I have a strange issue with my alternator. when i start up, the volt gauge takes about 4 seconds to come up to the normal 14 volts. the starter turns much slower than usual but it still starts. the truck runs and drives ok except for those issues. Occasionally it will throw a code for the alternator field circuit not switching properly. I am wondering if the alternator is borderline and beginning to fail or possibly one or both of the batteries are failing. it cant be the grid heaters because it's 109 degrees here.

 

First thing i would do to test it would be disconnect the batteries and see if it has a hard time idling.

 

you pull the alternator and take it to an auto parts store and have it tested..

on the truck.. use a volt meter to measure the voltage the dash gauge is computer controlled..like the rest of the gauges.

or do what did..I tried to clean the connectors and broke the output stud..then broke on the cover studs...time for a new alternators..it fixed the tranny hunting problem. so I was happy in the end.

-dkenny

 

mine takes a long time to reach voltage, you probably have marginal batteries. need a load test to be sure. Alt is probably ok ED

 

Test batteries individually by disconnecting the pass side bat. Replace both if one fails. Use the good one for lawn mower or whatever. The old one will pull the new one down. Clean all heavy electical connections.

 

Go to a shop [ because the "best" tools , a charging / starting with a load tester will cost too much ] and with out you could miss many things .
The 1st thing that occurred to me by your description , was , that the brushes are worn in the alternator .

 

You shouldn't need to remove to test....most auto parts stores will "load test" the alt while on the vehicle and running.