I've had my '03 HO 3500 for 6 years (bought at 110k; now has 158k), and it always bothered me that my voltmeter shows about 13v before and after engine start, and takes about 2 minutes before the voltage jumps up to about 14.8v on the gauge?

It's done it since I bought the truck, so I guess (?) it's normal, but I'd like to know why.

It does it if it's the first start of the day, or when the engine is warm.

I actually measured the battery voltage yesterday after start, but before the instrument panel meter rose, and it was showing 14.4 volts (instr panel meter showing about 13v), so I gather the alternator is charging right away after the engine is running, so why does the panel meter take so long to respond?

I have a diesel tech who owns an '04 and he said his does the same thing (says it's controlled by the PCM) so I shouldn't worry about it (I was thinking maybe it was time for a new alternator), but I am curious...

Normal? If normal, what's it doing/why?

 

Heater grid cycling on and off

 

Not any more-

I disconnected the fusible link at the battery yesterday.

Meter acts the SAME

 

I agree, it isn't the heater. Mine does the same thing and I can tell when the heater comes on and goes off by the dimming of the dash lights.

-Bob