Engine/Transmission (1998.5 - 2002) Grid Heater question ?

[JPLB22]

I hope my question doesn’t sound like I’m just blubbering..... On cold mornings I always plug in my CTD, using a timer to turn it on two hours before I start it. Then after oil pressure comes up I will up the idle ( with my foot ) to about 1250 rpms. And of course my grid heaters are going through there cycle. But when I idle up it seems that the grid heaters stick on the whole time. I think that because when I idle up the lights dim and my EGT’s go to about 375, and they stay that way until I let off the peddle, then after I let off the grid heaters start to cycle again.



Now this morning it was not cold enough to plug in or for the grid heaters to cycle. So I decided to idle up to see if conditions were the same. When I idled to 1250 the lights did not dim and EGT’s would not go above 300 ( on a warmer morning even ).



So my question is... . are my grid heaters staying on when they are already in there cycle and I up the idle to 1250 ??



Could not duplicate results of 375 EGT and lights dimming when the grids were not already in there cycle.



Sorry fo being so long.



Jeff

 

[dresslered]

I actually have LED's mounted on my center console to tell me which grid heater is on and when. What I have never been able to determine is the algorithm that is used to control them. I believe that they use the intake air temperature (IAT) sensor and the coolant temperature sensor. Under most 'cold' circumstances they both come on initially. Once I start driving or let it idle for a while, they then toggle back and forth (alternating) for a bit. As soon as you reach a certain speed (or a certain temperature combination is achieved), they shut off for good. I have seen some mornings where I would expect them to come on and they don't, while on other mornings they come on when I would have never expected them to. They seem to have a mind of their own. I believe you when you say that you can't duplicate their behavior.

 

[JPLB22]

dresslered... . Thanks for the reply. I am interested in your LED’s for indicating when and which grid heater is on. How did you wire them up etc...



Believe it or not, I was driving in town last winter after getting off the freeway, sitting at a stop light, and my grid heaters started to cycle !!?? It only took me a second to realize the rpm change and lights dimming was the grids. But needless to say I was dumbfounded, seeing as my coolant was up to full operating temp.



When I wrote above about not being able to duplicate, I was speaking of the EGT’s and lights dimming. I think the only way for me to get the EGT’s up to 375 while in park is if one of the grids is stuck on when I idle up. Because if they’re not on when I hit 375 then I should have been able to reach 375 this morning when I idled up with out the grids ever starting a cycle ( it was about 50* this morning compared to 38* Wed. morning ). When the grids have started there cycle first, and then I idle up, while I’m holding it at 1250 rpms the lights stay dim and there is no cycle, but I am able to maintain a higher EGT than when I idle to 1250 and the grids never cycled before I idled up.



If I had the LED’s there would be no question ??



Sorry I can’t explain my thoughts in shorter sentences.



TIA



Jeff

 

[Ncostello]

JPLB22... mine operate just as yours do. I really dont think they are even needed 99% of the time. I guess I dont mind the initial heat when I turn the key to the on position... its just that constant on-off-on after its running. I dont need it. Plus even after driving for a long while they will still cycle at stop lights if the "special" conditions are met.



I like the commonly known idea of an oil pressure switch to disable them after the engine is running.

 

[dresslered]

Grid heater LED's

They are just tiny 12V LED's which include dropping resistors for the 12V operation which are wired to the terminals connected to the grid heaters (when the grid heaters are hot, there is 12V present). You can use 'tiny' wire as the LED's use very little current. They should probably be fused unless you are using very, very thin wire (which would then blow in the event of a short). They're fun at Christmas!



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