lights dim when started in the morning

[RRobine]

When I first start my truck in the morning, I notice that my interior and exterior lights shine bright then go dim for a second or two. This happens periodically while the truck is cold, then when she warms up everything seems to be find. Is this normal.

 

[gravedigger]

Mine does the same thing, another thing that happens is that the power window do not operat as fast and the heater will not blow with full force. I belive it is the ampage building up. That causes it. It is normal though.

 

[bmoeller]

On a cold engine, it is the grid heaters cycling on and off. There are 2 of them. They pull almost 100amps each. There is a sensor in the intake manifold that tells the ECM (or PCM whichever the case may be) to turn them on. Sometimes, if it is cold enough with the engine idling in the winter, the intake temp will drop enough, that they will cycle.

 

[RRobine]

Thanks for your responses, you saved me a trip to the shop.

 

[dcscott]

If you watch your panel voltmeter you will also discover that the alternator doesn't kick in until after the grid heaters are finished cycling on & off. This is to prevent the grid heaters from trying to suck excess amperage from the alternator and damaging it. Once the heaters are done you'll see the voltage come back up to normal because the alternator has now been told to wake up.

 

[evldsl]

I work for a airline and we call that shedding power, when something else needs more power another less important item is shed its power. Thus when your truck is turned on the truck sheds power to operate the most imporant equipment needed at startup and idle. Or perhaps its something else but with the way all these new type trucks use computers nowdays I wouldnt put it past the manufactures to save a few bucks and develop them this way.