Headlight going dim

[Ole BlackBetty]

I drive my truck mostly at night and have noticed when I first take off in it to drive, when it hits about 30 - 35 mph, just as it is shifting into third gear, auto trans, the head lights and marker light dim for just a second. It only does this once, from a just started engine. It does not do it every time it shifts to third. Anyone ever have this happen or have any thoughts on the matter? I do have running board lights, marker lights on cab and fenders and it is carrying my overhead camper, which has 14 marker lights, and an extra set of tail lights.

 

[riotwarrior]

Perhaps overloading system?

You didn't mention if you have all those extra lights on a relay?

How about a relay mod for the headlight themselves? Remove the load from switch...Same for marker lights...

Sounds pecuilar to me but I don't really have nuff info to say much..

 

[RLDSL]

In case you are wondering WHY he has said to remove the load from the switch and put it on a relay, these things ALL at some time or another will roast a headlight switch, and if there is too much draw going through at the time, you may end up with a cab fire. I bet if you look at the headlight switch right now , you will find one or more roasted contacts that are building resistance.
You can get a replacement switch, and plug with harness, and while you are at it, think real hard about replacing the combination turn signal, dimmer switch and plug/ harness as it gets the same load and will be in the same shape, and then while doing all this fun stuff, put all those extra lights on separate circuits run off relays and run the headlights off relays( search the site, theres plenty of info) your headlights will get much brighter, right now the factory has all of those lights including the headlights runing through a couple of single 16 ga wires

 

[riotwarrior]

Thanks Robert, I suppose I shoulda actually said that...rofl...MY Bad! I know better.....I was kinda fishing for more info...rofl

 

[RLDSL]

Thanks Robert, I suppose I shoulda actually said that...rofl...MY Bad! I know better.....I was kinda fishing for more info...rofl

Strike it up to finger fatigue

 

[Ole BlackBetty]

Ok, if this is the case, then why does it only do it one time from a cold engine? If I stop at a store on the way to where I am driving and kill the engine , turn off lights, when I come back to truck a few minutes later and start up and head on down the road, it does not do it again. it only happens when i start out with a cold engine and when it just shifts into 3rd gear the first time.

 

[RLDSL]

Ok, if this is the case, then why does it only do it one time from a cold engine? If I stop at a store on the way to where I am driving and kill the engine , turn off lights, when I come back to truck a few minutes later and start up and head on down the road, it does not do it again. it only happens when i start out with a cold engine and when it just shifts into 3rd gear the first time.

It kind of sounds to me like you may be someone who hits the key and then throws it straight into gear . Am I right so far?
If this is teh case, the glow plugs continue to cycle for a while after the engine starts , drawing extra current, and in many cases the rpms havent gone up high enough to excite the alternator enough to get it to actually start charging yet, so it will be in a hard drain condition at first until the thing gets up to rpms , and the glow plugs stop cycling , then the current in the system suddenly rises and your lights will brighten

 

[Ole BlackBetty]

I will admit that, once the WTS light goes out , I start the truck and get moving on down the road, but the lights don't brighten, they they just go dim for a split second and then come back to normal.

 

[chvycmnslvr68]

could be a bad ground somewhere .. add a ground from cab to frame to engine .... sometimes ground can be temp sensitive and hense go away after it warms up just a bit ... I have found that in most cases when electricity acts in a perculiar way it is almost always ground ...

 

[GOOSE]

I will admit that, once the WTS light goes out , I start the truck and get moving on down the road, but the lights don't brighten, they they just go dim for a split second and then come back to normal.

When your engine is cold, the gp controller will cycle the gp's to avoid excessive smoke upon warm up. This would cause the dimming for a second condition you describe. This coinciding with your third gear shift seem like it would be very difficult to duplicate every time. Doing the relay mod for your headlights would alleviate this problem but would not satisfy your thirst as to why it is happening in the first place. Could a solenoid pack in the trans draw enough current to cause this predicament?

 

[Hardass559]

injection pump cold timing advance thing is probly kicking off when it gets to third gear