Okay this is weird.

So lately my "Battery/Alt" lamp has been going on and off as I drive but the alt is still putting out 14.5 volts whether the light is on or off and it's usually very stable as this happens too. Only maybe 3 times over the last 4 days have I noticed the voltage spike to 15 -16 volts but this only happens for a split second then flicks back to the regular 14.5 volts and stays there.

(I notice the spike because my inverter has an alarm for over/under voltage. Also, I have voltmeters in my dash for both batteries as you can see in my Build thread)

I checked the leads from my fuse box to the alt and they seem okay. The alt is a little over a year old and it's a DC Power 180 amp unit.

Anyone with any suggestions?

 

The voltage spike could have something to do with it. I would look at the wiring diagram for your truck and see what else is tied in the light on the dash.

 

Since the light goes on in a over voltage situation as well as under That is why your light is coming on.

Sounds like your voltage regulator is on the way out .

I just hope it does not let you sit.

Are you running some sort of battery isolator with your dual batteries??

Depending just how things are wired it would not hurt to look at that as well

 

You can also check the cable for the alternator to the battery, or isolator, whatever you are running. If that is frayed, corroded or some of the strands have broken inside the insulation, you will have this exact same problem.

 

Check alternator brushes.

 

Has this been happening since the alternator change? can you run a stock one to verify it isn't the alternator? Sometimes these big alternators struggle to keep up at low rpm/idle unless they run an underdrive pulley to speed up the alternator.

 

The light still comes on even when the alt is putting out the normal 14.5 volts.

Yup just your generic 4 post isolator which is working fine.

Did the 3 wire upgrade when the new alternator went in and everything is in primo shape.

It just started happening on the weekend.

I've been thinking about getting a back-up one from the wrecker to eliminate the alt being the issue.

Possible but unlikely with the DC Power alternators as it cranks out 120 amps at idle.

 

Well trouble shoot the charge light circuit.

Starting at the plug on the alternator .

Is this a plug and play alternator swap from factory or is some custom wiring needed ??



Is it possible your light is coming on because another circuit is grounding through the charge light??

something within the gauge cluster??

 

Direct plug n play. OEM connector plugs right into it which is one of the reasons why I chose it.

That's kind of where I'm leaning too.

 

Check your ground straps and wires for corroded or loose connections.

 

Well I'm leaning to it being the Alternator. I checked all the connections and they are in great shape. It seems to start acting up after the engine warms up too, maybe after about 10 minutes of highway driving. I've driven over bumps to see if there is any change at all but it doesn't seem to be related to poor contact anywhere. I've e-mailed DC Power 3 times now but I'm still waiting for a response from them.

 

Finally got a hold of them and they're sending me a new one. Sounds like it was the regulator. Thanks for the input people.