Weird Charging Issue
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Fleet Mechanic
Joined: Jan 2011
Posts: 1,793
Likes: 74
From: Richland, WA
Weird Charging Issue
So I've noticed that my truck has been getting harder to start even when it has been plugged in. Then once it starts, the charge gauge reads really low, just above the 8 and all of my lights are dim. Once I start driving the gauge begins to climb and about 30-35 mph it jumps to the 'M' in normal and all the lights brighten to normal. It drives normal the whole trip, then I shut it off to run in the store really quick. When I come back, same thing happens. I figure batteries aren't holding a charge and the lights brighten when the alternator kicks in under a good load.
So last night I dropped in 2 new batteries and this morning the same thing still happened, except for the rough start. It seemed to start normal. Any ideas?
So last night I dropped in 2 new batteries and this morning the same thing still happened, except for the rough start. It seemed to start normal. Any ideas?
Lead Driver
Joined: Oct 2003
Posts: 8,476
Likes: 37
From: Madison, WI
The alternator doesn't "kick in", it's charging the whole time the engine is running. The voltmeter will always read low for the first 1-2 minutes the engine is running. That's because the glow plugs pull the voltage down considerably. The jump you see has nothing to do with the speed, it's when the PCM shuts off the glow plugs. What you're seeing is perfectly normal.
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Fleet Mechanic
Joined: Jan 2011
Posts: 1,793
Likes: 74
From: Richland, WA
I meant to say that it is as if the alternator kicks in, but the alternator will put put more current when the engine is under a load than when it is just idling.
If this is normal, then my truck hasn't been running 'normal' for the last 2 1/2 years I have owned it.
If this is normal, then my truck hasn't been running 'normal' for the last 2 1/2 years I have owned it.
Post Fiend
Joined: Dec 2010
Posts: 10,121
Likes: 3
From: Orrville, Ohio
Have you recently replaced the Glow plugs or the GPR? Mine does the exact same thing, but I think my alt is getting weak. It seems not to be charging as well as it should be. The lights on mine get visibly brighter when the GP's shut off, and when running teh lights and heater blower at the same time, I can hear the blower pick up speed when I turn the lights off. I think mine is a case of the alt getting weak.
Post Fiend
Joined: Dec 2010
Posts: 10,121
Likes: 3
From: Orrville, Ohio
All I will say is that I was really surprised with 8 working Beru GP's how far down there the voltmeter goes when the GPR pulls in. But I have noticed mine acting a little sluggish at other times too. My drive to work is pretty short though and I have the alt off my other engine, so swapping it would be pretty easy.
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Fleet Mechanic
Joined: Jan 2011
Posts: 1,793
Likes: 74
From: Richland, WA
Well, it could be that it has been doing this since I replaced the GPs and I just haven't noticed it until this week. I still think I needed the batteries anyway. I think one was purchased in 06 and the other in 07. So they're pretty old and having 4 bad GPs last winter didn't help any...
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Lead Driver
Joined: Oct 2003
Posts: 8,476
Likes: 37
From: Madison, WI
Yes, the above is based on the assumption of all glow plugs working. Fewer working GPs means less current draw, less voltage loss. So it's just more noticeable now with the new plugs.
And indeed, with batteries of different ages, you're really only as strong as the weaker of the two (voltage-wise), so you effectively had two 5-year-old batteries, working extra hard to overcome the previous GP issue. New battery purchase was well-advised and well-timed.
And indeed, with batteries of different ages, you're really only as strong as the weaker of the two (voltage-wise), so you effectively had two 5-year-old batteries, working extra hard to overcome the previous GP issue. New battery purchase was well-advised and well-timed.
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Fleet Owner
Joined: Aug 2004
Posts: 20,419
Likes: 197
From: AZ
I have two new batteries, a new 220 amp alternator and new glow plugs. On start up the glow plugs, drawing their normal amount of juice, still pulls down the amp gauge. Just the way it is. I really like my GP kill switch, stops that from happening again if the oil temp isn't hot enough on the next start up and the glow plugs want to run again. If in theory, you make a lot of short runs from store to store lots of times, you will end up with dead batteries and/or burned out GP's. I use my GP's on the first start of the day and then shut them off. IMHO 
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