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Left Turn Brings On "Exterior" Lights

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Gary Lewis

Left Turn Brings On "Exterior" Lights

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I've been living with a problem for some time but haven't figured it out so I'm looking for some ideas on what is wrong on Big Blue - when I signal for a left turn apparently the Brown "exterior lights" wire gets energized. That means that the following things blink:

Marker lights

Park lamps

Fog lights since they are brought on via the Br wire

Mission Control switch illumination as that's tied to the Br wire as well

My first thought was that I have something mis-wired in Mission Control, but the left-turn wires don't appear there. Then I thought about C305/A and discovered that the Br wire isn't in it. Then I looked at the turn signal switch and it doesn't have the Br wire in it. Last look was the trailer lights relay, but I don't see the LG/O wire going to that relay.

So what am I missing? Where do the turn signals and exterior lights wires go where they might be crossed?

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

ratdude747

Re: Left Turn Brings On "Exterior" Lights

I'd be looking at your left turn signal sockets... sounds like the parking/marker light circuit and the left turn signal circuit are shorted together and that's where the two circuits come close in proximity . I'm thinking either a bad splice job, a cut (and shorted) harness, something messed up in the socket, or a bad bulb with an internal short? I'd try it with the turn signal bulbs removed (and the socket cleaned/inspected to rule them out first, then look for any signs of past repairs or harness damage.

1984 F150: 300 L6, AOD, RWD. EEC IV / TFI, Feedback Carter YFA Carb. Stock everything but radio (for now).

Gary Lewis

Re: Left Turn Brings On "Exterior" Lights

Administrator

That's a good idea, Larry. I pulled the LR tail light and I'm pretty sure that's not it as the connections look good and it still does it when the bulb is bad. But I'll pull the left headlight bucket to get to that turn signal and see if something is wrong there.

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: Left Turn Brings On "Exterior" Lights

Administrator

Larry, you are THE MAN! Thanks! It was the LF turn signal bulb - an LED. The one on the bumper has some kind of a connection between the turn signal side and the marker light side. I replaced it with the one that's in the socket and the problem went away.

However, the one I put in doesn't come on with the markers. And on the other LED when I put power to one of the solder connections and ground to the other I get a spark. But when I put power to either of them and put ground on the body I get different LED's to come on.

So there's something funky going on with at least that LED, and the other one doesn't work right either, although it may be blown on the marker light side. So I'm going to replace it with an incandescent 1157 and be done with it.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Left Turn Brings On "Exterior" Lights

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I was going to say both circuits share C121, but you seem to have found it!

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Left Turn Brings On "Exterior" Lights

Administrator

Yes, it could have been that connector. But Larry's suggestion of a bad bulb caused a light to come on in my head (pun intended) as I knew I had an LED in there. And this didn't appear to be due to any of my many wiring escapades as it just started out of the blue. (Orange?

) So a shorted LED sounded very probable.

But I'm conflicted as to what to replace the bulb with since I'm out of 1157's and would like to go with an LED. However, most of the LED's I'm seeing are very similar to the one that is bad, with the exception of the SYLVANIA ZEVO 1157 Amber LED Bulbs, two of which are $20. But note that the package says For Off Road Use Only. Are they too bright?

I'm thinking of going with these. Thoughts?

Gary, AKA "Gary fellow": Profile

ratdude747

Re: Left Turn Brings On "Exterior" Lights

1. Glad you found the issue!

2. Signal/marker lights are one place I'd skip LEDs if using stock housings. The Fresnel lenses are built specifically for incandescent bulbs and the light position and pattern they produce... since the point is to be seen with such (not necessarily additional illumination for you to see with), you want the fresnel lens to do it's thing.

(When I get home I'll link in a video with more on this).

1984 F150: 300 L6, AOD, RWD. EEC IV / TFI, Feedback Carter YFA Carb. Stock everything but radio (for now).

ArdWrknTrk

Re: Left Turn Brings On "Exterior" Lights

Administrator

In reply to this post by Gary Lewis

I have the Zevo lights in my dash and reverse sockets.
No problems with them (so far!)

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Left Turn Brings On "Exterior" Lights

Administrator

In reply to this post by ratdude747

Larry - You have a good point about the lens. Daniel Stern mentioned that in his discussion of lighting. And here's a snippet from that giving his recommendation on the turn signals:

The main exterior signal lamps can safely be made 45% brighter with special high-efficiency bulbs available (only) through the Honda parts system.

The single-filament variety with a single contact in the centre of the bottom of the bulb's base (replacing 1076, 1141, 1156, P21W, P25-1, and a few others—these go in your reversing lamps) is http://www.amazon.com/dp/B00IFP9P4O/?tag=2402507-20 .

The dual-filament variety with two contacts side-by-side on the bottom of the bulb's base (replacing 1034, 1157, 2057, P21/5W, P25-2, and a few others—these go in the brake lights and front turn signals) is http://www.amazon.com/dp/B00BFDIN0K/?tag=2402507-20 . These only come in clear; if you need an amber bulb because your front turn signal lenses are also clear/colourless, use https://www.amazon.com/dp/B000IY7TGQ/?tag=2402507-20 .

But those bulbs are $15/ea. I can have a pair of the Sylvania LED's for about that. And they are oriented similarly to the incandescent bulbs, so I'm thinking about buying them and trying them out. But I would like to see the video.

Gary, AKA "Gary fellow": Profile

ratdude747

Re: Left Turn Brings On "Exterior" Lights

Not a car channel but a technology channel... this came up in the context on a video about turn signal flashers over the years:

1984 F150: 300 L6, AOD, RWD. EEC IV / TFI, Feedback Carter YFA Carb. Stock everything but radio (for now).

ArdWrknTrk

Re: Left Turn Brings On "Exterior" Lights

Administrator

Alec always has an entertaining rabbit hole to dive into! 🤓

I think I like appliances the best.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Left Turn Brings On "Exterior" Lights

Administrator

Ok, I watched both videos. And he made a really good point about the lenses being designed for an incandescent bulb - the same thing that Daniel Stern says. That, coupled with some of the reviews on Amazon about the Sylvania LED's being counterfeit makes me think I'll be better off going out and buying some good old 1157's from the parts store.

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: Left Turn Brings On "Exterior" Lights

Administrator

I stopped in to see Dewayne @ Skiatook Auto Parts and got four 1157's. I've replaced the front turn signals with them, removing the LED's, and all is well. And I checked the tail/stop lights to ensure they are running incandescent bulbs as I was trying out an LED in one at some point in the past. I thought I'd gone back to incandescent bulbs due to a problem with the trailer brake controller, but just wanted to check - I had.

So with the exception of the side marker lights I'm running all incandescents on the exterior.

Gary, AKA "Gary fellow": Profile