I have a '97 F250 w/ 7.3L...can't keep batts charged. Interior lights stay on so I pulled the fuse, batt still discharges. Altenator puts out 12volts. Bad relays? Bad volt regulator? Other issues will post later...electrical is the biggist problem..
Confused in Mich...
I see I posted this in the wrong area (goes to the confused part) but any help will be accepted.

 

A moderator will move you to the right section, but any 12 volt system I know of, the alternator output should be at least 13.9 and up to 14.5 volts. Pull the alternator and have it checked out. Newer units have the regulators built into the alternator. Good luck!

 

Do you know if lack of voltage will cause other problems, ie: lights staying on (door switch), gauges being goofy, heater fan not working right? Seems like gremlins running through the whole thing..

 

If it was an IDI we could probably help you BUT the systems are totally different as is the wiring....... sorry!!!!!!

 

Brandstruck,
Welcome to FTE and the IDI diesel forum.

Moved post to the 1994.5 thru 1997 Power Stroke forum.
The guys up there will be much better able to help with your truck.

 

Take your truck to an auto parts store, (NAPA Advance, Auto Zone, Oreilley's, etc.). Have them do an electrical load test on your alternator and electrical system (they do this with the alternator in the truck with it off and with it running both with and without a load.

Interior light staying on, one of two things 1. bad door jam switch or switches (replace switch) 2. bad headlight control switch (replace switch) Fuse to interior light also controls your odometer along with other items.

 

You need to disconnect your batteries when they are fully charged and have them load tested individually. The batteries should be able to hold 800-1000 cold cranking amps if they are any good. Without knowing this information, you can't really go any further. A voltmeter will not help you at all. You need to know how many amps that these batteries can maintain for a minute or so.

If the batteries pass the load test, then hook up the load tester to both batteries and start up the truck. Make sure that the charging circuit voltage reaches at least 13.5 volts. The charging voltage will always be slightly higher than the battery voltage.

If this works then you will have to find the short that is draining your batteries. Start by disconnecting your batteries and then put a lightbulb in series with a battery, so the battery will be powering the truck thru the lightbulb. If the lightbulb comes on, then remove your fuses and replace them one by one until you find which circuit is drawing the power.

On rare occasion, I have seen batteries that will self discharge themselves internally but this is very rare and easily determined by leaving the batteries disconnected and load testing them a day later. I hope that this helps... Good luck.

 

New altenator seems to have fixed most of my issues, $252.00 at NAPA. 14.35 volts now. Thanks for everybodies help.Took me longer to find my socket set than to replace the alt. I think I messed something up, ABS light stays on....