Alternator keeps needing to be replaced. Any ideas why?

I had a problem with both the speedometer and odometer in a Lincoln. It may also have an effect on the engine operation. My speedometer showed 45mph standing still and miles were rolling up on the odometer.

For me, it was a bad Alternator. The alternator was shorting out through the case. You should have your alternator checked and if you find out it is good, then the problem is something that is charging the car body.

You are getting a stray current that is messing up your dash and engine controls. You may have a power wire which rubbed through its insulation.

you can buy haynes repair manual at auto zone or advance auto parts store and look at the electrical diagram to alternator and starter.

check voltage regulator, it may b faulty, also sheck all wiring

My sister just finally passed inspection with her 2002 Elantra. Same exact problem and the sensor was replaced twice. Here's what you need to do. I know it doesn't make sense but I found it in a tech bulletin. You need to remove the alternator bracket that connects to the block as well as the engine ground and body grounds near the battery. Clean them off with a wire brush and also clean off where they connect to the body of the car. Reconnect them and clear the engine light. My sister's finally passed after that. It did not pass for 2 years until this was done.

It could be one of 3 things.

1) Your alternator belt is loose and so your battery isn't charging properly

2) Your battery is dead, needs replacing.

3) Your alternator is faulty and needs repair/replacing.

As its most likely to be 1 or 2, especially if you battery is more than 2 years old. I'd go to a garage/battery shop and ask them to check it. More than likely with a view to replacement.

probably one of the easiest waterpumps in existence to remove-drain coolant, remove serpentine belt, remove alternator, pump is just below the alternator-takes less than 1/2 hour.

You need now to look at the idler, (guide) or tensioner pulleys. Not sure which series you have or the year. The 5 series back to '89 has 2 tensioners and 1 guide or idler. The 7 series back to '86 uses the same. The 8 series back to '91 also has 2 tensioners and the 1 guide pulley Check these other pulleys for free spinning bearings.

ITS EITHER ALTERNATOR OR ALTERNATOR WIRES BROKEN OR DAMAGED.IF ALTERNATOR WIRES LOOKS OKAY.I WOULD REPLACE ALTERNATOR AND BATTERY CABLES.WHEN BATTERY LIGHT COMES ON ALTERNATOR IS NOT CHARGING BATTERY.REPLACING BATTERY TWICE A YEAR IS CHARGING PROBLEM.ALTERNATOR NOT DOING ITS JOB.IF YOU BUY ANOTHER ALTERNATOR BUY CORRECT AMP ALTERNATOR BUY WHAT FACTORY PUT IN.

take the negative side of the battery off and then remove the drive belt and there should be a belt tensioner near the belt take the pressure of the belt by using the 3/8 or a 1/2 in sockets and make sure you use the right side socket if needed

If the alternator you installed was rebuilt, it may not have been right from the beginning.
There are high powered diodes used in them to rectify the alternating voltage produced to supply the DC the car needs.
These can fail quickly and without warning.
It is possible that a defective battery could cause this failure so a shorted battery could have caused both the original and replacement alternator to fail.
If you are in the US, you can visit about any of the chain auto parts stores and they will test your alternator free of charge but call first to check if your local store offers this.

If the regulator for the alternator is separate; some are, some aren't, this should also be tested if separate and is not that costly to replace.