caper11

I noticed the last couple of weeks that after starting my truck in the morning that the voltage hangs at 12.5 after startup for about 10-15sec than rises quickly to 14volts, and doesnt do a post startup cycle. Sometimes the WTS light doen't come on, voltage hangs than rises quick, and goes through its post heat. Than today the WTS light came on, i waited for it to go out heard the click of the grid heaters shutting off, started the truck and the voltage hung 11 for about 10 sec than heard another click and the voltage went to 14v than went to a post heat cycle.
I never noticed this before, the voltage always rose to 14 after a start than did it's post heat if it wanted. ONLY does it in the firat start of the morning NO CEL and no code on the dash after doing the key trick. It almost seem the that grid heaters are coming on again after the engine starts to crank, even thought they went through the key on "wait to start" cycle.
Anybody else notice this senerio? I even had a voltmeter on seeing if it was a wonky dash voltmeter.

cbrahs

grid heater cycling. normal. these things pull a retarded amount of amperage. the grid heaters will cycle for a couple minutes unless driving over 15mph then they won't come back on unless needed after next start.

cbrahs

here is the description from Chrysler

Before replacing the alternator on 2006-2007 Ram trucks with a Cummins Turbo Diesel engine that is experiencing charging issues, please be sure the vehicle has the latest software found in TSB 18-001-07 which contains charging system software corrections/enhancements.


Note that in certain cold start situations it is normal for the voltmeter to fluctuate, the headlamps/interior lights to dim and/or the heater blower to slow down/fluctuate for approximately 3 minutes or if driving under approximately 18 MPH. This is due to the high power draw of the intake grid heaters and is not representative of a problem with the electrical system. Replacement of the alternator will not correct this normal characteristic. Please refer the customer to the "Starting and Operating" section of their owners manual where these normal operating characteristics are described in detail.

AH64ID

Sounds normal... are you watching from the dash?

The dash is what the ECM wants you to see, and is not an actual representation of voltage.

HMX-1

Yeah, don't watch the dash. My '08 shows 12 volts all the time but when I drop a good DVM on my batteries I get 14.3 volts while it's running.



-Kris