strange volt meter needle antics...

[Forrest Nearing]

got in the truck and fired it up for the first time today, and drove about half a block and out of the corner of my eye noticed the volt meter needle moving...



I kept a close eye on it, and was watching it jump from the 3rd hash mark (where it normally resides) down to the 2nd hash mark and then back up... frequency seemed to be about every 10-15 seconds and after about a mile it stopped doing it and just went right back to staying at the 3rd hash mark... and didn't do it again...



my gut tells me to test the voltage regulator after leaving it in the freezer for a few hours...



do these trucks have an internal or external regulator?



any ideas?



I drive 4k miles every other month or so, and I need a reliable vehicle... I keep a spare alt, voltage regulator, and battery in my other car...



thanks for any ideas/input!



Forrest

 

[Deerhound]

Heh Heh,

Must have been cool out this morning. The voltage fluctuations you saw is just the grid heater cycling until the temps come up on the engine. Does this all the time on my early 91 W350 when the temperature falls below 40 degrees.



Dale McCan, who has been lurking for a couple of months

 

[Paychk]

Forrest



Rest easy on the voltage fluctuations, Deerhound hit it right on the nail head. The grid heaters (equal to glow plugs) suck juice like you wouldn't believe.



Alan

 

[Forrest Nearing]

sigh...



THANKS!!!



man, I love this place!!!



Forrest

 

[BushWakr - RIP]

Yup, I'll make it a 'full pull' on that conclusion. Mine is the same. Wait till you get a REALLY cold morning. That thing'l go right nuts on ya. One thing I did notice a while back was the degree of swing had gotten to be quite alot. It turned out that a short time later my battery packed up and was not up to the job. Since replacing it the fluctuation was back to "normal" for cold weather starts.



Regards, Bob

 

[Dale Reed]

It really is a voltmeter but my Diesel shop manual says it is an ammeter. Can any of you tell me what page the wiring for the meter is on? Certainly page 8-9 of Diagnosing Electrical Malfunctions is incorrect.



By the "third hash mark" are you including the first mark on the far left? Thanks for the info.