No headlights

SkipBurney

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Well I let my 89 sit for about 2 years and when I drug it out to replace glow plugs and injectors and get it back on the road I have no headlights. I have all of the others just no headlights. Pulled the dimmer switch and cleaned everything up and still no headlights. Got a new dimmer switch and still no headlights. All of the fuses I checked are good but the fuse panel dosent show a dedicated fuse for the headlights. I have 12 volts at the dimmer switch plug. I jumped across the dimmer switch plug and still no headlights.The high beam indicator in the instrument cluster shows high beams all of the time no matter what I do with the dimmer switch. Any suggestions from anyone?
 

Selahdoor

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This may sound dumb, but have you checked the headlight bulbs?

Were I you, I'd start there, and work my way backward to the headlight switch.

Get a wiring diagram to see everything that is between the headlights and the headlight switch.
 

SkipBurney

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This may sound dumb, but have you checked the headlight bulbs?

Were I you, I'd start there, and work my way backward to the headlight switch.

Get a wiring diagram to see everything that is between the headlights and the headlight switch.

Both bulbs are good I went there after the fuses, the center terminal on the dimmer switch has 12 volts on it and the center terminal on the headlight plugs have 12 volts on them. Does anyone know if these trucks have headlight relays on them
 

Selahdoor

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They do not.

The problem with the headlight setup is that the headlight switch and it's connector burn up. Since power has to come from the battery, to the headlight switch, then through the dimmer switch, then to the headlights.

It is so common for the headlight switch and connector to burn up... That you can buy both at... Home Depot!

Yours is sounding like you need to replace the dimmer switch.

Look up headlight relay upgrade on here.

I had to replace the headlight switch and it's connector. Then I upgraded to relays. Glad I did.



How do you know the bulbs are good?

Having voltage at one of the pins does not mean the bulbs are good.

Have you jumpered them from the battery to see if they light up?
 

SkipBurney

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Yep checked both bulbs with a meter and they read good. I have already replaced the dimmer switch because it was completely covered in corrosion and I was sure it was the problem but it wasn`t. Guess I just need to replace the headlight switch and see if that cures it. I`m guessing there must be corrosion on the switch contacts
 

Selahdoor

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Try unplugging it and plugging it back in several times. Then squeeze some dielectric grease into the connector slots, and plug it in the final time.

I'm guessing though, that you will find some burnage going on, and not just corrosion.
 

franklin2

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If you have 12v at the dimmer switch, your headlight switch is good. The headlight switch feeds the dimmer switch.

If the dimmer switch is good, you should have 12v on one of the side terminals, depending in if it's on lowbeam or highbeam mode.
 

Selahdoor

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If you have 12v at the dimmer switch, your headlight switch is good. The headlight switch feeds the dimmer switch.

If the dimmer switch is good, you should have 12v on one of the side terminals, depending in if it's on lowbeam or highbeam mode.
Been wondering how he is getting 12v at the center post at the headlights. Isn't the center one supposed to be ground?
 

franklin2

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Both bulbs are good I went there after the fuses, the center terminal on the dimmer switch has 12 volts on it and the center terminal on the headlight plugs have 12 volts on them. Does anyone know if these trucks have headlight relays on them

This is post #3. He said he had 12v on the center terminal of the dimmer switch. That is what I was going off of.

Unplugging the headlight and checking voltage on the headlight plug itself is not a good test unless you have a testlight. With the headlight unplugged and using a digital meter, it can lie to you. Always keep the plug plugged in to a good headlight and try to poke at the back of the headlight plug leaving the load (headlight) plugged in.

That is actually true for the center pin on the dimmer switch also. So there is a chance if you had it unplugged and are using a digital meter, that it is lying to you and it could be the headlight switch still. Not good practice to unplug things and check them like that.
 

SkipBurney

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LET THERE BE LIGHT! I pulled the headlight switch and there was some heat discoloration on both the plug and the old switch. I tossed the old switch and cleaned up the terminals on the plug and plugged in the new switch with a little dieelectric grease on everything and the lights work fine now. A big thanks to you guys for all of your help
 

chillman88

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Awesome! Now go pick up the relay kit from bronco graveyard and prevent the issue from returning.

No, these trucks didn't come with relays from the factory, but they definitely should have!

Glad it's working for you again!
 
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