is running at idle. Depending on the tester, manual or electronic, it takes a reading of voltage at idle.
4. Car then gets rev'd up to above 2k RPMS and held there steady, not revving up and down...steady. Another reading is taken. That reading usually puts a load on the battery and then it subsides.
5. Results come out.
Rule of thumb is this:
After a car is up to operating temp, your voltage at idle should not drop below 13.0-13.3V. Above idle, same scenario, your voltage will jump up somewhere past 14V and stay there based on RPMS and load. What AMPS the alternator puts out is all a function of a combination of RPMS and internal construction. "High output" alternators are notoriously finicky. Some work better than others. Some are nothing more than a smaller pulley on a stock alternator (makes it rev a lot higher and thereby sometimes putting out more amps). Some are the real deal. Usually the price will be an indicator of which one you have. Bottomline is that you only need a "high output" alternator IF you have the load that needs it. Big stereo systems, hydraulics, lighting, etc. Some cars already come with larger output alternators from factory too.
Hope this helps.
I still think it's the alternator BTW.
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