Bright lights flickering
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Postmaster
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From: SE Georgia
Bright lights flickering
This is in my 79 Bronco, so I am posting here since this is pretty much the same as the 77-79 F series.
I installed some of the H4 headlights on my Bronco Bronce back. I also installed a 3G alternator as well. My low lights are working fine, but when I turn on the bright lights...the lights are flickering bad.
What could be causing this?
My alternator is reading 13-14v as usally.
I installed some of the H4 headlights on my Bronco Bronce back. I also installed a 3G alternator as well. My low lights are working fine, but when I turn on the bright lights...the lights are flickering bad.
What could be causing this?
My alternator is reading 13-14v as usally.
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Postmaster
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From: SE Georgia
I just tried to turn on the headlights while the truck is off. They never came on. They usually did before. I swapped the 30a relays around now. The dims came on but brights didn't. I clicked back to dim and no lights now. The voltage stayed around 13-14 v during this. I kept playing with the headlight switch and the dims came back on a couple or time and now no headlights are coming on. The running lights and tail lights are working fine.
I am wondering if it is some bad relays? I just swapped out the headlight switch on the floor awhile back
I am wondering if it is some bad relays? I just swapped out the headlight switch on the floor awhile back
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I’m having an issue with my headlights too in my 76 F150. When I click the floor switch, instead of toggling between bright and dim, it toggles between on and off. I’m about half-way through reading a book about automotive wiring so if I figure out how to diagnose and fix the issue I’m having, I’ll come back and post something. Seems like the wiring gurus that used to answer these types of questions are not around lately.
Moderator & parts slinger
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FTE talk on the LED conversion.
https://www.ford-trucks.com/forums/1...+light+install
https://www.ford-trucks.com/forums/1...+light+install
https://www.ford-trucks.com/forums/1...+light+install
https://www.ford-trucks.com/forums/1...+light+install
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I thought the OP was talking about halogen bulbs, in which case doing the headlight “relay upgrade” would probably solve the problem. Here’s a plug and play kit for that: https://ceautoelectricsupply.com/pro...ht-relay-kits/
or you can make your own headlight relay harness. It’s supposed to take the stress off your 40 year old wiring. If you are using LED, they really should have come with those anti-flicker “Canbus” things. I just bought a set of LED headlights off eBay for $70 and they came with. But my problem is not flicker, it’s that either low beams or high beams don’t come on at all. Either way, the first place to start I think is checking voltage drops at various points of the headlight circuit which I will attempt today.
or you can make your own headlight relay harness. It’s supposed to take the stress off your 40 year old wiring. If you are using LED, they really should have come with those anti-flicker “Canbus” things. I just bought a set of LED headlights off eBay for $70 and they came with. But my problem is not flicker, it’s that either low beams or high beams don’t come on at all. Either way, the first place to start I think is checking voltage drops at various points of the headlight circuit which I will attempt today.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
I thought the OP was talking about halogen bulbs, in which case doing the headlight “relay upgrade” would probably solve the problem. Here’s a plug and play kit for that: https://ceautoelectricsupply.com/pro...ht-relay-kits/
He needs to post up just what he has in his head light system to help better.
Dave ----
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FTE Legend
Joined: Nov 2015
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From: Angier, NC
I’m having an issue with my headlights too in my 76 F150. When I click the floor switch, instead of toggling between bright and dim, it toggles between on and off. I’m about half-way through reading a book about automotive wiring so if I figure out how to diagnose and fix the issue I’m having, I’ll come back and post something. Seems like the wiring gurus that used to answer these types of questions are not around lately.
Head light switch has power to it all the time and has a breaker (re-set-able fuse).
When you pull on the head lights power comes out and is sent to the floor dimmer switch.
Power is then set to the head lights either low beams and a push of the switch the high beams.
So if you have 1 set of lights (high or low) and not the other it can only be 2 things.
Bad dimmer floor switch or bad bulbs.
Easy check with a test light to see what you have at floor switch. should have power in with head lights turned on and power out on 1 wire.
Push the switch and you should have power out on the other wire. If not bad switch.
Can do the same out at the lights.
1 wire is a ground, 1 wire low beam & the other high beam. If that checks out then has to be a bad bulb.
Bulbs should be replaced in pairs as they have the same run time and can burn out at the same time.
Dave ----
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Postmaster
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From: SE Georgia
I have the H4 headlight conversion from Jeffs Bronco Graveyard.
It has two 30 Amp relays for the low and high beam. I just ordered some 40 Amp relays.
The dim lights came back on last night so I limped it home. I stopped at a store and was fixing to leave and the lights didnt come back on. I kept pushing in and out the headlight switch and the dim lights came back on
It has two 30 Amp relays for the low and high beam. I just ordered some 40 Amp relays.
The dim lights came back on last night so I limped it home. I stopped at a store and was fixing to leave and the lights didnt come back on. I kept pushing in and out the headlight switch and the dim lights came back on
Lead Driver
Joined: Jul 2017
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From: San Jose, CA
In the meantime if you have to drive at night you can unplug one headlight and run just on the one remaining. If it's just an overload situation (even with relays it still could be, if the relays are faulty) then halving the load should at least get you temporarily back on the road.
But it sounds like the new relays are defective. If they're the same style we use then they are slightly different from the most typical relays. So make sure you order the right style.
If they're square blocks then they're likely the standard "Bosch Type" setup. If they're "flatter" for lack of a better description, then they are still a common type, but not the style most people think of.
Good luck. Hopefully it's just a relay thing and not something more insidious in the wiring.
And frankly, if it's the relays (and they're not that old) I would ask Jeff's for a replacement set. Then you can keep those as spares just in case.
Paul
But it sounds like the new relays are defective. If they're the same style we use then they are slightly different from the most typical relays. So make sure you order the right style.
If they're square blocks then they're likely the standard "Bosch Type" setup. If they're "flatter" for lack of a better description, then they are still a common type, but not the style most people think of.
Good luck. Hopefully it's just a relay thing and not something more insidious in the wiring.
And frankly, if it's the relays (and they're not that old) I would ask Jeff's for a replacement set. Then you can keep those as spares just in case.
Paul
Fleet Mechanic
Joined: Jul 2017
Posts: 1,276
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From: KY
I have the H4 headlight conversion from Jeffs Bronco Graveyard.
It has two 30 Amp relays for the low and high beam. I just ordered some 40 Amp relays.
The dim lights came back on last night so I limped it home. I stopped at a store and was fixing to leave and the lights didnt come back on. I kept pushing in and out the headlight switch and the dim lights came back on
It has two 30 Amp relays for the low and high beam. I just ordered some 40 Amp relays.
The dim lights came back on last night so I limped it home. I stopped at a store and was fixing to leave and the lights didnt come back on. I kept pushing in and out the headlight switch and the dim lights came back on
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Postmaster
Joined: Nov 2009
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From: SE Georgia
Well, I am fixing to head home and I just turned on the lights. The dims and highs are working now. Weird. But if i switch to the high and rev up my engine...the high beams starts to flicker. The low beams don't. I am wondering if it is my alternators regulator 🤔
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Ok a quick run down of your system.
Head light switch has power to it all the time and has a breaker (re-set-able fuse).
When you pull on the head lights power comes out and is sent to the floor dimmer switch.
Power is then set to the head lights either low beams and a push of the switch the high beams.
So if you have 1 set of lights (high or low) and not the other it can only be 2 things.
Bad dimmer floor switch or bad bulbs.
Easy check with a test light to see what you have at floor switch. should have power in with head lights turned on and power out on 1 wire.
Push the switch and you should have power out on the other wire. If not bad switch.
Can do the same out at the lights.
1 wire is a ground, 1 wire low beam & the other high beam. If that checks out then has to be a bad bulb.
Bulbs should be replaced in pairs as they have the same run time and can burn out at the same time.
Dave ----
Head light switch has power to it all the time and has a breaker (re-set-able fuse).
When you pull on the head lights power comes out and is sent to the floor dimmer switch.
Power is then set to the head lights either low beams and a push of the switch the high beams.
So if you have 1 set of lights (high or low) and not the other it can only be 2 things.
Bad dimmer floor switch or bad bulbs.
Easy check with a test light to see what you have at floor switch. should have power in with head lights turned on and power out on 1 wire.
Push the switch and you should have power out on the other wire. If not bad switch.
Can do the same out at the lights.
1 wire is a ground, 1 wire low beam & the other high beam. If that checks out then has to be a bad bulb.
Bulbs should be replaced in pairs as they have the same run time and can burn out at the same time.
Dave ----
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Postmaster
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From: SE Georgia
Verdict.
I had a bad corroded headlight plug near the radiator support. Installed a new one. No flickering! Also had a wire unplugged from my alternator...i hooked it up but it had nothing to do with it. It was the S terminal.
Thank God it wasn't nothing that'll cost me alot of $$.
I had a bad corroded headlight plug near the radiator support. Installed a new one. No flickering! Also had a wire unplugged from my alternator...i hooked it up but it had nothing to do with it. It was the S terminal.
Thank God it wasn't nothing that'll cost me alot of $$.
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