alternator output??

[captainlewis]

I have a good battery, I have tested it. After the car sits the voltage is 12.5 at the battery. I hook a voltmeter to the battery and start the car the voltage at the battery only goes up to 13.6 volts, with no accessories or lights on. I rev the engine to 4000 rpm the voltage stays constant at 13.6 vlt. After a long drive I pull over and test it at 4000 rpm 13.6 vlt. Is there anything else that could cause this voltage to below 14.4 at 4000 rpm besides the alternator, Thanks JL

[dreddy]

Hey captain. I don't have a certain answer for you but you posted an alternator problem about 3 minutes after I did. Do some regulators simply not allow the standard 14.4? As long as it is north of 12 it may not be a problem as long as it continues to charge. Are there any other symptoms or problems?

Good luck.

[Formerly Steve Wilkinson]

Absolutely identical to the numbers I get on my '83, new alternator, good battery.

[911pcars]

Try measuring the alternator output with some load on the electrical system (e.g. high beams and heater fan). If the alternator can't produce enough power for these accessories as well as enough to charge the battery, the system is working on a deficit and the battery will eventually die. Under the above conditions, 13.5 - 14.5 volts should be within spec.

The red charge light will also indicate a charge/discharge condition. You'll want a sufficient electrical cushion for other accessories you might use concurrently (e.g. defroster, wipers, power windows, audio system, etc.).

Sherwood

[dshepp806]

Those numbers look similar to what I see, as well. As 911pcars noted, load it heavily just to check.

Best,

Doyle