Reader Question: Hi there,
My alternator is only charging at 10v. Now this is the third alternator in 12 months that has done this. I have had them replaced with refurbished ones each time.
I changed the battery as well to a deep cycle sealed but it still keeps killing alternators.
Would the brushes cause low voltage or is that more likely the diodes?
Any help would be greatly appreciated.
Is there an alternator rebuilder in your area you can take the car to for testing? You should be testing the alternator output AT the alternator not at the battery. If the alternator is outputting properly at the alternator but not making it to the battery, you probably have a wiring or ground issue in the wire harness.
I sometimes will make up my own set of cables to attach the alternator directly to the battery to eliminate any chance of broken or corroded wiring on the vehicle or with in the harness. An alternator shop can make these cables up for you if they do not already have them for sale.
If the alternator output on the alternator is 10Volts, there must be a problem with the brand of rebuilt alternators you are buying 3 alternators with the exact same problem is highly unlikely though so would look harder into wiring/grounding and connection issues.
A deep cycle marine type of battery is not what should be in a car. If that is what you have installed change it for a regular automotive battery.