Voltmeter fluctuating
 

Occasionally when I start the truck the voltage is a little sluggish to come up to 14v. Sometimes I notice it comes up to around 12 then back 9-10 or so, then it will level back out to normal (14). Anyone else had this problem? I noticed the alternator sure looks small on these trucks.

I believe you are just seeing the grid heaters pullin juice...........normal

yep like whit said does it only do it below like 50 degrees?

Hmm, that is a possibility- I will keep an eye on the ambient temp when I see this happening.

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BTW

Stupid question here, but what is a grid heater? My Rover diesel damn sure doesn't have them.

mine is doing that and i checked coads and nothing came up but when i had it hooked to a snap on scan tool with the chrysler program it came up with bad dieodes in the alternater and thats causing it on mine. pluse the heater when its cold hurts it too
:c:

the grid heater is a series of metal strips in the intake that heat up REALLY hot by basically shorting the battery to ground through the strips, this is the reason the battery voltage drops, this helps the engine warm up faster and on really cold mornings start easier. Cummins motors don't have glow plugs, they rely entirely on having enough compression to ignite the diesel even when cold. the grid heaters will also quit cycling on and off once you reach 25MPH IIRC

my 12v will crank with the first turn of the key, it only gets in the 30's here in South GA but i never have to crank it twice cause it wouldn't crank the first time. the guy i work with has a 99 chevy 3500 with the 6.5 and it WILL NOT crank unless you let the glow plugs cycle completely, the motor can be at operating temperature and the ambient air temp can be 100* and it will spin and spin and spin till you stop and let the plugs cycle and then it will bust right off.....

I assume that the grid will heat up with out showing anything on the dash, correct? I have had the same problem with my truck, but it always levels out after a while. It's been down to -12C here (14F)

Ah I see. Yeah I realize now I have not seen any glow plugs in the engine.

it will say wait to start when you first turn the key on and after that it dosen't iluminate until the key is turned off and back on again or if there is an issue with the IAT sensor.

the only clue you will have that they are on will be your head lights dimming and the voltmeter dropping to a lower voltage and the sound of the engine will change as it is putting a HUGE load on the alternator when it cycles and loads the motor down.

In my case it may be a little more severe than normal as someone installed two different size, different age batteries in it.