Engine/Transmission (1994 - 1998) Generator Light

[MBNicholson]

I have a 1996 Ram 3500 5. 9 and pull a Carriage Cameo 5th wheel with it. The truck has 136,000 miles. Two years ago exactly in Tucson, I had the generator light come on and not go off. A local shop replaced the generator with a rebuilt. Never had any indication of a problem until a couple of weeks ago when I noticed the generator light on. We stopped to run an errand, and when starting it back up, there was no generator light. About a week later, I started the truck and the light came on again. I shut it off and restarted and no light. It's been a week now with no light. The voltmeter is indicating a proper charge (I never thought to look at it when the gen light was on), but I was wondering if there is something here I should have checked out? Any advise will be appreciated.

 

[Skydiver]

Mine did this same thing. Next time it does it watch your volt meter. My grid heater relays "stuck" closed and was causing the computer to set a fault. It all corrected itself plus the fact that I removed one small wire from each grid relay. I only plug in the grid relays when the temp is below freezing (sometimes). Get ready for a smoke show.

I know I need to buy some new relays, but the grids really tax the alternator. Still running my stock alt.

MBHicholson, may I ask if you have filled out your truck signature located under user control panel?

 

[kenny61]

Last time my alternator went the gen light was coming and going numerous times per day with your week long intermission you need to be checking it with a volt meter to make sure ec=verything is working properly

 

[WilsonF]

Same thing with my 96, light on, good voltage, then fix its self. Off and on for about a year. Then the whole thing went T. U. it was the alt. had it rebuilt at a shop The slip ring was going, but what I think was the problem was the diode pack was bad. That was about two years ago. No problem since then.

Floyd

 

[Skydiver]

How many amps do the grids use? To me it's the closest thing to placing a dead short on the charging system.

 

[MBNicholson]

Both times my volt meter seemed to be indicating a normal charge. I'm embarrassed to say I really don't understand what you are talking about regarding the grid heater relays. I have never been any where with any real freezing weather. We are in Casa Grande, AZ now. Further, I'm really lost when I have to answer whether I've filled out my truck signature under the user control panel. I guess for now, I'm going to go through every connection I have for any corrosion and make sure they are tight.

 

[fest3er]

How many amps do the grids use? To me it's the closest thing to placing a dead short on the charging system.

Each grid takes about 100A. The stock alternator puts out about 136A.



If you had a heavy-enough piece of cable or metal and a solid-enough contact with the battery, you could easily pull 2000A from the system for a short period of time. (At Motorola, we had a battery backup system that would provide 3200A at -27VDC for 20 minutes; it had enough rectifiers to power the load and charge the batteries. In reality, the batteries could easily supply 32,000A or more long enough to get stuff *really* hot: think welding with 750 MCM cable. )



Remember, the alternator and the batteries can all contribute to the current draw. The alternator usually provides most supply because it's running at 14. 8V, higher than the batteries can provide. But when the heaters are on, the alternator sags down under battery voltage and the batteries supply the excess current required.



After 12 years of the grid heaters working, I still have the original alternator. I replaced the OEM batteries 5-7 years ago with Optimas and they're still good. I replaced the heater relays with off-the-shelf Stancor relays about 8 years ago; they're still working as well as they did when new; I'd replaced the OEM relays twice in the first 3 years before I cried, "Enough!"



If your relays stick on, it means they have failed and should be replaced. For about 20% of the cost of a new OEM unit, you can install Stancor relays that, smack skull, will never wear out.