Lights gremlins!
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Elder User
Joined: May 2008
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Lights gremlins!
OK, after pulling my instrument panel to replace a couple of the small 194 bulbs (and not plugging the instrument panel connector back in for couple of weeks), I put everything back together. Here's what happened. I pulled the light switch on (parking lights). The exterior lights all came on, but no instrument panel lights. When I pulled the light switch all the way out, I get no headlights. Rotating the instrument panel dimmer switch didn't help either. Now I know I have a very weak battery (lights are weak and also the truck won't start), but is this a symptom of battery, or light switch, typically?
Posting Guru
Joined: Sep 2009
Posts: 1,159
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From: Suburbs of Chicago
Well if your battery is low enough it might not have enough for the current(amperage) demand of the headlights.
Did you maybe blow a fuse for your I/P lights?
You really need to take care of your battery before you can start condemning other electrical components.
Did you maybe blow a fuse for your I/P lights?
You really need to take care of your battery before you can start condemning other electrical components.
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Elder User
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Here's the deal with fresh battery:
Exterior lights work properly.
Turn signal lights work properly.
No other instrument panel lights work: the two general lights nor the high beam nor the brake light (when I connect a jumper at the plug).
The headlights work, but at only one setting - I haven't figured out if they work on low or high).
Lastly, my dome light comes on when door opens but not when I rotate the headlamp switch counterclockwise.
Ideas??
Exterior lights work properly.
Turn signal lights work properly.
No other instrument panel lights work: the two general lights nor the high beam nor the brake light (when I connect a jumper at the plug).
The headlights work, but at only one setting - I haven't figured out if they work on low or high).
Lastly, my dome light comes on when door opens but not when I rotate the headlamp switch counterclockwise.
Ideas??
Senior User
Joined: Feb 2013
Posts: 266
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From: Idaho
sounds like your headlight switch may be bad...it controls the brightness of the dash lights and dome light. Although you may not be able to see the dash lights in daylight hours...I cant see mine light up. But at night they are visible. Your high beam switch may or may not be bad depending if they switch over or not. Both are an easy fix...if that fixes your problem.
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Elder User
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sounds like your headlight switch may be bad...it controls the brightness of the dash lights and dome light. Although you may not be able to see the dash lights in daylight hours...I cant see mine light up. But at night they are visible. Your high beam switch may or may not be bad depending if they switch over or not. Both are an easy fix...if that fixes your problem.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
With the headlight switch pulled out to either stop and the **** turned all the way counter-clockwise, check for power on both sides of the dash illumination fuse. You need to identify where power is dropping out. If you've already checked the fuse, please explain what you actually did (don't just say it's fine).
The dome light / headlight switch issue sounds like an issue with the headlight switch or the wiring to it.
The brake warning switch will not come on just by jumping the two terminals in the plug. It's a ground-out switch. To get it to come on, you would jump the two terminals in the plug, then pull that common point to ground. The reason for two terminals in the plug is to prevent bypassing the prove-out safety mechanism.
The dome light / headlight switch issue sounds like an issue with the headlight switch or the wiring to it.
The brake warning switch will not come on just by jumping the two terminals in the plug. It's a ground-out switch. To get it to come on, you would jump the two terminals in the plug, then pull that common point to ground. The reason for two terminals in the plug is to prevent bypassing the prove-out safety mechanism.
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Elder User
Joined: May 2008
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With the headlight switch pulled out to either stop and the **** turned all the way counter-clockwise, check for power on both sides of the dash illumination fuse. You need to identify where power is dropping out. If you've already checked the fuse, please explain what you actually did (don't just say it's fine).
The dome light / headlight switch issue sounds like an issue with the headlight switch or the wiring to it.
The brake warning switch will not come on just by jumping the two terminals in the plug. It's a ground-out switch. To get it to come on, you would jump the two terminals in the plug, then pull that common point to ground. The reason for two terminals in the plug is to prevent bypassing the prove-out safety mechanism.
The dome light / headlight switch issue sounds like an issue with the headlight switch or the wiring to it.
The brake warning switch will not come on just by jumping the two terminals in the plug. It's a ground-out switch. To get it to come on, you would jump the two terminals in the plug, then pull that common point to ground. The reason for two terminals in the plug is to prevent bypassing the prove-out safety mechanism.
And another observation - back a month ago my dash lights were working, but were acting up. I had to jiggle the rheostat **** from full dim to full bright to get the damn things to come on. Now, after unplugging both speedometer cable and main wiring connector from back of IP (for replacement of 194 bulbs), there's no lights at all.
Last edited by alchemist1; Mar 4, 2013 at 03:15 PM. Reason: update
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Elder User
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Just checked brake light and it does work! gonna pull my good headlight switch from my 77 and will put in the 74.
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Elder User
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one more question (sorry). should there be an ash tray light on the 74 F100? my 77 didn't have one, so not sure. Also, my high beam indicator light isn't coming on. is that typically a bad high beam switch (the switch is flaky, it sometimes cuts out the low beams and you have to push it off/on a couple of times to get the low beams to stay on)??
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
That's a good question on the ash tray; I'll have to defer to someone else (it was an options on sedans).
The high beam indicator can be a bad high beam switch, bad wiring, bad bulb, corroded contacts...anything to keep the light from coming on. You already need to replace the high beam switch because it's cutting off your low beams, so fix that first and see what's left over for you to deal with.
The high beam indicator can be a bad high beam switch, bad wiring, bad bulb, corroded contacts...anything to keep the light from coming on. You already need to replace the high beam switch because it's cutting off your low beams, so fix that first and see what's left over for you to deal with.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
What are you talking about? I have no idea what you're saying. Are you trying to say that the headlights and running lights can't be on at the same time? That's incorrect. If that were true, there would be no way for the tail lights to be on when the headlights are on. Your post is missing a bunch of words and doesn't make any sense.
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Elder User
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What are you talking about? I have no idea what you're saying. Are you trying to say that the headlights and running lights can't be on at the same time? That's incorrect. If that were true, there would be no way for the tail lights to be on when the headlights are on. Your post is missing a bunch of words and doesn't make any sense.
sorry, couldn't resist! looks like jibberish