Alernator / Battery / Voltmeter Issues

[WM-300]

Four days ago my 2003 Ram welcomed me with dead batteries. I took it to Dodge for warrantee service. The Service manager said the alternator had a large burned spot on the rear of the case. The alternator was replaced with a new one.



However, now on starting the Voltmeter reads the battery voltage 12. 6 volts and does not come right up in voltage to the alternator output of 14. 2 volts. These reading were verified with a Fluke Digital Voltmeter. If the engine idles for about 2 minutes the voltmeter will then come up and show the higher voltage of the alternator running. If I launch immediately on engine start, by the time I wind thru 5th gear, the volt meter is showing the alternator output. Once the alternator higher voltage output is shown on the voltmeter, it stays at 14. 2 volts until I shut down. On an immediate re-start, the above all repeats.



All my other trucks show alternator output a soon as the alternator spins up. However, I cant remember on my 2003 Ram if there was a lag in the voltmeter showing the alternator higher voltage output. I believe one or two of the batteries got toasted when the alternator overheated. Since this is a warrantee issue, I want to get it fixed quickly as my warrantee expires in 5K miles.



My question; On your 2003 Ram's, how fast does the voltmeter show the higher voltage produced by the alternator running. Must be old age, I cant remember how the voltmeter displayed before the problem.



Thanks

WM300

 

[Turbo1Ton]

I seem to recall that during the colder months when the grid heater cycles, the voltmeter will read battery voltage until the grid heaters quit cycling.



If you start driving before the grid heaters stop cycling, then they shut off at about 18mph or so (I think). This would explain why when you start driving that by the time you are in 5th gear, the voltmeter reads higher.



Hopefully I am not making this stuff up. Can someone else confirm this.



Jeff

 

[Prairie Dog]

Your v meter is somewhat fake. It will not show the voltage swing when you first start it up while the grid heater is cycling (notice the lights still dim & brighten). Seems too many guys were calling the dealer because they didnt understand the grid heater operation. So, in a third gen, it only shows the true voltage after something like 15 or 25 mph is achieved. Your meter is working normally.



Scotty

 

[betterthanstock]

There was some arguing on these threads about whether or not the engine will charge right away, or wait until the grid heaters stop operating. You have proven that the alternator stays off until the grid heater is done cycling.

It's normal, and alternator field goes thru the Cummins ECM, so it knows when grid heaters are done.

It's this way to supposedly protect the alternator from excessive amps. That means that idling for a few minutes, especially with the lights and defrost (AC)/seat warmers/mirror heaters on will put quite a drain on the batteries. A short trip will not make up for the loss of charge, and the batteries will become more and more discharged, until dead.

You can watch the paleness of the map lights at starting, then watch them dim even more as the grid heater cycles on, and then finally reach full brightness when you hit 18 mph (after power doors lock up).

Bottom line, unless you are going on a long trip, don't warm it up by standing still. Start driving slowly, and it warms up faster, and charges up right away.

 

[WM-300]

Thanks Guys, I guess all is well



WM300

 

[JRG]

Bottom line, unless you are going on a long trip, don't warm it up by standing still. Start driving slowly, and it warms up faster, and charges up right away.

Or plug it in

 

[rbattelle]

As long as we're on the topic, I think Cummins made a small mistake in the grid heater programming. Based on observation, it appears to me that the preheat cycle is dictated by the coolant temperature: cold coolant=preheat, hot coolant=no preheat. When I plug the truck in overnight I get no preheat cycle (unless it's super cold out), but I do get a postheat cycle.



I think the postheat cycle, then, is dictated by the reading at the IAT sensor only. That means it'll run a postheat cycle on startup independent of the coolant temperature. This happened just yesterday: drove 1 hour on the highway with an outside temperature of about 25F. Stopped at a store for about 5 minutes, get back in and start it up - no preheat, but I get a full 2-minute postheat. There is no reason for any grid heater cycle once the engine is at operating temperature, as far as I'm concerned.



If I leave the truck parked all day at below 50F or so and it's sunny out all day I get a preheat cycle (cold coolant) and no postheat cycle (underhood air warmed by the sun). If I then drive a short way (exchange warm underhood air with cold outside air), stop, and restart - I get a postheat cycle.



I'm considering installing a manual cutout. I think a better way to have programmed it would be to mitigate the postheat cycle with coolant temperature AND IAT reading.



Ryan

 

[betterthanstock]

: drove 1 hour on the highway with an outside temperature of about 25F. Stopped at a store for about 5 minutes, get back in and start it up - no preheat, but I get a full 2-minute postheat.

Ryan

I noticed that too, like at the post office, I have to drive slowly, then get stuck at a stoplight for a minute or 2, and I hear it cycling on/off.

On my 03 I removed one of the two heaters. No codes, and less drain on batteries. (You probably need them both in Alaska)

The trick is, to get to at least 18 mph (until you lock the doors automatically) before you have to wait at a stoplight.