lighting issues

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Oct 23, 2019 | 11:09 PM

Kerby76

Thread Starter

Junior User

Joined: Apr 2019

Posts: 53

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From: Gilbert AZ

lighting issues

So I have some weird things going on with my 77 F250 head lights and turn signals (fronts).

Pass side
1. front marker comes on but no turn signal
2. low beam out but high beam is good
Driver side
1. marker doesn't work but signal does
2. low beam works but no high

all bulbs are good, I checked connections (ground and power) they all work a few weeks ago
so weird thing is each side is a mirror opposite of the other
I am not sure what to do next and of course my little daily beater lost it's transmission this week and while I decide if it is worth fixing I need to drive the truck to work so headlights and turn signals would be nice
thanks for any help

Oct 24, 2019 | 07:10 AM

77&79F250

Moderator & parts slinger

Joined: Feb 2007

Posts: 50,132

Likes: 5,777

From: S/W Missouri, Polk county

Again, ck fuses, all cab and motor to firewall grounds and all connections. Dielectric grease is you friend to keep corrosion at bay. Try swapping the headlights to see if the problem is still there with know good bulbs. Things that are tied to the headlights...headlight switch, dimmer switch, t/s switch. Have you replaced any of those lately?

Turning signal and hazard flasher troubleshooting https://www.ford-trucks.com/forums/1...l#post18338355

Oct 24, 2019 | 07:24 AM

Tedster9

Post Fiend

Joined: Apr 2002

Posts: 19,311

Likes: 97

From: Waterloo, Iowa

Keep in mind the ground path goes through the radiator support, bolted to frame, wiring through to the firewall, solenoid, the floor switch, back out to the lights, etc. Poor ground paths, loose or missing straps and stuff starts getting goofy. They search for a ground through unlit bulb filaments, things like that. If any of the starting and battery ground straps or cables are original or even just kinda old they should be replaced. There might be a strap from a starter bolt to the frame, make sure this is clean and tight down to shiny bare metal. Coat it with something, vaseline, NO-OX, etc.

Oct 24, 2019 | 07:39 AM

77&79F250

Moderator & parts slinger

Joined: Feb 2007

Posts: 50,132

Likes: 5,777

From: S/W Missouri, Polk county

And a fellow FTE members great idea on added grounds. I like it!

Oct 24, 2019 | 07:59 AM

alans77crew

Laughing Gas

Joined: Dec 2004

Posts: 754

Likes: 3

From: Idaho

I always go battery to frame frame to core support then frame to engine and then engine to fire wall, and if your truck doesn't have them star washer's on all ground connection's especially the one's that ground your headlight's and turn and marker light on the core support

Oct 24, 2019 | 09:40 AM

Kerby76

Thread Starter

Junior User

Joined: Apr 2019

Posts: 53

Likes: 0

From: Gilbert AZ

I will check grounds (all of them this time). I will start checking out the switches. I think I need to attack the high/low beam and the turn signals has two different issues. Maybe check grounds first then concentrate on the turn signals first. I had swapped the grille out in May to a correct 77 from the 79 one when I bought the truck in Feb. but everything worked after the swap.
Thanks for all the advise

Oct 26, 2019 | 12:10 AM

Mitch Huested

Cross-Country

Joined: Oct 2019

Posts: 85

Likes: 1

Your last post was the key for me. they all worked in May? It sounds like a corrosion problem. As was said previously, check all your ground connections. That means unbolting them too! Ground straps are hardly what one would call "close tolerance" holes, so check that you don't have corrosion IN the bolt hole(s) of each ground. Check the hi/low beam control, but a good choice is replace when anything gets hinky. They moved them off the floor for a reason. Wet shoes, moisture, snow, etc. gets to them and they become a magnet for corrosion. Having the same problems with my 77. Time and attention to detail are all that's needed. EC 3 electrical grease is also a good purchase for your work, so you won't be doing this again in 6 months.