Archived Husband needs help

[MFranz]

Truck voltage gauge is erratic. Truck had already been driven and engine was warm. Started the truck, voltage gauge flucuated with head lights on, lights would dim repeatedly. Is this related to preheat circuit warm up or is this a sign of both regulator and/or alternator going out? Is the voltage regulator built into the alternator? If we have to replace the alternator should we go to a dealer or what would be the recommended after market one to get.

Thanks, Ann

 

[NNovak]

Even if the truck was warm the grid heater still may kick in causing the dim in lights and voltage meter dropping. I see it regularly now that WI is done in the single digit temps. If it is doing it after you drive it for a bit then it is a different issue. Mine stops after I do I get out of my neighborhood iddeling and get on the 35mph road.

I had the same question a few months back.

 

[ScottLewis]

I note you're in SoCal so grids may not be the problem. The IAT measures the intake air temperature and tells the PCM to activate the grids when it's cool enough. On all our newer trucks the regulator is part of the ECM (or PCM). Many of the chain parts places, like Kragen, Schucks, Pep Boys, etc. will test your charging system for free (if you ask nicely) so you can determine where the problem lies. The dealer is a good place to get it done but it will be at the highest price.

The first thing I would do is to make sure all connections to the IAT (at the rear of the engine), alternator, etc. are clean and not loose. Then see if the alt. is charging and go from there.



Dan

 

[MFranz]

Thanks for the response, he will check it out.

Ann

 

[PRout]

On the coolest mornings of the year in so cal my truck does the same thing. As said above its "probably" just the grid heater kicking on. If I remember correctly, the ecm is programmed so that it wont do that at speeds above 20 mph so if it quits doing it after 20 mph, then you can be pretty sure thats what's going on. Mine is normal and yours probably is too. It can really pull the volt meter down and slightly dims the headlights due to a lot of power being drawn when it cycles on.

 

[fox]

Below 60 degrees the grids cycle. Mine do it at any speed for a given time, not sure what that is, but I can get 3 miles or so before it stops.

Check the batteries and cables, they may be getting week.

Is this the first winter for you as a Cummins owner?

 

[bmoeller]

Everything sounds normal to me.

 

[Loren]

Ann,



If it stops after two or three minutes, it's the grid heaters and nothing to worry about.



On cool days, even if the engine is warm it will cycle the heaters for a few minutes after starting to heat the intake air. This will show up as lights going dim to bright to dim, etc. , as well as a dramatic cycling in voltage on the voltmeter.



The key is that if it's just the grid heaters and they are operating properly, it will stop after a few minutes of driving.



Your description sounds like the grid heaters. I don't think you have a problem. Good luck.



Aside: Southern California is not always quite as mild as everyone assumes. When my family went camping in Death Valley we would often wake up to find the water frozen in the water bag. (Who among us remembers water bags?)



Loren

 

[Missouri Mule]

The grid heaters (intake manifold heaters) have a pre and post cycle if after starting the intake temp sensor detects air colder than 60 degrees F it will cycle the heaters for 3 1/2 minutes or speed up to 10mph (as per 96 service manual) .

 

[Giachino]

On the coolest mornings of the year in so cal my truck does the same thing. As said above its "probably" just the grid heater kicking on. If I remember correctly, the ecm is programmed so that it wont do that at speeds above 20 mph so if it quits doing it after 20 mph, then you can be pretty sure thats what's going on. Mine is normal and yours probably is too. It can really pull the volt meter down and slightly dims the headlights due to a lot of power being drawn when it cycles on.

I agree, mine did it in so cal and now az during winter... .

 

[MFranz]

Thanks.

Thanks all for the feedback. Looks like thats what it was. The grid heater. I had noticed it in the past when first starting on cold mornings. I didnt realize that

it could happen after the engine had warmed up.

Thanks again.

Mike

Husband of Ann.

 

[CFAR]

It should do that every time you start, it's just the grid heaters cycling.