Engine/Transmission (1994 - 1998) Grid heaters keep cycling

[CGomulka]

on my way to work this morning at each stoplight and parking I could hear the grid heaters cycling on and off. It was about 55 degrees out and it takes me about 25 minutes to drive in. I'm guessing that they are not supposed to keep cycling like that. Any advice on what may be wrong or how to diagnose the problem?

 

[Howard Durand]

It is not abnormal for the grids to cycle at 55 degrees ambient. 25 minutes seems to be exceptionally long.

I would suspect the intake air temperature sensor. It is located in the intake manifold behind the AFC housing.

Unplug it and short the wires together and see if that stops the cycling. If so, the sensor is probably bad.

 

[DPellegrin]

There is a sensor on top the motor near the air horn that senses the temperature they are about $40 at cummins and really easy to put in.

 

[Katmandu]

It is not abnormal for the grids to cycle at 55 degrees ambient. 25 minutes seems to be exceptionally long.
I would suspect the intake air temperature sensor. It is located in the intake manifold behind the AFC housing. Unplug it and short the wires together and see if that stops the cycling. If so, the sensor is probably bad.

At what Temperature does the Heater Grid get activated at ??

How long is the Heater Grid "supposed" to cycle ??

Is it dependent on the Temperature of the incoming air or is it on a Timed circuit ???

 

[Howard Durand]

The intake air heater cycle begins at or below 59 degrees F. As far as I can find out in the manual, they will cycle until the intake air exceeds the 59 degrees but, in reality, I believe that they do time out after a few minutes once the engine is running. I haven't found anything in the manual that says that though.

 

[Signal73]

Its supposed to shut off over 15 MPH also, right?

 

[Katmandu]

Its supposed to shut off over 15 MPH also, right?

Someone replied to another thread of mine that the VSS is supposed to turn off the heater grid above 18-22 MPH.

So my question then is this... .

So it's "Normal" for the Heater Grid to cycle whenever the ambient temperature is BELOW 59 F and the vehicle speed is BELOW 18 MPH ??

 

[Signal73]

Not IMHO. Mine stops once I reach the end of the block and dosent come back on no matter how cold it is.

Goes for both my 95 and 06.

 

[Vaughn MacKenzie]

I have never really checked but if my truck is just idling and I haven't driven yet they'll shut off in less than 5 minutes.



Yes once my truck is warmed up the grids do not come on again.



I'll try it myself by letting my truck idle and see how long they stay on, but I got to wait for Fall weather to return (it's been in the 70s today since 6 am!)



Vaughn

 

[EHarvey]

just went on googe and typed in dodge grid heater and it seems this is normal to stay on only for a little while. other guys were saying they put a circut in the line and a toggle swith to shut it off when not needed. . but pretty sure it voids the warranty if your still covered. hope it helps

 

[Howard Durand]

The problem with the service manual is it does not put all the information about any one component of the vehicle or engine in one place where it can be read through and gain total understanding of the subject. Some questions are not answered anywhere.



Regardless of what is said about the Haynes manual, they do provide a complete description of the operation of the intake manifold heaters.

They state that after the engine has started, (Post Heat Cycle). The air temperature in the intake manifold must be below 59 degrees F and engine speed above 475 rpm for heating to continue.

It also states that the PCM will shut off the grids if the engine stalls or if the vehicle speed exceeds 10 mph during Post Heat Cycle.

 

[6BT-Dakota]

My grid heaters have been removed from the truck. Just ask the guys at the Seefood challenge.

 

[Missouri Mule]

In the 96 service manual the post-heat cycle will run the heaters for 3 1/2 minutes unless the engine stalls, the starter is operated more than 10 seconds and if the vehicle speed is more that 10 mph.



Preheat cycle will shut down if starter is operated.



The problem could be the heater relays or the PCM.

 

[Katmandu]

They state that after the engine has started, (Post Heat Cycle). The air temperature in the intake manifold must be below 59 degrees F and engine speed above 475 rpm for heating to continue.

It also states that the PCM will shut off the grids if the engine stalls or if the vehicle speed exceeds 10 mph during Post Heat Cycle.

Will the heater grid begin cycling again when the vehicle speed drops below 10MPH and the ambient temperature is below 59 degrees F ???

 

[Howard Durand]

I believe that once the cycle has terminated it will not begin again until ignition has been turned off and a new start cycle is begun.

 

[Katmandu]

I believe that once the cycle has terminated it will not begin again until ignition has been turned off and a new start cycle is begun.

What's wrong with a system that continues to cycle AFTER 3 1/2 minutes ???