Engine/Transmission (1998.5 - 2002) grid heater cycles too much?

[JEastbourn]

When I start my truck after it sits overnight and it is cold outside, the grid heater will cycle and pull the volt gauge down to about 9 and dim the headlights about 5-10 times. If I drive a while the truck warms up and everything is normal. Just wondering if there is a problem or if this is normal? Thanks.

 

[foolkiller]

my 99 did this too. i never figured out if it was normal but disconnected the grids anyway after seeing pics of the kind of damage that can result from grids that don't shut off..... very scary.



the pics are in a thread here on tdr somewhere.



i live in sandiego so i had no problems with cold starts. i took a couple trips to colorado in winter with far below freezing temps expecting to have problems... ... . and no problems at all. i don't know how cold it needs to get before grid heaters are nessessary but you may want to see how your truck does without them.



maybe some others will chime in here at least about possible damage from not using grids in cold weather.



good luck, jeff

 

[FourBarR]

its normal,my 98. 5 has done it since new now has 434,971kms. never had a problem relatedto grid heaters. always plug mine in when temperatures go below 40f.

 

[WestTN]

Going down to 9 volts isn't normal. check your batteries. And make sure all cable connections are clean and tight. The cycling is normal. And most likely required in California. It was designed to limit excessive hydrocarbon emissions.

 

[NoSeeUm]

My grid heaters will pull the voltage down close to 12 volts. The voltage will generally be about 14 volts with the truck running.



Jim

 

[PC12Driver]

The grid heaters will cycle for 3 minutes after startup, or until you reach 18mph, whichever comes first. So that part is normal. But I agree, 9v seems a bit low.

 

[DonS]

The grid heaters will cycle for 3 minutes after startup, or until you reach 18mph, whichever comes first.

According to the FAQ on this site, as well as my own experiences in my 2001, time has nothing to do with it. Once the engine is running, the grid heater cycles according to temperature.

 

[NoSeeUm]

We’re going to make an assumption that the lights dim/flutter shortly after start up of the truck. Or, you can get the flutter at a stop light when it is really cold outside (hence cold air into the engine). Having made those assumptions, the problem can be described as “normal. ” Do not spend efforts at the dealership to correct a “normal” truck characteristic. Thanks to writer, John Holmes, for the explanation (Issue 20, page 25). The following is the reasoning:

The Cummins uses a grid type intake air heater. Think of the intake manifold air heater as a powerful hair dryer grid. By design, the Diesel engine is a “heat” engine. For cold weather operation, the Cummins uses the grid heaters to warm the initial charge of air tot he cylinders. Never use starting fluid/ether to “help” your Cummins start. Use of such is asking for an explosion in your intake manifold. Ether has a flash point of 360o.



There are two cycles: the pre-heat and the post-heat cycles. When you turn the ignition switch on, and the temperature is 59o or below, the toasters come on for 10 seconds (down to 15o). If it is between 0o and 15o the “wait to start” light will stay on 15 seconds. If it is below zero, thereby freezing portions of a brass monkey, you will have to sit there for a full 30 seconds while the intake manifold rubs its hands and stomps its feet.

After the engine has been started, the post-heat cycle takes over. If the temperature is below 59o, the heaters are cycled on and off depending on air temperature and how quickly the Cummins gets toasty. You will notice the voltmeter acting like a windshield wiper as the heaters are cycled. Like man, they draw 120 amps! Thus, the light flutter as the battery is working to supply current to all circuits. This condition is normal. It occurs on all trucks manufactured from ’94 to current.

Thanks DonS, I am assuming this is the FAQ you were referring too. I have been trying to figure out exactly what motivates the grid heaters to operate. Thanks again for the link.



I do know that the grid heaters post heating cycle cuts out at around 20 mph. I was not aware of the 3 minute timer, it makes sense, but I will need to test that.



The pre start cycling is pretty evident because if you have the block heater plugged in you get no "Wait to Start". I have a ScanGauge that shows IAT. With the truck plugged in, the IAT is around 80-100F at start. I think that pre start cycling is controled by IAT.



What confused me the most was what temperature actually controls the grid heaters post start heat cycling. Even if the OAT is in the low 20's F the IAT will hold about 80F or so with the grid heaters cycling. So I am not sure, but I am trying to convince myself that OAT not IAT is what turns on the post start cycling.



Jim

 

[jtisdale]

NoSeeUM, where did you get this "scangauge", and how is it hooked up? Does it display actual IAT temp in F?

Thanks, Jim

 

[NoSeeUm]

NoSeeUM, where did you get this "scangauge", and how is it hooked up? Does it display actual IAT temp in F?

Thanks, Jim

ScanGauge



A little spendy, but seems to work pretty good. I bought it to research an intercooler upgrade, so I could see what IAT's were.



Jim