I have a '02 SLT Laramie Ram 3500 dually with 5.9L 24V tubo engine and an odd voltage reading problem. When I start the engine the volt meter rises slowly to a little over 14 volts & then slowly falls back down to 11 - 12 volts before rising again to 14 volts. If I have the headlights on, they dim as the volts fall & brighten up as the volt reading rises. It does this several times and usually stabilizes when the  engine reaches operating temps. Is this something I should be concerned about or is this normal? What could cause this?

Welcome to the forum capn!

That sounds like your grid heaters cycling.  Take a few minutes and do some searches on grid heaters and what they do.  This will help you understand them.  You will probably notice a "click" just before the voltage drop. (that is from the grid heater relays.)  It is pretty normal. 

HTH

Hag

Right on the mark. You find the ECM will cycle the grid heater till a set time or till your speed exceeds 20 MPH.

Thanks Haggar & Mopar1973Man for the info. So it's normal & nothing to worry about. Didn"t want to have to buy an alternator. Appreciate the responses!

Checked Google about the grid heaters & what they do. Does this mean my Dodge diesel does not have glow plugs?

That's correct no glow plugs just a grid heater on the air intake. 

I, myself, would say to double check your battery connections and be sure they are clean and making good contact. This will ensure there is no unnecessary resistance to the electrical system.

As said before, it is common to have the voltage drop due to grid heaters cycling. Seeing the voltage dropping is no issue so long as you ensure good contact at the battery. I had to clean mine again the other day because the dimming of my headlights.

Essentially the electrical draws as much as possible from the alternator while the truck is running, sometimes it needs a little more and the battery supplies it. My voltage was dropping as low as 10V-11V with dirty battery clamps. Cleaned the clamps well and it hasn't dropped below 12 since. Lights are brighter too.

 

Edited January 8, 20169 yr by eddielee

I appreciate all the good advice! My battery cables probably are due a good cleaning & I'll do that tomorrow. I'm a newbie about diesel Dodges but I love the truck, still trying to find out about the go fast/pulling goodies it's supposed to have. The guy I bought it from said it had 150HP injectors, 100gph fuel pump with 1/2" fuel line, turbo back 4" straight exhaust, after market air filter, posi traction front & rear, & a built auto trans with kelvar clutches, billet converter, etc., & an Edge programmer. It's a jacked quad cab dually with big ole tires. I've got a lot to learn yet.

Thanks again

Secret... Lightly coat all lead terminal surface with engine oil not grease. 13 years later still like new...

What I typically see roll in my shop...

5 minutes ago, Mopar1973Man said:

Secret... Lightly coat all lead terminal surface with engine oil not grease. 13 years later still like new...

What I typically see roll in my shop...

I think that has more to do with the fact you wash your engine bay, and clean off any contaminants creating a path on your batteries/terminals.

Gotta love that battery hold down!!

1 minute ago, CSM said:

I think that has more to do with the fact you wash your engine bay, and clean off any contaminants creating a path on your batteries/terminals.

Still after washing I re-coat the terminal with engine oil again. There is only two material that I know of that sulphric acid will not eat. Glass and plastic. Plastic is made from what? Petroleum. Grease works but you'll end up with the grease on your shirt or arm while working on your truck. Engine oil will fade away leaving a thin film that prevents acid from oxidizing the terminals. Take notice to the picture above the positive terminal is black and got corrosion blooms on the copper and steel. This is a sign of acid contact and oxidizing the metals. Like lead oxide is that black coating. It's resistive to current flow typically you know by touch the terminals they could be warm to hot to the touch.

Great info. Thanks