a_reyes1014

iTrader: (1)

ok the car is running decent but now im seeing a voltage spike that dips low or spikes high. what could cause these voltage spikes?

Aaron Cake

iTrader: (1)

There could be a number of causes. Bad grounds would be the first one I would check, then a loose battery connection.

Where are you seeing the spikes? On a datalog?

a_reyes1014

iTrader: (1)

yes on the datalog the blips for a brief second then voltage goes back to normal

2Lucky2tha7

iTrader: (3)

I have personally come across this twice. In my car (eventually and over time -- about 2 years), and in my brother's car. I noticed these spikes in my datalogs steadily get worse over time. It started out around a 1.5 voltage spike or dip but is now around a 3V dip or spike. My brother's is the worst with 6V dips and spikes! I have finally sourced it to be from the alternator in both cases. The internal diodes eventually went bad in both alternators. It's definitely not the grounds or the battery cables, because the setups in both cars is more than adequate (overkill w/ 4 gauge wires creating a chain from the top of both rotor housings, the firewall, the ground connection on the strut tower,and then to the battery) and the MS grounds and power source are all hooked up securely and correctly.

a_reyes1014

iTrader: (1)

i have been debating to get my alternator rebuilt for more amperage. its pretty old. when the fan kicks on it drops a whole volt from 13.5 to 12.5. i will try that next. thanks guys for the help. i will keep you guys updated.