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Voltage Drop / Lights Dimming on Cold Start

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Old 12-27-2004, 09:09 PM
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Voltage Drop / Lights Dimming on Cold Start

If this describes what you're experiencing when lighting off the Cummins on these frosty mornings,.......
Don't worry, it's normal.

The Cummins uses a pair of 12 volt grid heaters in the intake tract
(imagine two large toaster elements glowing bright red)
that preheat incoming air for easier combustion.
The Ford & Chevy use glow plugs inside the combustion chamber.
As the relay cycles the grids on & off, the large amp draw causes the volt meter reading to drop, and the lights to dim when the relay turns on the juice.
The relay timer will turn off the heaters when the intake temps hit a preset limit, or when the vehicle exceeds a preset MPH (usually between 15-25 mph). edit


Don't panic
.........just another of the experiences you can chalk up to being a member of the Cummins Club.
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Old 12-27-2004, 09:23 PM
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I discovered mine right after I changed the brushes in my alternator. Cranked it up and said "Allright, its working, dang, now it aint, now it is, now it aint, now it is!!
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Old 12-28-2004, 03:07 PM
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I found this out 1 cold morning while on an elk hunt and only have the single battery. Boy I thought I had some major short!
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Old 12-28-2004, 04:25 PM
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Forgot to mention the speed and temp shutoff points vary by year of truck. A lot of people see this routine and panic, lots of wasted troubleshooting hours!
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Old 12-28-2004, 11:03 PM
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Great idea, Shovelhead. It's things like this that make folks like you administrators.

Or gullibility!! Seriously tho' , great idea. Rick
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Old 12-30-2004, 01:06 PM
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Great piece of info that will save some poor soul hours of head scratching! As info, my '01 turns the cycle off at 18mph.
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Old 12-31-2004, 06:06 PM
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Originally posted by ta3834bbl
Great piece of info that will save some poor soul hours of head scratching! As info, my '01 turns the cycle off at 18mph.
Those poor souls could learn alot just opening their owners manual or purchasing a factory repair manual.
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Old 12-31-2004, 07:07 PM
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Originally posted by slowerthanu
Those poor souls could learn alot just opening their owners manual or purchasing a factory repair manual.
That's why we're here.

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Old 01-01-2005, 10:02 AM
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Good bit of information Shovelhead. You explained it so everyone could understand . This is the first diesel I have owned. When I first bought it (new) I thought my goodness the voltage reg. has gone haywire
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Old 01-01-2005, 04:22 PM
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bikers

And some say,those long hair bikers just aint worth a ****, I agree with Shovelhead,thats why this site is so cool,saves alot of grief for someone who has a problem or a question.It surely has taught me alot about these Cummins and saved me a ton of cash.Ride With Pride
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Old 01-01-2005, 11:46 PM
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Re: Voltage Drop / Lights Dimming on Cold Start

Originally posted by Shovelhead
If this describes what you're experiencing when lighting off the Cummins on these frosty mornings,.......
Don't worry, it's normal.

The Cummins uses a pair of 12 volt grid heaters in the intake tract
(imagine two large toaster elements glowing bright red)
that preheat in incoming air for easier combustion.
The Ford & Chevy use glow plugs inside the combustion chamber.
As the relay cycles the grids on & off, the large amp draw causes the volt meter reading to drop, and the lights to dim when the relay turns on the juice.
The relay timer will turn off the heaters when the intake temps hit a preset limit, or when the vehicle exceeds a preset MPH (usually between 15-25 mph). edit


Don't panic
.........just another of the experiences you can chalk up to being a member of the Cummins Club.
Just thought I'd mention that I dont think GM or Ford uses glow plugs. You usually see glow plugs in "indirect injection" diesels as where "direct injection" diesels use heater grids. I believe GM and Ford are the direct injection design. Also for those that have noticed their grids cycling everytime they start up in cold temps, even if the engine is at normal operating temperature, can get a device that overides this feature to save the grids from unecessary cycling when the engine is warm.
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Old 01-02-2005, 01:05 PM
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Re: Re: Voltage Drop / Lights Dimming on Cold Start

Originally posted by KATOOM
Just thought I'd mention that I dont think GM or Ford uses glow plugs. You usually see glow plugs in "indirect injection" diesels as where "direct injection" diesels use heater grids. I believe GM and Ford are the direct injection design. Also for those that have noticed their grids cycling everytime they start up in cold temps, even if the engine is at normal operating temperature, can get a device that overides this feature to save the grids from unecessary cycling when the engine is warm.
Not totally sure about the glow plugs ... a buddy of mine had a late-90s Ford, and it still had glow plugs. Did they just recently switch out, within the last couple of years?
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Old 01-02-2005, 03:26 PM
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Just going off my oooold cobwebbed info
A lot of things probably changed in the last 50 years.........
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Old 01-03-2005, 08:45 AM
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Meh, no biggie. I don't normally pay much attention to Ford or Chevy vehicles these days, for personal reasons. Glow plugs, no glow plugs, it's all the same ... the air has to get warmed up in a cold engine somehow!
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Old 01-09-2005, 08:56 PM
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I just sold a 99 Powerstroke a month ago that I put 250K miles on before I bought my Dodge. Yes they do have glow plugs. Just for the record, The Ford is a good truck. Lots of years of faithful service but after a month with my 02 H.O 6spd, there won't be any going back. This Dodge is an awsome machine
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