Issue with Lights
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Issue with Lights
So I recently bought a 1997 7.3l F250. It is in fairly good condition, but it has some problems with the lights working. The turn signals and hazards all work, as do the tail lights and headlights. However, when I hit the high beam switch, the headlights cut off entirely. Also, the brake lights do not work at all. Ive checked the bulbs and since they all work Im not sure what the issue is.
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Joined: Jan 2001
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From: Virginia
First get a testlight. Turn the highbeams on and see if you have voltage to the bulb sockets. If you don't, check the fuses, during that time period they started to fuse the highbeam lights, usually in the underhood fuse box. If that is a deadend, the switch on the column is the next place to check.
For the brake lights get under the dash on the pedal and probe the lightgreen wire on the brake switch. One side should be hot all the time, the other side should be hot when you press the pedal. If you get no voltage at all, then check the fuse. If that is all working, the next stop if the column and the signal switch.
For the brake lights get under the dash on the pedal and probe the lightgreen wire on the brake switch. One side should be hot all the time, the other side should be hot when you press the pedal. If you get no voltage at all, then check the fuse. If that is all working, the next stop if the column and the signal switch.
More Turbo
Joined: May 2014
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In addition to Franklin2's suggestions, examine the ground for both headlights and the brake lights. Highbeams draw more current than lowbeam, so they bring out weaknesses in the circuit easier. On my 97 Expedition, the headlight grounds were in abysmal condition, which i suspect led to killing the dimmer switch due to overwork. Cleaned the grounds up, replaced the switch ($12 from Rock Auto's bargain bin!) and retrofitted relays to prevent it from happening again.
Hotshot
Joined: Jan 2004
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From: St Louis
Treat the brake lamps and high beams separately. Their circuits are completely separate.
High beams - Did you check fuse F16 first? It supplies power to the high beam circuit.
When the high beams are switch on, the low beams are supposed to switch off. If the high beams aren't working, then you will have ZERO headlights with the MFS in the HIGH position.
Did you check the flash-to-pass (FTP) feature? That feature activates BOTH the low and high beams at the same time.
It is highly unlikely that the high beam issue is a grounding problem. The difference in current draw is not consequential enough to cause a complete failure in high-beam-only mode. It's most likely a fuse or the MFS unless you happen to have autolamps, then the circuit is more complex.
Actually, that would under-work the switch's contacts... bad ground = higher resistance =LOWER current = less work.
High beams - Did you check fuse F16 first? It supplies power to the high beam circuit.
When the high beams are switch on, the low beams are supposed to switch off. If the high beams aren't working, then you will have ZERO headlights with the MFS in the HIGH position.
Did you check the flash-to-pass (FTP) feature? That feature activates BOTH the low and high beams at the same time.
It is highly unlikely that the high beam issue is a grounding problem. The difference in current draw is not consequential enough to cause a complete failure in high-beam-only mode. It's most likely a fuse or the MFS unless you happen to have autolamps, then the circuit is more complex.
the headlight grounds were in abysmal condition, which i suspect led to killing the dimmer switch due to overwork.
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