[jetflyr]

I have noticed my voltage needle bouncing up and down in the 3/4 range as I drive. I could swear I see my headlights dimming and brightening very quickly as I drive, as well as the dome light. The needle for the charge does not move up into the 1/2 or higher area until a minute or so after I start the truck. Does it sound like this thing is going?

 

[MTN FIELD]

Does it do this after you have drivin it for a while or just after you first start it? One way to check your alt is to get a volt meter and go across the battery terminals and with the truck running you should be somewhere around 13 to 14 volts. It sound like it may be your glow plug relay going in and out not for real sure but my truck does this too when I first start it up.I am sure someone else can give you better advice. hope this helps

 

[bob807968]

yes, mine does this too, specially when it starts up and its cold, but i would check the voltage at the battery terminals just incase. the one on the dash is not that great!

 

[MilitiaAir]

Mine started doing this recently when its cold. But goes away after the glowplug cycle quits. Might be the voltage regulator showing some age. I have a 95 im pretty sure its internal (built into the alt) but if im wrong and there is an external reg just swap it out.

 

[jetflyr]

Does it do this after you have drivin it for a while or just after you first start it? One way to check your alt is to get a volt meter and go across the battery terminals and with the truck running you should be somewhere around 13 to 14 volts. It sound like it may be your glow plug relay going in and out not for real sure but my truck does this too when I first start it up.I am sure someone else can give you better advice. hope this helps

When you say to go across the battery terminials, are you saying to touch + on one side and - on the other? Does this pretty much close the circuit and indicate what you have? The needle hangs low when the truck first starts. I usually make sure nothing is on like the A/C, blower what not. After a couple of minutes it pops up half way or so. I have also noticed that if I let off the gas and idle and cruise in the neighborhood, the lights will dim until I press the accelerator again. It has been years since I have done anything electrical. So, sorry if I look like a dumb A$$.

 

[jetflyr]

The voltage regulator rings a bell. I think I may have changed one out on a Grand Am a few years back. If not built in, is it commonly attached to the back of the alternator?

 

[97psdcc]

The volt meter will read low, apprx. 10 volts right after you start the truck, due to the glow plugs. As far as the lights dimming and getting brighter when you drive, I would check the plug on top of the alt with the single wire and make sure that wire is not damaged and is pluged in good. On the 97 the voltage reg is in the alt.

 

[bob807968]

there is another thread i found that someone had the same question. my needle on my voltage bounces around only in the winter, lights dim, and so on. during the summer, its fine. found out that when you put a reman alternator, at idle doesn't put out the same as a stock alternator, one person put a new pully on the reman to make it spin more and that seemed to work. i am just going to leave mine.

 

[bob807968]

here is the thread....

 

[MTN FIELD]

Hey man dont worry about,we all have questions from time to time. Yes you put the meter on dc volts and put the pos to the pos and the neg to the neg,at start up you will read a little low but after awhile you should be back up to the 13 to 14 volt range.After reading your post have you checked you belt? You could have a loose belt or tensioner pully. I had to replace mine the other day because the bearing locked up on the pulley and it melted the plastic pully.

 

[94_turbo]

the lights dimming--when you first start--is the gp controller kicking in and out--should quit within a minute--then check the voltage at the batt---at 1000 rpm--should hold a steady 13.2-14.8 volts---if not--something in the alt is funky---you can replace the reg in the alt---without removing the alt from truck--4 small torx screws on back--includes brushes normally also--but if it has high miles--and the communtator is cut down much---might as well get a GOOD rebuild--

 

[jetflyr]

Hey man dont worry about,we all have questions from time to time. Yes you put the meter on dc volts and put the pos to the pos and the neg to the neg,at start up you will read a little low but after awhile you should be back up to the 13 to 14 volt range.After reading your post have you checked you belt? You could have a loose belt or tensioner pully. I had to replace mine the other day because the bearing locked up on the pulley and it melted the plastic pully.

Belt appears to be fine. How would you know if it was too tight or slack? I suppose if it is burning up the belt or a pulley it is probably too tight. I need to check the voltage, and go from there.