I was driving to work this morning and the gen light came on, indicating an alternator problem, I assume. It was just below freezing last night. When I shut the engine off and re-crank it, the light goes out for about 20 seconds, but comes back on. I've got 96k miles on it and I'm thinking it's probably time for a new alternator? I don't have a lot of time to tinker with it. I did a thread search on this earlier and read about a couple of other possibilities, to include new brushes?
The voltmeter is indicating right around 12 volts, a little less after cranking and then charges back up to about 12 +/- .2 or so.
Anyone had this problem on their 12V? And how did you fix it?

Thanks in advance,
WHIFF

 

Ive had that problem

But mine was the worst possible scenario, after replacing the starter, alternator, battery cables, both batteries, it turned out to be my PCM, bad voltage regulation. My problem was though, that i would overcharge the batteries, my needle would rest at 16 volts so to say even at 18 at times. I really hope this isn not your problem. if so many people have had luck adding an external regulator, unfortunately for me i didnt and i had to replace my PCM, brand new and too expensive as of 6/2005.

NOw you might also wanna check your engine control fuse, its a 30 amp fuse under the fuse box under the hood to see if that has failed or not.

Best of luck and i hope u dont have worst case like me...

Type in seach GEN light again by me TxDiesel007 there is some more reading there....

Tx

 

mine came on a couple of years ago but i found the problem to be in the trailer lights connection.

salt is an excellent conductor!

 

Thanks, TxDiesel!
I think your thread might be just what I'm looking for. driving home this afternoon, the dang light didn't come back on at all. It had been coming on all morning and early afternoon. Then again, it was a lot colder at that time. It doesn't sound like the alternator, since it's intermittent. I'm wondering about the PCM now.
Anyone else had an intermittent gen light around winter time in the cold?

 

BUMP TO TOP...

and lets pray that it is not your PCM.. trust me you dont want that to hit you at all, especially around this time.... did you check the engine control fuse? (Pink 30 amp under fuse box under hood)..

Tx

 

Thanks, TxDiesel.
I ran some tests yesterday and it's my alternator. I guess I shouldn't have been surprised, since it's nearly 10 years old now. So I forked out some cake and got a new one. The light is out, and my system charges to about 13.5 volts. Many thanks to TxDiesel007 and Infidel for their help on this issue.

I'm still planning on hooking up an external voltage regulator, though!

 

I have to watch this...

Lately I have found my lights to be flickering slightly. The gauge doesn't move, stays just over the 14V mark, but my lights have a faint flicker.

I am really hoping its not the PCM too...

 

My 04.5 diesel is dimming lights inside ,noticable when started up amp gauge is under 13 or so then drive 1/4 -1/2 mile then will show charging normally no problem .Only when started cold mainly !

 

No worries, thats just the heater grids cycling.

Lil Dog, mine did that before the alt went out, so you can plan on it.

 

Must note that the typical failure for these alts is the brushes. You can get brushes (or an assembled brush plate) from Fosters and rebuild it- after one brush replacement it's bearing time. Now, as the brushes wear they create dust which tends to make the brushes stick in the holders creating poor contact and turning on the GEN light. Rap on the alt housing with a rubber mallet a couple of times see if that cures the light- if so order your brushes! Been there done that. Lasted almost another year before the alt died- but it went at the worst possible time- 8 pm on a fri night in a blizzard while I was plowing!

 

if you have an electric over hydralic plow like i do, it draws quite a bit of amperage.

 

Justme is right... Most of the time when the alt gets flaky in cold weather, it's the worn brushes sticking in their holders from cold oil/dirt/carbon etc.
When you pull the brush rig out and take a look how short the brushes are, you'll say "no wonder!"...


K.

 

WHIFF,
How many miles is on your alternator? Wondering if I should start thinking about replacing my brushes at 179K even though it is charging correctly.