[RV6]

So here I sit with another busted turn signal switch. The flashers and stop lights both work but nothing happens when signaling a lane change. This is the second switch in two years to bite the bullet. I used my trusty VOM and confirmed the switch is bad. The light dawned this morning.

I am not fond of LED brake lights. The harsh on/off is not as pleasing to me as the soft on/off of incandescent bulbs. LED brake lights are also expensive although, I could have paid for them now with three turn signal switch buys but, I digress.

In each tail light assembly in my 67 I installed Scott Drake 3 bulb inserts and with a bulb behind each lens the park and brake lights are nice and bright. I finally figured out that the 3 bulbs on each side are pulling 3 times the amps for the turn signals and 6 times the amps for the brake lights. (I’ve been through two brake light switches also).

So for each turn signal contact in the switch the rear lights pull 4.5 amps instead of the 1.5 amps of a standard 1157 bulb. The switch cannot handle this and will burn out contacts in short order. So I think I’ve come up with a solution.

My solution is to place a 12V relay in the brake/turn light circuit on both sides. I can run a dedicated hot wire to the relay for the light power and the relay itself only draws .13 amps when engaged. Shoot, my new signal switch and brake light switch will last forever this way.

Now where to place the relays; under the dash or in the trunk. I’m favoring the trunk as I loathe working under the dash.

Any other ideas out there?

 

[Mach1 Driver]

It's worse than you think. The turn filament on an 1157 drags 2.1A at 12.8v. But your alternator will probably be changing; mine charges at 14.4v giving 2.32A each. The relays will work but the on/off action will reduce their life, but at least they will last longer than the overworked switches. Put them somewhere where they are easy to change.

 

[Woodchuck]

Go with the LED's and install a "soft-start" driver on each side's circuit...

http://www.farnell.com/datasheets/72049.pdf

 

[Mach1 Driver]

Huh, that's a cool little chip. It's only 1 amp though. Considering that a 67 would have over 100 LEDs in the cluster, it would take considerable wrangling to get it all to work. And its probably only available in surface mount, which makes its a pain for the hobbyist- I still like DIPs. Anything I have to use a magnifying glass on and tweezers is too much work.

 

[gordonr]

Your idea is sound. The T/S switches would melt from excessive current issues and the contacts would sink. Many modern cars use relays for for turn signals and brake lights int he rear. Off hand I remember Fiero's running the relays in the back (but for 2 of the 3 light bulbs using the courtesy trunk light circuit for pin 30 on the relay for its perspective side) and Chryslers running the relays under the dash being activated by the BCM just as a couple of examples.

 

[2nd 66]

I started reading your post and couldn't wait to suggest using a relay but you solved your own question,I'd probably trunk mount it

 

[Woodchuck]

Huh, that's a cool little chip. It's only 1 amp though. Considering that a 67 would have over 100 LEDs in the cluster, it would take considerable wrangling to get it all to work. And its probably only available in surface mount, which makes its a pain for the hobbyist- I still like DIPs. Anything I have to use a magnifying glass on and tweezers is too much work.

1157LED's only pull .12A on the brake circuit each. That's only .36A total.

 

[Magnus]

I think the Cougars had the relays in the trunk, so Ford must have thought that was a good place for them.

 

[Mach1 Driver]

1157LED's only pull .12A on the brake circuit each. That's only .36A total.

I got my information from Bulb Town. It says one filament of a 1157 is 0.59A at 12.8v and the other is 2.1A at 12.8v. Don't ya just love the internet- there are lots of answers but perhaps none are correct.

 

[RV6]

I finally got the hot wire run from the front to the trunk. I had installed the relays and a new Shee-Mar turn signal switch a few days ago but was to lazy to pull interior pieces out to run the hot wire. I ran a fused hot wire to the trunk this morning. The new switch and relays work! I ran a fused 12 AWG hot wire for the lights. Boy howdy dogs are they bright.

 

[Paul1958]

1157LED's only pull .12A on the brake circuit each. That's only .36A total.

I got my information from Bulb Town. It says one filament of a 1157 is 0.59A at 12.8v and the other is 2.1A at 12.8v. Don't ya just love the internet- there are lots of answers but perhaps none are correct.

Mach1 Driver

You are BOTH correct. But I think you missed the fact that what Bartl (Woodchuck) was talking about is a 1157 LED bulb with draws much less current that a standard 1157 incandescent bulb that you are talking about.

Paul

 

[slhstang]

light problems of my own

I don't want to still your thread. I think I've got the same problem. All turn signals work, headlights work, but brake lights and tail lights have stopped working. I had just put in Scott Drake Sequential tail lights a couple of weeks ago in my 65. I'm thinking the Turn Signal switch and hoping it is not the brake light switch. Any thoughts

 

[Mach1 Driver]

Mach1 Driver

You are BOTH correct. But I think you missed the fact that what Bartl (Woodchuck) was talking about is a 1157 LED bulb with draws much less current that a standard 1157 incandescent bulb that you are talking about.

Paul

My apologies to Woodchuck- I did not see LED after 1157. I have seen 1157 LED bulbs advertised but have not seen the specs. I think Phillips makes the only DOT approved lights (their 12836B2). They have a 12yr guarantee and are instant-on so it reduces the stopping distance of the car behind you by 20 feet at 75mph

 

[RV6]

I don't want to still your thread. I think I've got the same problem. All turn signals work, headlights work, but brake lights and tail lights have stopped working. I had just put in Scott Drake Sequential tail lights a couple of weeks ago in my 65. I'm thinking the Turn Signal switch and hoping it is not the brake light switch. Any thoughts

Are these LED or incandecent?

The 65 is a little different than my 67 but if the turn signals work the brake lights should work. Make sure you have power to the brake light switch. My bet is the brake light switch. As for your tail if they be incandescent the problem could be two much amperage draw in the headlight switch and the switch is now toast. The system was designed to support 2 bulbs in the rear and 6 bulbs is taxing it beyond design limits. Relays seem to be in your future.

 

[pprince]

I must be missing something here.

If your turn signal switch continues to fail why don't you install an oem unit?

 

[Paul1958]

Are these LED or incandecent?

The 65 is a little different than my 67 but if the turn signals work the brake lights should work. Make sure you have power to the brake light switch. My bet is the brake light switch. As for your tail if they be incandescent the problem could be two much amperage draw in the headlight switch and the switch is now toast. The system was designed to support 2 bulbs in the rear and 6 bulbs is taxing it beyond design limits. Relays seem to be in your future.

The turn signals and brake lights share a common set of filaments in the bulbs so if the filaments are good both should work. However its important to recognize that the two circuits (turn signals, stop) do not share the same power source. The stop lamps are powered from the 15A CB in the headlight switch (which also powers the marker/tail lights, instrument panel illumination lamps, and the horns) and the TSs are powered from the 14A ASSY fuse. This is the same 65-68. So there are several scenarios in which the bulbs are good and the stop lamps work but not the TSs, or vice versa.

Hope this helps
Paul

 

[Mach1 Driver]

I believe that what you are getting at is that the turn signals and brake lights share a common set of filaments in the bulbs so if the filaments are good both should work. However its important to recognize that the two circuits (turn signals, stop) do not share the same power source. The stop lamps are powered from the 15A CB in the headlight switch and the TSs are powered from the 14A ASSY fuse. This is the same 65-68.

Hope this helps
Paul

Its the same in 69s, except the TSs are powered by a 20A fuse. If you care to see it in schematic form go to Stangfix.com, Electrical Board, and see "A REAL Schematic". Its the first real schematic for our cars- everything else has been a wire diagram. Wire diagrams tell you where to connect the wires, while a schematic shows you how it works. The KB restrictions on this site prohibit me from uploading it here. Its in pdf format and Exterior lighting is on page 3 of 4.
I'm an electrical engineer and I personally wouldn't attempt to figure out a circuit that complex without a schematic, so I converted the wire diagram into a schematic. Normally the engineer starts with a schematic and then makes a wire diagram- this just required reverse engineering.

 

[Paul1958]

A lot of folks use the terms 'wiring diagram' and 'schematic' interchangeably and in some respects they are. In the case of the Ford diagrams for the early cars they are basically both a mechanical representation of the harness(es) and electrical representation of the circuits. I kind of like them as they show exactly what the connectors look like, and where different things are physically located, etc. They can be a bit confusing sometimes in that it can be hard to tell where a wire is terminated in some instances. If you purchase the printed wiring digram books they include the Ford 'master diagram' which shows the entire vehicle wiring on one diagram - at least the 1968 book has this. Ive never seen this master diagram published online. The old diagram set do have their faults such as the lack of any diagram for 'power distribution' like you would find in more modern documentation. For my 68 I drew my own.

Good luck
Paul

 

[Mach1 Driver]

Wire diagrams have their place- they help you connect wires.
A real schematic rarely makes any attempt to identify wires or plugs or connectors. A real schematic tries to show the internal workings of a component when it helps to explain a circuit. A real schematic simplifies.
My reference material is a Ford authorized 1969 Helm Dealer Shop Manual with 16 11x17 drawings in wire diagram form. It simplified nicely into a schematic with only 4 letter size pages 8.5x11 (12.5% of the wire diagram size).