no preheat, but WIERD post heat!

[jaynes]

so it was about 40 degrees a morning or two ago, thought for sure it was gonna preheat, but it didn't. Instead, it post heated, but not like it ever has before. For this one, the grid heaters came on after i started my truck (could tell cause the dim lights and voltage drop) but they stayed on for about a minute straight, then kicked off. Then they did it again, but it seemed for even longer this time, then kicked off again. Only did it twice, and that was it. Any takers? Relay problem, bad connection... bad pcm, or whatever it is?



jaynes

 

[BushWakr - RIP]

Since I'm industrial grade stupid when it comes to electrical things take this with a case of salt... .



I'd pull off all my connectors and give 'em a good going over... make sure the plugs on the relays on the fender skirt at clean and tight, then pull the sensor from the intake manifold and clean it up if it looks a tad contaminated or dirty...



That's about all I can come up with on this on jaynes...



Ok were's formula or cerberusiam or partsman...come one guys this is your area here...





pb... .

 

[bgilbert]

I think it might have been your grid heaters saying you owe Bill money for that intake hose he sent you months ago ... .

 

[RBergman]

i dont know if it is an issue

my 93 has done that from day one

i never thought much about it.

 

[Msilbernagel]

I had an 89, and I believe it did that...



What's going on is that once air starts flowing, on cold days, it has a cooling effect until the engine gets going. So, you'll find the heater cycling until the temp remains high enough to avoid the 'white cloud' we often see with cold diesels.



As for why not 'before'... ? Keep an eye on it, it may just be that things were borderline before. First frost you get, see if it doesn't do the 'pre' cycle.



Mark

-

so it was about 40 degrees a morning or two ago, thought for sure it was gonna preheat, but it didn't. Instead, it post heated, but not like it ever has before. For this one, the grid heaters came on after i started my truck (could tell cause the dim lights and voltage drop) but they stayed on for about a minute straight, then kicked off. Then they did it again, but it seemed for even longer this time, then kicked off again. Only did it twice, and that was it. Any takers? Relay problem, bad connection... bad pcm, or whatever it is?



jaynes

 

[jaynes]

!!!

AHHH Bill I completely forgot about that!!!



Send me your address and I'll mail a check out to you immediately!! How much was it??



I can be really forgetful sometimes... .

 

[DieselTweaker]

from the sounds of it it's just cycling to keep the intake air temp up.

 

[JLEONARD]

This thread brings up a project that I will be working on in the next week or so.

I need my grids to start when the temps are under 10 deg F or so, but I hate having them cycle for several minutes after I'm up and running... . wipers barely move, heater moter rpm drops off, you guys all know the scene.

I tried disconnecting them last winter, and on a zero deg day getting out of work I was able to fire the truck up, but she didn't like to say the least.

SO... as Greenleaf says I have too much time onmy hands... but I've come up with an idea to solve this ... . I think.

Got the idea from a 2nd genner at our SEEfood challenge a few weeks ago. He uses a oil pressure switch to turn on his "daytime running lights".

So I'm thinking that since the system needs to be closed to stop the grids, I'll use a pressure switch to turn off the heaters once the engine has enough pressure to close the switch rather than wait for the temp switch to send a signal.

Will it work? I'll advise in a couple of weeks after the switch comes in and I get it wired.

Jay

 

[jaynes]

thats what it's doing, Partsman, but duration of time that the grids stay on for the post-heat is way to long. It's never acted like this before, almost kinda like if the thermastor read that the temp was minus 15 degrees and it was doing a preheat for 30 seconds. But they just stick on and keep going and going like a really long preheat. But it really bogs all the electronics down and the head lights get really dim cause the load is so high, like both grids are burning at once . It's really weird. I'm just worried about something getting burnt out or burnt up.



But hey JLeonard I like that idea of the oil pressure switch. I agree; once my engine is running, then its running and I don't really care about post heat... my foot takes care of that issue . Keep us posted on that!! Also does anyone know of a thread that talked about a manual preheat switch but still let the computer take control as well? I tried a search but couldn't come up with anything... I really liked that idea, cause if anyone knows, my truck always sucks at preheating when it's cold and it starts rough. I think I could take better control of that myself and have easier starts in the winter. Thanks a million!!



jaynes