Ok coming home to night I stop at the gas station for my wife to run in and get some water, My lights were shining on the building and I noticed that they would go back and forth getting really dim and then brightening back up to normal low beams. When I would raise the RPM's they would dim and stay dimmed, so when I got home I popped the hood kinda thinking I might have a bad connection( I PUT THE HD LIGHT HARNESS ON ABOUT 4 MONTHS AGO NO PROBLEMS WITH IT) So I thought maybe I had a loose connection.....nothing. When I turn the truck off and leave the lights on they have normal brightness, with it running ONLY!! the head lights dim NOTHING ELSE!!

Any thoughts???

Sat. morning my truck had a dead battery so I put the charger on it and fired it up, is it possible that the alternator is causing this or is there a more SINISTER reason??

Thanks Chris

 

You're aware that when the grids cycle your lights will dim? I'll bet it's cold up there in Montana this weekend, so your grids are constantly cycling.

 

Big Blue24 is wise.
These darn trucks like cycleing the grids.
My lights do the same thing. When you rev the engine over 1k, it will start charging the battery and dim the lights agian.
To me, what you are seeing is normal.

JD

 

No it's not that I am fully aware of the cycling issue with the heater grid this is completely different. Heck when the grid cycles it pulls the voltage down a bit, when the lights dim on my truck right now the gauge never drops one bitAnd it is only in the headlights no where else not the parking, cab or tail lights.


Thank you though it's appreciated!

 

Sounds right except for the dead battery.

 

What sounds right??


I believe the dead bat. was caused from me hooking some thing up that pulled direct current from the bat all night

 

I would get to a shop and get them to do a load test on the batteries. If the batteries are very low that would cause the problem.

 

That was my other thought if the bat. is very low can you charge them back up or are they gonna be garbage now? Shoot the bats. are less than a year old!

 

Yup, you can kill batteries fast when it is cold and they are dead. Charging them will only work to a point, if they are past the point of no return they are done for.

 

Did you just change your oil if so check the fuse for your alt.
There is a terminal next to your oil filter and if you jumper across it with an oil filter wrench it will blow the fuse. Then when your grids surge the voltage comes straight off the batt and will cause the batt to go Dead.

 

I changed it about 3wks ago so I can't imagine it's that. Thanks though

 

Good tip, might help some other guys out as well.

 

Are your terminals spic and span clean? I've had stranger things happen when my terminals/connections were dirty and or corroded.

I figured you were well aware of the grid heater cycling but just threw it out there to eliminate that part of the equation.

 

Your alt has an internal Voltage regulator wich may also be going out I would have it tested

 

These are all good suggestions I will be going by a place tomorrow so I will have them check both my bats. and the alternator.

No prob. BigBlue it's best to clear up the obvious right away otherwise you end up pissing in the wind!