electrical question.. help needed please

[1971short4X4]

I hate to write a book here.. but i would really appreciate some help with this.

First...I am using the stock external volt regulator setup.

My truck battery reads 12.2 volts (with the engine not running). with the engine running (at roughly an 800 RPM idle) the voltage at the battery is about 12.4 volts. the problem is my stereo equipment needs between 13 and 14.5 volts to operate properly.

I tested my daily driver honda and with the car off the battery has 12.2 volts like the truck BUT while idling the car has 13.8-14.0 volts (the voltage does not vary much at all .. no matter how much you rev the engine)

While back at the truck.. the voltage varies up to about a max of 12.8 volts as you rev the moter up. I think this is low.. but hell maybe the trucks really weren't designed to have more??

I initially thougtht that the problem was a bad regulator... but i put a new one in and the voltage with the vehicle running is still between 12.2 and 12.8 volts.

the question is what is the best thing is for me to do to get my voltage within the 13.0-14.0 volt range. In order to determine this i need your help to see if my truck is normal or not.

It would be really helpful if a couple of you could take 2 measurements for me. a) what your battery voltage is with the vehicle off B) what your battery voltage is with the vehicle ideling.c) please also let me know if you are running the external regulator or if you have converted to an internal regulator.

I know this is a pain .. but any help would be appreciated and help me figure out what my problem is.

[OhioDan]

How many amp alternater do ya have. You're probably using about a 55 amp right now. Try a alternater with a higher amp output. Not sure what sizes they have available? JMO

[Patrick Sullivan]

I don't think you've got a problem. They didn't have 1000 watt stereo systems in 1971, they had AM radios with 1 speaker. 12 volts was about what these things needed. You're trying to run modern equipment on an old alternator.. :p

Some of the old regulators had a setting on the inside, where you could change the operating voltage. I don't know if yours has that, or how you would go about changing it.

My recommendation would be to switch over to a nice 100-140 amp internally regulated alternator. Chrome, of course.

[Gordo]

The system you have is capable of maintaining 13.8 to 14.2 volts depending on the reg adjustment, assuming the alt is in good working order and batt is fully charged (12.6 V). FOR TESTING PURPOSES ONLY, unplug the connector from the reg and connect a jumper wire from the connector "F" terminal to the connector "Bat" terminal. Attach your voltmeter to the batt. posts and start engine ONLY long enough to get a voltage reading. This will by-pass the reg and allow alt to produce it's maximum output. If the alt is in good working order you should get a progressive reading of more than 16-17 volts. If it doesn't give you a good reading the alt is not working to it's full potential, replace it/rebuild it. The reg adjustment should not be necessary if it's new and no one has messed with it. My guess would be your alt is at fault.

[Yellow Cheyenne]

Gordo is correct. If you aren't comfortable with the testing procedure, take the altenator to about any auto parts store. They should be able to tell you the voltage and amperage that it is putting out. There usually is no fee for testing the altenators. From there, even if the altenator is at full charge, it won't be able to handle a huge load if it is the stock unit. When you are testing the battery voltage, turn your stereo off and any other source of current drain. Start the pickup and bump the RPM up a little above idle. If the voltage goes to 13.8-14.0 volts with no load, but won't maintain the voltage when you start to turning power on to your equipment, that says the altenator is not capable of putting out the current you need. Get a newer, heavier duty unit.