Restoring Rusty

[Gregski]

Originally Posted by texxxan

I'm glad to see that Rusty is getting some love.

yup, me too, but he's been a little shiet lately

[Gregski]

EUREKA !!! I finally figured out my left side marker (parking light) problem. FOUR YEARS later.

[texxxan]

Originally Posted by Gregski

EUREKA !!! I finally figured out my left side marker (parking light) problem. FOUR YEARS later.

Do tell...

[Gregski]

Originally Posted by texxxan

Do tell...

ha ha, short answer: bad (yet fully functional) sister parking light bulb aka the one below the headlight above the bumper!?

full report @ 11:00

[Gregski]

so basically in order to fix this Parking Light

[Gregski]

... we had to replace a perfectly good in working order light bulb in this Parking Light

We will just file this repair in our "I hit myself in the head with a hammer cause it feels good when I stop" folder and collectively move on.

[Gregski]

Wait, what? Inquiring minds want to know how I fingered it out?

Alright, after all you are under quarantine, or as I like to call it a captive audience, ha ha

so on a serious note I want to share what I went through because it can actually help somebody out and maybe knock off a year or two off the time it takes to fix this, ha ha

Here's how I went about it. I wanted to figure how these lights worked and not just hack at it until it worked.

The first thing you need to do is figure out how a component works, in this case what each wire does. This was simple enough as the pig tail in question only had two pig tails, a light blue wire and a brown wire.

Now here's a Top Tip: when trying to figure out how something works, doing so when it is broken is definitely not the time to do it. Lucky for us we had another turn signal / marker just like this one on the other side in working order, so we employed our Stare and Compare methodology.

this allowed us to quickly pick up on the fact that although each light had a different color blue wire (drive side light blue, passenger side dark blue) they each shared the same brown wire, this allowed us to Divide and Conquer even further.

[Gregski]

since the turn signals were working we focused on the brown wire, to simplicate things even further and eliminate the fuse panel and the light switch, I removed the bulk head connector off the firewall and alligator cliped a power lead from the battery positive terminal directly to the brown wire pin on the back side of the bulkhead connector - and watched three of the four marker lights illuminate

[Gregski]

after poking and probing with a test light and things not making sense I decided to yank the front marker light (the one below the headlight) and stare at it

this one made sense, in addition to the brown wire which we know sends the parking light signal, and the light blue wire which is the left turn signal signal (ha ha) it had a third wire, unlike the side marker light, it had a black wire which was the GROUND! now that makes sense color wires send the +++++ pluseses and the GROUND carries the ----- minuses (I know that's not how electricity actually flows, so please don't call the Electrode Police on me just yet I is just explaining things)

so how the hewk does our little guy in the fender get it's ground? he don't have a metal housing so it cant be contact with the sheet metal

[Gregski]

why it has to be getting it's ground through the light blue wire somehow, there is no other choice

so I poked at it some more with my test light and nothing, so once again I went to the working side and sure enough with the test light alligator clip connected to the battery positive terminal when I poked at the dark blue wire connector inside the socket it acted as a ground and the test light lit up

so back I went to the bad side and hooked up a long black wire lead from the battery negative terminal to an exposed section of the light blue wire at a Y junction as a temporary bypass and sure enough the side marker parking light came on - SAY WHAT?

I know right it don't make no sense, but now we knew how to make it work so lets press on

[Gregski]

so here's what we knew at this point

1. both side and front left marker lights need a ground to function

2. the front market light has a black ground wire the side marker light does not

so how do we send a ground signal from the front market light with the ground wire to the side marker light?

answer: via the stinkin' light bulb

somehow in some way the light bulb takes the ground signal from the front marker light and shares it with the side marker light via the light blue wire (I honestly still don't understand this magic, but I accept it)

I also do not comprehend why a good working light bulb was insufficient to send the ground signal, but a different one of the same model number was

I even cleaned it thinking it was dirty contacts and no dice, when I moved the bulb from the working side to the non working side it would work, when I went the other way it would not, luckily I found another working bulb in my stash

pic of a bulb that would not work though it matched the working bulb exactly, this is the one I cleaned the contacts on after taking the pic

[daddyjeep]

Gee.... I wonder why it took you 4 years to figure out. The solution was clear as mud.

[moregrip]

Impressive, nice work; I'll definitely try and hold on to this gem in my memory bank!

[Wgesnerjr]

If I remember correctly, the side marker and the front signal flash in an alternating pattern, right?

If so, I would think the side marker gets its ground from the front signal bulb when it is NOT activated. Therefore is lit when parking lights/headlights are on giving power to the side marker and ground thru the Front signal bulb.

When front signal is activated, the ground goes to the front signal bulb to light it and stops at the side marker. Therefore alternating the flash. Side, Front, Side Front, etc.

[Gregski]

Originally Posted by Wgesnerjr

If I remember correctly, the side marker and the front signal flash in an alternating pattern, right?.

Interesting, I just went out and tested it on my '74 and nope, they dingle at the same time. The light blue wire simply has a Y splice and one end goes to the side marker and the other to the front marker. Same deal on the other side but its a dark blue wire.

[truckin 79]

I think the ground for lights are right at radiator support or was that the Trans Am. I am pretty sure the grounds are right under the where the fender attaches.

[Gregski]

Originally Posted by truckin 79

I think the ground for lights are right at radiator support or was that the Trans Am. I am pretty sure the grounds are right under the where the fender attaches.

Correct but those grounds go to the front marker lights, there are no black ground wires going to the side marker lights.

[Wgesnerjr]

Originally Posted by Gregski

Interesting, I just went out and tested it on my '74 and nope, they dingle at the same time. The light blue wire simply has a Y splice and one end goes to the side marker and the other to the front marker. Same deal on the other side but its a dark blue wire.

So I am "working" from home today and looked at my 85. They do flash together. I don't remember where I saw the alternating thing.

I also tested the turn-signal flasher has 2 prongs and it has 12 volts power on one side and, when activated, will flash 12 volts power to the other side. seems like there would have to be a full time ground somewhere.

[hatzie]

The factory wiring makes the side markers alternate with the front turns.

[Gregski]

Originally Posted by hatzie

The factory wiring makes the side markers alternate with the front turns.

thanks, wish you had some squares to go out and test it for yourself like Jay and I did, question for you: are the front marker lights wired to both the turn signal switch (via the light and dark blue wires) and the headlight switch (via the brown wire) or just one or the other?

[hatzie]

The side marker grounds through the signal lamp except when the signal lamp is powered.
Light Blue is LH Turn power
Dark Blue is RH Turn power
Brown is Parking lamp power

The peanut bulbs in the side markers are connected from one of the blue wires to a brown wire.
The 1157 bulb is the only one that's connected directly to a ground.

It's behavior is more complex than I stated originally.

The side marker and front turns alternate when the parking lamps are on.
They operate in sync when they are off.

The 168 peanut bulb in the side marker lamp actually has two hot leads when the turns and parking lamps are powered so it shuts off.
When the turnsignal flasher is in the off part of its' cycle or just plain off there's a path to ground through the turnsignal filament so the side marker bulb lights.

Slick way to get a single filament bulb and two wires to do the job of a two filament bulb with three wires.

[Gregski]

Originally Posted by hatzie

The side marker and front turns alternate when the parking lamps are on. They operate in sync when they are off.

Ah, confirmed! thank you so much Hatzie. I recon Jay was right after all, it all depends on the condition, ha ha.

[Gregski]

Originally Posted by hatzie

The 168 peanut bulb in the side marker lamp

Whoa! don't you mean the 194?

[Gregski]

Originally Posted by hatzie

Slick way to get a single filament bulb and two wires to do the job of a two filament bulb with three wires.

Agree from the engineering perspective, totally disagree from the user perspective, ha ha! troubleshooting this was a nightmare!

[hatzie]

194 168 are the same size glass envelope peanut bulb.
168 is actually higher wattage more light. I assumed that was the bulb in use in that socket.
I'd have to look at a 73-86 CK bulb chart to be sure which one is used there.