Headlight Power?
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Freshman User
Joined: Jan 2006
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Headlight Power?
Hello,
I have no voltage to my headlights. Is there a relay or something? It does not appear that there is a fuse in the box for the lights.
My truck is a 1989 f 150.
I do have running lights etc. just no voltage to the headlight sockets.
Thank You, ROB
I have no voltage to my headlights. Is there a relay or something? It does not appear that there is a fuse in the box for the lights.
My truck is a 1989 f 150.
I do have running lights etc. just no voltage to the headlight sockets.
Thank You, ROB
Posting Guru
Joined: Jan 2002
Posts: 1,346
Likes: 8
From: Baltimore
I'm looking at a wiring diagram for a 88 so hopefully the wire color codes are the same on a 89.
A fusible link from the battery feeds 12 volts direct to the Headlight switch via a Black/Orange wire. Since the Marker lights work, the fusible link is ok.
When you place the Headlight switch in the Head position (pulled all the way out) 12 volts goes thru the switch and out of the Switch via a Red/Yellow wire which goes to the Dimmer switch.
I believe your dimmer switch is mounted on the driver side floor. (Press with your left foot). The 12 volts goes thru the dimmer switch to light the Instrument cluster High beam indicator and High beam filament when the dimmer switch is in the High position.
If the dimmer switch is in the Low position, only the Low beam filaments will light.
So what you need to do is remove the Dimmer switch and use a volt meter to measure the voltage at the Red/Yellow wire at the Dimmer switch.
With the Headlight Switch on, you should measure 12 volts on the Red/Yellow wire.
If no 12 volts, the Headlight Switch is probably bad.
If you do measure 12 volts, with the Dimmer switch in the Low beam position, you should measure 12 volts on the Red/Black wire which goes to the Low beam filaments.
In the High beam position you should measure 12 volts on the Light Green wire which goes to the High beam filaments and Instrument Cluster High Beam indicator.
A fusible link from the battery feeds 12 volts direct to the Headlight switch via a Black/Orange wire. Since the Marker lights work, the fusible link is ok.
When you place the Headlight switch in the Head position (pulled all the way out) 12 volts goes thru the switch and out of the Switch via a Red/Yellow wire which goes to the Dimmer switch.
I believe your dimmer switch is mounted on the driver side floor. (Press with your left foot). The 12 volts goes thru the dimmer switch to light the Instrument cluster High beam indicator and High beam filament when the dimmer switch is in the High position.
If the dimmer switch is in the Low position, only the Low beam filaments will light.
So what you need to do is remove the Dimmer switch and use a volt meter to measure the voltage at the Red/Yellow wire at the Dimmer switch.
With the Headlight Switch on, you should measure 12 volts on the Red/Yellow wire.
If no 12 volts, the Headlight Switch is probably bad.
If you do measure 12 volts, with the Dimmer switch in the Low beam position, you should measure 12 volts on the Red/Black wire which goes to the Low beam filaments.
In the High beam position you should measure 12 volts on the Light Green wire which goes to the High beam filaments and Instrument Cluster High Beam indicator.
Thread Starter
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Freshman User
Joined: Jan 2006
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Wow! Like always this is a great source for information. I put my common sense hat on again and remembered the problems that I have had in the past.
I pulled up the floormat and removed the switch.
You guess it, hot in the middle.
I replaced it with a spare.........good to go.
I appreciate all of your help and guidance, ROB
I pulled up the floormat and removed the switch.
You guess it, hot in the middle.
I replaced it with a spare.........good to go.
I appreciate all of your help and guidance, ROB
