wacky voltmeter

[uncle t]

Been a month now trying to get help with reason my duramax has refused to turn off on three occasions. More Power, adminstrator of member's forum suggested one cause could be faulty alternator. I started monitoring voltmeter. When I turn the key to on position, voltmeter reads 12.5 V. Once started it stays at 12.5V for about 30 seconds, then kicks up to 14- 14.5V Stays there forever after that, until next cold start up. Never paid attention to it at startup before. Is it normal?

[YZF1R]

Yes, it's normal. There is a heater grid in the intake to help initial warm up on cold starts. As soon as the heater turns off, up go the volts to normal.

Steve

[Joe.G]

Yes, it should dip quite low and stay there until the heaters turn off, then it should jump to 14 volts +. I'd say that mine on a cold start in the morning it takes 30 to 35 seconds before the engine heaters turn off and that's at 78 to 80 degrees here. Well, come to think of it it does the same thing in the winter when it's 30 degrees in the morning. I don't think that is the problem.

[letsgo]

Didnt believe that the alternator didnt kick in right away, did a test this morning

batteries sat at 12.58v ignition key off.
turn key for cranking voltage, drops to 11.86v.
motor running start counting 1001 1002 etc.
voltage didnt increase until 1030.
after 30 seconds voltage jumped from 11.9v to a full 14.58v.
why I dont know???
your shut down problem, cant help.

good luck

GMC 2002 DURAMAX SLT EXCAB SHORT BOX 2500HD 4X4 AUTO

[ 08-09-2002: Message edited by: letsgo ]</p>