On startup the car registers 14.4v (via multimeter). Once I start driving around the voltage creeps down eventually leading to the car to stop running. At this point the car will not turn over or start. It will however start via jumper cables.

Tried 2 battery's, new battery bolts, 1 new alternator & the problem remains.

Any ideas?

 

check the small wire going to the alternator to see if it still has 12 volts on it when the problem occurs.

 

Tried connecting another wire from 12v positive to back bolt of alternator. Problem remains.

 

I am having the same problem. New alternator...no change, new PCM...no change.
The small red wire only has 10.4 volts the larger one connected to the battery has "battery voltage" 12.57v engine off.
All connections cleaned and tightened...no change.
Autozone tested in car...30 amp out put only.
Measured voltage = 13.9v with nothing on....12.4v with lights and fan running.

 

90 rocz, start your own thread

Ws, take your alternator to be tested but also take a hair dryer with you to heat the crap out the alternator.

The only things that could make the alternator put out less and less over time is the alternator itself or the loads on the alternator are increasing, or it's wiring is increasing in resistance.

So measure the output from the case of the alternator to the large output post. If it's low and the small wire going to the "L" terminal has the correct 12 volts, the alternator has to be the problem.

If it's one of the cheapies like a "duralast" or others similar, sorry. They are the worst and wouldn't surprise me if it was DOA.

 

Also look for bad grounds and corroded cables. Run an extra wire from the battery (-) straight to the alternator case for a test and see if that helps (use at least a 10 ga wire or larger).

 

What I don't understand is on start up It shows 14.5V. After it's running for 10-15min the voltage creeps down.