Being this is my first diesel I was wondering if anybody could shed some light on whether my problem is serious. In the cold weather (Canada) I noticed that tonight while driving home my truck began to stumble while traveling at around 30 mph. I opened it up for a couple of miles and seemed to run fine again. However, when I pulled into the driveway and let it idle, I noticed that the interior lights would dim and the voltage would drop from 14V to around 10V. The lights would only dim for a few seconds before voltage returned to 14V again. I'm just wondering if the grid heater could be causing this, or is there some other draw on the system. I believe the rpm's drop when the lights dim, but only barely. The CEL did not come on.

I do believe it may have done this in the past at idle, but did not realize the lights dimming until today.

Thanks


07.5 Mega stock

 

when idling- the grid heater cycles on and off-pulling significant voltage. No need to worry-we all do it.

the grid heater doesn't cycle when running down the road at speed-

check to see if your batteries are any good-cause it will help a little bit-but not all that much. My lights/wipers/windows all slow down a lot when the heater cycles.

 

Thanks very much. I was just thinking earlier today that I haven't had a CEL lately.

 

I have the same problem, whenever I start the engine the voltmeter's needle is going down for a couple of seconds then comes back up for another few seconds and then back down to about 10V and it does this for the first couple of minutes and only when I start the motor. I've never noticed this while driving. It's been happening for a couple of years now but it happened more often in the last 6 months and every time in the last 2 months. Recently I've replaced the Mopar factory batterys with brand new Duralast Gold CCA 850 from Autozone because I had problems starting the engine lately, until one day last week when it just clicked the solenoid. Even with new batterys, I still have the same drop in the voltage.

 

Nothing to worry about, the puter is driving that gauge, not real voltage. It drops when the puter tells the grid heaters to come on, which it tells them to do when it is cold out, and will tell it on/off for a few min. It doesn't seem to matter if the grid heaters are actually hooked up or not as I unhooked mine for a couple years and it continued to dip up/down on a cold start. I'm right about at 208,000 miles.
Back to evening brew. . .

 

the voltage drop should only accure at idel when you first start the trunck and only lasts for a couple of minutes or until you hit 20 mph then the grid heaters shut off it shound not happen anyother time while the truck is running and up to temp this is according to a cummins factory tech not from a dealer he said you might want to check your belt for wear and that it might be slipping and or the alt is getting ready to crap out

 

When I first realized this grid heater/voltage drop issue, I had started the truck and did not notice this happening at first. I drove for 5 to 8 minutes to drop off the kids. When I restarted the truck after sitting for 5 minutes, it was doing this even though I though the truck was "warm" at idle. The outside air was still very cold... Anyway, I stopped driving my truck like this and making short trips because I started getting the emmisions CEL. Then came the deletes.

 

yes even tho the truck is up to temp the grid heater will come on again when you start the truck it is because the sensor in the air intake is see cold air in fact anytime the air temp is below 50 degrees the grid heater will come on at start up and it will operate for at least 90 seconds or until you hit 20 mph then it shuts off.

 

I agree that I may have more of an issue. In the subsequent days I noticed that on two occasions when I started the truck in the morning, the time on the radio, and the presets, had been been reset to their default settings. I will check the voltage output on the alternator the next time it surges, but I'm currently 2 1/2 hrs from home visiting family. So right now, I'm expecting Murphy's Law to make an appearance.

Thanks for the responses.

 

I have seen one truck that kept cycling the heater grids. Please check on the drivers side where the intake horn goes to the engine. There will be a large gauge black wire attached there. Check and see if its cracked on the insulation and/or if there is any yellowing of the intake horn or in the grid heater area. Whatever you do...take caution about what you touch there as it could be scorching hot. The truck I saw this on burned off the wire and the intake horn was scorched back at least 5 inches. The end result was a new heater grid...complete and intake horn. The grid was defective and kept cycling. I think he may have got a temp sensor replaced to but cannot confirm.

 

when my radio and time started to reset to default it was a bad battery that was causing it after the dealer replaced the battery very thing was ok again

 

I just noticed my 08' doing this voltage drop thing like everyone is describing about a week ago. May have been doing it all along and just never noticed it. Outside air temps around 45 - 50 degrees. Didnt matter if I turned the truck off for 5 minutes or half an hour, it still does it. Everything else seems to work just fine. Simply, is this a problem that needs to be looked at or is it normal? Thanks.

 

nope it is normal when the air temp is at 50 or below the grid heaters come on and cycle for at least 90 seconds or until you hit 20mph then they shut off