Engine/Transmission (1998.5 - 2002) Question about lights dimming when cold

[DirtyDodge]

Hi,

I know this is a normal thing to happen, just curious what it is and why it does it. When the truck is first started cold, the lights will dim for a second then go bright again. This happens several times in the cycle before it stops. My old 92 CTD did the same thing. Its like a switch or solenoid or something that is drawing extra current for a short period of time.

Derek B.

 

[ChillyDog]

That would be the grid heaters cycling on and off too warm up the air coming into the engine.

 

[DLausche]

My 99 does this too. I always regarded this is normal. The only thing I question is why it also does this after I start it when the engine is already warm. I usually shut down when doing the McD's drive-thru in the morning. The grid heaters appear to start the on-off cycle all over when I restart. The engine is fully warmed up at that point. Is this normal?



-Deon

 

[Shovelhead]

Here's the why:

Instead of using Glow Plugs like the Fords & Chevys, the Cummins uses 2 grid heaters in the intake tract to preheat the incoming air, each pulling 95 amps for a total of 190 amps! At 12 volts, that's nearly 2300 watts, one whopping load on the battery!



After the engine is warm they should cycle for a much shorter time on start-ups.

 

[Dkevdog]

Don't know about the rest of you who have FP gauges, but When it the grid heaters cycle I even see a 1psi reduction in my fuel pressure. I guess its pulling enough voltage away from the pump to drop it !



Kev

 

[krs]

Keep your eye on that system because it can result in dead batteries at best and engine fires at worst. Here's how it's supposed to work:

http://dodgeram.org/tech/dsl/FAQ/cold_wx.htm

 

[DirtyDodge]

Thanks for the input guys. Learn something everytime I sign in to the TDR.

Derek B.

 

[parcher]

Once you get over approx 15 mph the grid heaters will no longer cycle, at leaast that's how my '02 works.

 

[illflem]

If I leave my block heater plugged in all the night the grids don't cycle at all before starting, but if it's 10-20° below zero they will start cycling any time I go slower than 15 mph for quite some time. It's just that the intake sensor is still seeing temps below 59°.



I also have an intake temp gauge, the temp after the block heater is plugged in for just four hours is usually in the 70s no matter how cold it is outside.

 

[monkeyman]

Grid Heaters Cycling

I got sick of my lights dimming at stoplights due to the Grid heaters cycling on and off, they draw lots of amps. PSdieselproducts sells an adapter that prevents them from going on if the water temp is over a certain limit. After doing the install about six months ago the problem has never surfaced again.

Hope this helps.

Rick