Grid Heaters

[SHobbs]

Do the grid heaters in the 4th gens act the same as in the older generations? After starting the truck the amperage gauge does not fluctuate nor is there is a difference in the engine sound like my second gen. did. I have been turning on the exhaust brake to help with the warm up, not sure if that deactivates the heaters or not. If they are working they are not noticeable at all.



Thanks,

Scott

 

[Hoefler]

A Lot depends on ambient temperature and block temperature. if not cold enough it won't cycle.

 

[SHobbs]

Morning temperatures were in the 30's.

 

[goodguys75]

you will know when it kicks on... . the volt meter should be fluctuating like crazy and the lights should dim when on for a few until it kicks off... . dont think there is a charging system in the world, that would keep up with that much draw.....

 

[Hoefler]

If the block has residual heat from the last time it was running, the heater may not come on at all, regardless of outside air temperature.

 

[Alan Reagan]

I believe they made a software change in the ECM that stops the fluctuation of the meter. Many drivers weren't sure what was going on so Dodge "fixed it" so that the meter reads a steady voltage. You will find the same is true with the oil pressure. It typically reads one value at idle but almost as soon as you come off idle it will rise and remain steady even with speed changes.

 

[Cummins12V98]

I believe they made a software change in the ECM that stops the fluctuation of the meter. Many drivers weren't sure what was going on so Dodge "fixed it" so that the meter reads a steady voltage. You will find the same is true with the oil pressure. It typically reads one value at idle but almost as soon as you come off idle it will rise and remain steady even with speed changes.

Oil pressure in 6th at 60 as 45psi and same speed in 5th is 49 psi. These are towing numbers on the EVIC. The gague on the dash shows the same info.

 

[Alan Reagan]

Cummins 12V98, I just checked my oil pressure guage. With 0 40 and 110 being the only known checkpoints on the guage, I could barely see mine move when I downshifted. The EVIC was as you described. But as soon as I come off idle, the gauge itself moves right up to just over 40 and sits there thru the gear changes to 6th gear. I hit the downshift button and the EVIC immediately went to 50 and then dropped to 47. The gauge movement itself was neglible to me.



On the voltage gauge, This is what one of the older Originally Posted by 2003 Service Manual:



On vehicles equipped with the optional diesel engine, the ECM is programmed to restrict the voltage gauge needle to a position above the graduation on the far left end of the gauge scale and suppress the check engine indicator operation until after the engine intake manifold air heater has completed a pre-heat or post-heat cycle.



So as early as 2003, software was being used to control the gauges in the instrument cluster.



I don't have a new service manual but my understanding is, on the voltmeter, that the fluctuations in the voltage guage were further limited until the end of the post heat cycle because so many people thought something was going wrong when the grid heaters were cycling. Now it's been a while since last winter here in Georgia, but I seem to remember that mine does not fluctuate like my 1998 and 2001 trucks did. I seem to remember that I get a little headlight dimming but the voltage guage fluctuations are minor.

 

[SHobbs]

Alan,

That is what I was looking for, I could not tell if the darn things were actually functioning.

 

[Alan Reagan]

Sorry if I digressed. If you want to check the actual grids, the resistance should be in the . 1 to 2 ohm range. Usually the resistance is about . 1.



When you turn the key on when it's below 50, if your door is open, you can usually hear the grid heater solenoid and relays engage. If it is dark and the heaters are cycling, you might notice the lights dim for a couple of seconds and then return to normal. You may even see a slight fluctuation on the voltmeter of maybe a volt or two but not the wide fluctuations that the older trucks have. My '98 would drop to about 10 volts during a cycle.



If it is starting good on cold mornings, my guess is they are working just fine.