Lights go dim...

[slapshot44]

My truck intermittently experiences a voltage drop when I let off the accelerator. The voltmeter will show a drop of several volts (like when the glow plugs and warming grid are on when cold starting), the lights dim, and the blower motor slows down, just for a second or two, and then everything returns to normal??? Anyone have any ideas?

I seem to remember at least one other thread describing this problem awhile ago, but I can't find anything using search.

[Cowboy_120]

I have the exact same problem. I took it to the dealer and ofcourse they say that they cannot replicate the problem. It seems they say that about everything! I am not sure what causes it, but it doesnt seem to affect anything else.

[Kennedy]

I've seen this too. Seems like a voltage regulation issue. Not too big a deal as it comes right back up, but annoying nonetheless...

[SoCalDMAX]

Mine does it immediately after startup, along with increased alternator whine, it's just the charging system handling the load from the starter, glow plugs, etc.

On the positive side, when I thump the tunes for long periods, no problems. First vehicle I've owned that came with enough charging/storage power from the factory.

Regards, Steve

[TLA]

Next time it happens, check your RPM. It could be that your engine is dropping to idle if the TC is unlocked, and the load is sufficient to cause the drop. Does it happen more towing?

[slapshot44]

Thanks for the replies. The really annoying thing is that its done it a few times in all conditions; both cold and hot zigzagging through residential streets, hot and loaded, hot and unloaded, daytime, nighttime, stereo (400W amp) on, stereo off ... Its not consistent enough to pin down to one set of parameters, except as TLA noted it does seem to only happen when the truck drops to idle right after letting up on the accelrator. But I've never seen any other truck I've owned do this. Of course, they have all been gassers so is this just a diesel thing?

I'm thinking that since the voltage drop seems to be the same as when the glow plugs and grid are on, is there some glitch in the software allowing the glow plugs and grid to be momentarily activated under some unknown conditions? Would a tech II show when these devices are on and if so, would it be possible for someone who has one and whose truck also shows these symptoms to monitor the parameters and catch the truck in the act?

I guess its good that the only things we seem to have to complain about are these minor annoyances... ;)

Thanks again for the help.

Denny

[ZFMax]

Has nothing to do with the TC ... mine does it and I have a 6-speed. Generally see it when running at highway speeds and drop off the throttle in preparation for an upcoming turn. The lights go dim for a second or two.

If I thought there was a snowball's chance in Hades of getting it corrected, I'd make the effort, but judging from how hard it's been to get obvious things fixed, I ain't even going there. Hopefully it's nothing serious.

[Dave_WB3FYV]

This was discussed a while ago, here's a link to the thread I found on the Trucks and Drivetrain forum:

http://forum.62-65-dieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=7&t=001841&p=

There is still no solution that I'm aware of, most dealers can't reproduce it. My truck does it occasionally, doesn't seem to matter warm or cold, day or nite - just when backing off the throttle, and not every time. It seems to do it less frequently when the engine is very warm, like yesterday when the air temp was in the 90's.

It's just something I have learned to live with, but it is annoying since more light is usually needed when slowing down, like for a curve in the road!