I replaced my alternator on my truck and it now surges between 13 to 16 volts, why?

Question

The guage goes up and back and the lights get brighter as the guage goes to the high mark. It has not gone past the top of the normal mark yet, but it could only be a matter of time.

Answer 1

Voltage regulator, but depending on if your vehicle (you didn't say, BTW) has an internal VR (most modern cars do ) you may have to change the whole alternator.

Answer 2

A: it could very well be the regulator as stated above, but if it is a inter-mint problem that happens in a regular interval then I would be looking in to the devices that have been added into the vehicle. One may have a ceramic breaker which when the device "shorts-out" will trip the breaker and disable it until the breaker cools off and it re-energizes the current, which of course will over heat the breaker yet again and shut it off till it cools and this will repeat it self.

the other thing..that could very well be is your battery has drooped a cell and will not complete come up to 13.5 volts (yes on a 12 volt system) and the alternator is just trying to do it job.

most new if not all of the new car from late 90's on, have the regulator built into the alternator.

check for a bad device.

replace the battery

then replace the voltage regulator/ alternator, with the oem recommended amp unit.

Answer 3

Start with the alternator, is it from Napa? I have seen a bad string of Napa alternators lately with the same issues! Most aftermarket alternators have a warranty on them that will cover free replacement if defective. Take it back and try a new one.

Answer 4

Thats because the problem is in the voltage regulator. replace it.

Answer 5

I've seen this happen when the voltage regulator is bad.