Engine/Transmission (1994 - 1998) Grid Heater

[Fatboy]

I believe there is a problem with mt grid heater based on the fact that I can be below freezing and start the truck after "wait to Start" goes out, truck starts but no grid heater cycling via ammeter gauge, lights dimming etc. I shut it down, go through the normal pre-start sequence, start it a second time and the grid heater cycles



Any ideas ?

 

[illflem]

The heater only cycles after starting if the temp is below a certain point. As for why it does cycle the second time you start it you've got me.

 

[radixr]

The grid heater is controlled indirectly by the Intake Air Temperature sensor which is located in the intake manifold. If your engine was still a bit warm from recent running, the grid heater probably would not cycle when starting. But the incoming cold air will cool off the IAT and a prompt restart will cause the grid heater to cycle because the PCM thinks the whole engine is cold based on what the IAT is signalling.

 

[Fatboy]

Radixr,

I know what your saying, but the heater fails to cycle on a stone cold engine, (off for days... ). Once started, shut it off and immediatly restart and the grid heater begins its cycle as it should have the first time?

 

[GAmes]

Once it has started, who cares. I fixed mine not to cycle after it has started.

 

[illflem]

If it cycles before you start it don't worry

 

[JohnE]

The grid heaters are controlled by the Dodge <strike>ECM</strike> <b>PCM</b>.

The <strike>ECM</strike> <b>PCM</b> takes input from the Intake Air Temperature (IAT) sensor and vehicle speed sensor (VSS) to trigger one or both grid heaters.

I would check for loose connections at IAT and the grid heaters and controlling relays below the battery tray on the driver's side. You might want to check the icecube relay on the firewall, too.



<em>edit

After checking for loose connections, verify that each power relay (located below the battery) function. If the power relays function then check the ice cube relay on the firewall. If If the relay circuits are all good, then go to the IAT. (Sorry, I don't know how to troubleshoot them. )

If everything checks good, then it may be the <b>P</b>CM.

end edit</em>



<strike>ECM</strike> <b>PCM</b> faults are the toughest to troubleshoot.



Good luck



<small><em>

edit:

I am so used to calling them an ECM (generic term) that I forgot to change hats to dodge terminology.

 

[fest3er]

Originally posted by illflem
John, think we went though this before, no ECM on a 12 valve

And even onthe 24V, the ECM doesn't control the heaters. Perhaps he meant 'PCM'?

Fest3er

 

[JJW_ND]

ECM (PCM) does exist and Control grids

Bill... . I think it might be called a PCM but it does exist on our 12V trucks. In a 5sp, controling the grids is about the only thing it does.



NO PCM no GRIDS.



It is just smoke control once the engine is running. I doudt it helps drivability at all when extremely cold. Changes to pump timing or fuel quality (additives) have much more effect.



I still think if for some reason it decided to get to -40 one night and my truck was setting out with no plug in available, I would disconnect the grids and use either to start. Grids really help get things going, but the also really drain batteries.



jjw

ND

 

[RichV]

The grid heater cycles for three minutes after a cold weather start up. It will stop cycling after three minutes or if you drive more than 30 mph. This is what I have seen, and would suspect that a PCM is controling that.

I have driven my truck for a good part of a day, and would start it up, I would observe heater cycling, even though I did not have the wait to start indicator stay on like a cold start.

If you don't see your volt meter changing, as you know its not working as it should.

 

[JohnE]

I have trouble changing hats on these issues.

WE install the following <b>E</b>CM's on a transit bus:

Engine ECM (comes on the Cummins or Detroit Diesel engine)

Transmission ECM (Allison, Voith or ZF)

ABS/ATC ECM (WABCO)

Chassis ECM (An Allen Bradley PLC)



I'm not to keen on Dodge 24 valve applications as my territory is ISC & ISL. The Cummins ECM controls the gid heaters for us.



I edited my previous post.

Thanks JJW-ND for clarifying

 

[dremelts]

Re: ECM (PCM) does exist and Control grids

Originally posted by JJW-ND

Bill... . I think it might be called a PCM but it does exist on our 12V trucks. In a 5sp, controling the grids is about the only thing it does.

I believe the rear wheel anti-lock brake is tied into the PCM also.