Just had alternator rebuilt Monday and worked fine for couple of days. Yesterday when I started truck the check gauges light came on and I noticed voltmeted wasn't coming up. After about 30 secs it came up to 14v. This morning same thing and I noticed torque converter lock up problem until I drove about 15 miles then it stopped. Had alternator redone but still same problem. Batteries load test good. Alternator plug is tight. Any ideas?

Sounds like crank sensor but cant remember if thats what the pcm uses to excite alternator

Might have the alternator re-tested for AC noise output.

 

Double check for P0336 error codes for the crank sensor if the tach is not reading or incorrect then the transmission will shift funny and alternator charging will be affected.

Also, the low voltage might be the grid heaters coming on.

Ed

Also, the low voltage might be the grid heaters coming on.Ed

Good possibility. Temp dropped down here when this started is that normal?

Grids draw major amps but shouldnt drop it enough to cause the check gauges

Edited April 18, 201411 yr by mopartechnician

some of the 99's had battery temp sensors under each battery. If they short out they will not let the alternator charge either, but I would start with the alternator.

some of the 99's had battery temp sensors under each battery. If they short out they will not let the alternator charge either, but I would start with the alternator.

 

You still should have a error code for battery temp sensor.

My truck does this same thing when I first start it in the cold.  The check guages light will remain on for 15 seconds or so and as soon as the voltmeter comes up it goes away.  i have always attributed it to the grid heaters.  Just my 2 cents.

My truck does this same thing when I first start it in the cold.  The check guages light will remain on for 15 seconds or so and as soon as the voltmeter comes up it goes away.  i have always attributed it to the grid heaters.  Just my 2 cents.

 

Actually that's a sign of weak batteries or bad cables. In other words the voltage is dropping off quickly and causing the low volt warning. Normally with strong batteries and good cables this will never happen. So time to do a voltage drop test and battery load test.