Driving along at night when all of a sudden my headlights just kinda flicker on and off - VERY scary on a pitch black country road. This happened once before about a year ago and I replaced the headlight switch. Maybe this wasn't the problem - even though it hadn't happened for a long time. Not sure what else to check. Any ideas?

 

it could well be the switch there noted for that but first go over all the connections

 

Check the grounds. They are grounded to the core support.

 

Can you tell me where to look? - I don't know what you are talking about

 

Behind each light is a three-prong plug, bright, dim, and ground.

The ground is the little black wire.

Follow it to a sheetmetal screw through the sheet-metal of the radiator-support.


Remove and wire-brush/clean both the sheet-metal and the wire-eyelet, then re-assemble.

 

I just had this issue tonight on my way home!, came here to get help and presto, someone else with my problem.
Wheelo

 

Ok - will do. But if those were the cause, wouldn't it affect individual lights? Both of mine go off at the same time - happened again tonight. All of a sudden it's PITCH BLACK. Geez - THAT will put the fear of god into you...

 

The main body ground is under the same screw as the left headlight ground. If it's flaky you're going to get a good blink.

BTW, it is a lousy design. I think they should have used 30 more inches of wire and put the main body ground on the firewall. On an old rusty rattly truck it's asking a lot to have good contact between the core support, fenders, and cab.

 

try the connection with the headlight switch, thats what my head light problem was. squeezed it together and the light turned on!!!!!!

 

To really FIX the headlight problem, look in the "sticky", and in about a thousand other places on the internet, for the "headlight relay MOD".


Do this modification, along with a thorough cleaning/inspection of EVERY connection/terminal/point-of-contact in the light system, and your light problems will disappear.

Once you see just how poor the factory light wiring system is, you will wonder that they ever worked at all.


Also, a decent set of fog/driving lights, properly switched, wired, and grounded, are a good emergency back-up, in the event that the lights do go out.

 

Maybe I can shed some LIGHT on the problem.

Did all of the lights go out or just the headlamps?

Do you have lots of lights or gauges installed on your truck?

Here is a diagram that should give you an idea of where the connections are, since you said they both went out I would think the problem would be inside the cab, that is why I ask if they ALL went out



Here is the Left side and the Bulkhead connector where the wiring enters into the cab.

If you look you can see just how frail the stock wiring really is:
Low Beam = 14-gauge.
High Beam = 16-gauge.
Ground = 20-gauge.

Now if you were to a install a set of Silver Stars and need the extra current to drive them, guess where it will not come from and then you will say “ they aren’t that much brighter that my old ones”

Now that you see this, you should now think about doing this.

https://www.dieseltruckresource.com/...d.php?t=176263



Now
If you look at the bottom right corner you will see the 14-gauge Red/Orange wire that comes through the firewall through the Bulkhead connector, this in your Low Beam headlamp wire, it will go through a 2 pole connector located above the steering column above your feet, from there it goes to the High Beam Switch (This switch might be the culprit, how many times have you yanked it up and down for the directional signals in the last 15 years) and then it gets power from the Headlamp Switch. Terminal #H through the circuit breaker and Terminal #B-1 to connection point L-1 and then to the Fusible Link back at the battery.

The reason I was asking about the lights or the gauges, if you were to add too many lights to the truck or (have a short circuit in the circuit) and tie them into the headlight circuit so they come on when you pull the switch (this could also be a trailer connector wet or packed with road salt muck yuck.)
When it starts to draw too much current the internal circuit breaker deep inside the headlight switch will open and ALL of your lights will go OUT.

If the overload is corrected it should reset but if not it will keep opening until it is corrected or a bump in the road removes the short.

Add to the age of the light switch especially if the load has been marginal for some time and it could fail at any time.

I learned the hard way in the 70’s at about 60 MPH coming down a mountain road, Headlights, dash lights went black. Luckily I had 4 Lucas Driving Lamps on also.

If you add any lamps including in the gauges, power them through Bosch Relays and your headlamp switch will last forever.

I hope this has given you something to think about.
Jim

Oh, if your truck happens to be from Canada there are a few more places to look.

How do I know if it is from Canada? The dumb headlights stay on all of the time.

 

THANKS Jim -

Only the headlamps go out - I believe it has happened with both the brights on and off. Only extra installed is a tach. No extra lights.

I just got up so I will have to read your entire post when I am fully awake, but THANK YOU.

And, of course, thanks to everyone else.

 

This post was a lifesaver. Thanks Jim Lane

 

I hate reading factory wiring diagrams... Is it just me? Just something about them that bother me.

Um, yes the grounds are a terrible design. I'm tempted to take a 2/0 wire, connect one end together on the bolt for the starter ground, and bolt the other end to the cab below the steering column with a stainless steel bolt. It really is amazing that they counted on that little 10 ga wire for everything.