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Discussion Starter #1
I had a weird little "electrical anomoly" this morning! Truck was parked outside, block heater on the timer and temps were about 8 degrees F. I got in, turned the key and got the "wait to start" light for about 4 seconds (typical for the engine on the block heater). Cranked her up and volts were at 12 for about 5 seconds (glow plugs and intake heater) then came up to just under 14 for about 5 more seconds (just intake heater) and then up to 15 and headlights brightened up and ready to rock. This is the standard cycle that has been repeated regularly for over 4 years now - even when "cold cranking" in the evenings without block heat at very low temps.

Now things get strange. I diddled around getting the defroster turned on, seat heater, changing the radio and getting my work pass out of the console and when I looked up, I was at 12 volts!:confused: I noticed that the headlights were really dim, too. Just as I was wondering if my alternator had died, it jumped up to 15 volts and the headlights brightened back up! Well, I backed her out of the driveway and headed off. I go half a block, turn right, go two blocks and then turn left to head into town and on to work. At the left towards town, I glance down and I'm at 12 volts again!:( I watch the voltmeter as I head up the street and within a block, it jumps back up to 15 volts. Stays at 15 volts the rest of the 40 miles and 35 minute drive out to the worksite.

I know there can be extra glow cycles, but this is entirely new. I wonder if the alternator is getting "tired" after 4 years and 118,000 miles, or the glow plugs, or some combination of the two?:eek::
 

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Tom,

I had the same problem on the suburban a few years ago. Replaced the altenator, but no help. Turned out one of the batteries was bad. Something loose inside the battery. It would read 14 volts, then shake it good, and it would read 10 volts.

I'd check batteries first, before the alt.

Good luck.

Steve
 

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Thanks for the info, Steve, but I hope it's not the batteries - I have two Optima red tops that are less than a year old. I will take a look at my cables and connections when I get a chance. (I work 4 tens, leave at 0530 and don't get home 'til 1800, so it's dark as pitch going out and getting home.) I will have daylight and all day Friday to check things out if it continues. It was just a strange change from normal operations after 4 years and 118,00 miles!
 

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Mine was doing similar things when one of my batteries had an internal short. However those were the Delco's, I hope the Optimas don't do the same!
 

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When I installed optimas some yrs back, I found that the cable connector bolt/stud was too long ~ yes, felt tight w/wrench but the connector wasn't making firm contact. Its possible for oxide (white stuff) to build up between the cable/battery connector surfaces also.
 

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Still acting up? Don't forget to let us know what you find out tomorrow. I'm curious to hear what it is.
 

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Discussion Starter #7
Thanks for the inquiry, sled mack. I watched it like a hawk last night and again this morning and everything was normal. I will be popping the hood and checking all my cables and connections in the morning - I'll let you know what I find, if anything.
 

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Discussion Starter #8
Well, got under the hood this morning. Both of my positive cables were LOOSE! They weren't "sloppy loose" but you could wiggle both of them by the cable. The negatives were nice and tight. I popped them off one at a time to check for oxidation or arcing. They were okay, but not tight as they should be. I think the heavy red rubber jacket on the cable ends combined with heatup/cooldown in service worked them loose. 10 minutes with a 6" crescent and she's good to go! Glow/intake heat cycle went normally and the gauge is showing about 2 volts more than it was before during all phases of the cycle. I guess I'm gonna have to add checking the battery cable bolts to the oil&filter routine!
 

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Glad to hear it was nothing major. Looks like something I should be adding to my checklist as well.
 

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I Have A 2002 Gmc 2500hd. Ever Since 65000 Miles, Every Single Time I Start This Truck Hot Or Cold My Voltage Sits At 11 Volts For About 15 Seconds And Then It Pops Up To 15. Lights Come Up And So Fouth. I Continually Check Everything In The Truck. Batteries Are Good. Cacle Connections Are Good. Everything Is Fine. It Has Been That Way For Almost Two Years Now. Any Thoughts. 141,000 Miles On The Truck, I Have Only Had To Change Fluids, Filters, Tires, Nothing Else. Got To Love This Truck. Cmg Hydraulics Inc. Dayton Ohio.
 

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I Have A 2002 Gmc 2500hd. Ever Since 65000 Miles, Every Single Time I Start This Truck Hot Or Cold My Voltage Sits At 11 Volts For About 15 Seconds And Then It Pops Up To 15. Lights Come Up And So Fouth. I Continually Check Everything In The Truck. Batteries Are Good. Cacle Connections Are Good. Everything Is Fine. It Has Been That Way For Almost Two Years Now. Any Thoughts. 141,000 Miles On The Truck, I Have Only Had To Change Fluids, Filters, Tires, Nothing Else. Got To Love This Truck. Cmg Hydraulics Inc. Dayton Ohio.
This is normal. When your truck first starts up the glow plugs and intake heater are on and they draw a ton of power. This is why you see low voltage for a bit until they go off.
 

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Discussion Starter #12
Max is exactly right, tonyjames. If you read my first post, I was concerned because that normal cycle was different than it had been for over 4 years. More volts and three consecutive cycles.
 
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