Electrical Experts: I've got a question:

I built an adapter for a 3-wire turn signal switch per ******jack's instructions (see schematic below) and have it working...sort of...:

The signals work as they should when you aren't pressing the brake pedal, but when you press the brake pedal you get brake lights but no more turn signal @ the rear. Let off the brake pedal and the signal comes back on. Kinda the opposite of how it is supposed to work.

So what obvious mistake did I make? I know it's going to turn out to be something silly.

 

Your brake light switch is byp***ing the flasher somehow when the brakes are applied, allowing power to both rear circuits. You may have it wired to the 1-2 1-2 bus........

 

The lights go to ground so i,d think the switch should be pos, not ground.The switch closes power to one side.

 

Not sure what I'm looking at in the schematic above. The two blocks in the middle are those relays? Basically what needs to happen is that the brake light power needs to be removed from the side of the circuit the turnsignal is powering (thus the relay I was asking about). Your best bet is to get a test light and test the setup with brake lights and without to determine where the power is coming from for the brake lights.

 

The wire from the brake light switch needs to either go to 1 and 1 or 2 and 2, not 1 and 2 as pictured. It is de-energizing one, and energizing the other as pictured.

 

Does the brake lights work with the turn signal switch in the middle (off position)? My guess they don't! Seems like the relay contacts do not agree with the schematic.

Pins 5 and 6 should be the C or common
Pins 3 and 4 should be the N.O. or normally open
Pins 1 and 2 should be the N.C. or normally closed

Check the relay pinouts first.

 

George: What u say is true with a conventional turn signal switch, but in this case two relays are used to take the place of the turn signal switch contacts, and the turn signal switch shown is merely completing the relay coil circuit by the grounded switch. Pins 7 and 8 are the relay coil pins.

 

It could be the simple mistake alot of people make installing the bulb backwards or installing a single filament bulb in a dual purposed light socket

 

Here is a link to the original post (probably should have included this at the beginning...)
http://www.jalopyjournal.com/forum/showthread.php?t=566803 which clearly shows what relays are being used and which pin is supposed to do what.

The bulbs are all in and wired up fine, as is the brake switch. The whole thing was working fine with a more modern switch I had in the car till now, I just wanted to use an older style T/S switch.

Thanks for everyone's help. I really appreciate it. Please just keep it on the level of "Unsolder this from pin #1 and solder it on to #2" if possible. That is my sophistication level for this.

To d2 Willys: Brake lights work normally with the T/S switch in the center/off position. They just don't play well with the turn lights.

 

To d2 willys I think you are right with the pins.I have one of those old switches and was wondering how to use it.
I can make it work now on paper.
Left relay
Brake to 2
3 to L light
4to R Rear
5and6 common from signal flasher
Right Relay
Brake light to 2
3 to R front
4toR Rear
5and 6 common from flasher

 

Here is what I think your issue is:

The (old) new switch you are using to energize the relays has high contact resistance and barely allows the relay coils to energize when in the turn positions. When you hit the brakes, the relay that is suppose to be energized is dropping out due to the switch resistance. It may also be the ground wire on the switch is not grounded real well.

A quick way to isolate the problem is to just ground (with a jumper wire) the left or right turn wire from the present switch to a good ground. This will narrow it down to the switch.

(You could also check with a test light as follows: put switch in L and with the test light connected to a ground, put the test light probe on pin 7 of left relay (with switch in L position). If it lights (even dimly) with the brake switch actuated then the turn switch is doing exactly what I mentioned above)

One other question: Are you trying to do this on a 6 volt vehicle? If so you will need 6 volt relays.

Let me know if this is the issue!

 

Nope, s/b:

Left relay
Brake switch to 2
5 to L front
6 to L Rear
3 and 4 common from signal flasher
Right Relay
Brake switch to 1
6 to R front
5 to R Rear
3 and 4 common from flasher

Note: The reasoning behind this weird pinout of the two relays is likely because the original design is using a printed circuit board, and the board traces route easier using this pinout.

 

Check the bulbs. Even if they're new.

I had an old '47 Chevy when I was starting out... When I was wiring up some simple wiring, I had an electrical gremlin...
When I got to the taillights, they were always on bright. When I hit the brakes, they were bright. When I turned on the running lights, they were bright. When any electricity went back there, they were bright.
Hmmm...
I had them wired right... New wires. New bulbs. New pigtails. New brake switch. Everything was new. I had the guys in my club look at the wiring... It was fine. . But it wasn't working right...
I went back through everything. I spent hours.
I finally took it to an automotive electrical place to have them look at my work. They said it should be working fine, but couldn't figure out why it wasn't.
Depressed, I was talking with dad... I told him how much time I had spent, how much money I spent, and how many people had looked at it. But the bulbs just wouldn't work right...
He said "did you check the bulbs?"
They're brand new bulbs!
"So?"
So out I go to look at the bulbs. They looked fine. But I pulled a bulb anyway and stuck in another new bulb I had laying around.
They worked fine.
It turns out one of the new bulbs I had put in apparently had a short inside the housing.

For the turn signal circuit, try this one I drew up for simple turn signals. It works for me.

http://www.how-to-build-hotrods.com/turn-signals.html

 

great idea using the trailer converter! Now why didn't I think of that considering my job involves those things?

 

Had lots of trouble with the trailer converters failing, used them when mounting U.S. bodies on Asian truck ch***is. Ended up using similar circuit; but with four common 5 pin Bosch type relays. No problems with them after that, except when drivers mess with wires like they do. Maybe converters are better quality now.

 

I found this post interesting because i have and old signal switch and i was wondering how they made it work.post 9 shows relay from Radio Shack and that one will work.
The posted diagram is not the same, and will not work.
This means the bulb needs to do double duty and act as a brake light and a turn light! But the turn signal switch has only 4 wires; one for the internal turn signal light and 3 wires for its turn function (a common wire that either shorts one or the other of the remaining 2 wires).

You will need to be able to solder and you will need these parts from Radio Shack. While you're there you can grab a soldering iron if need be.

Quan***y 2 - 12VDC/10A DPDT Plug-in Relay Model: 275-218 Catalog #: 275-218
This should work now
Left relay
Brake to 2
3 to L light
4to L Rear
5and6 common from signal flasher
Right Relay
Brake light to 2
3 to R front
4toR Rear
5and 6 common from flasher
All info is from post 9

 

Post 9 ? Where exactly is that, on this thread? Or some other place. All I know is the relays are typical 2C footprint and what the drawing shows is correct, his switch has resistance issues!

These relays are from the original thread and look like Tyco 2C relays:




Radio Shack just packages the damn things.

Think carefully about your pinouts:

5 and 6 are the common wipers of the relays. And the stop/turn lights are where the common wiper goes, right????? You either switch the stop/turn lights to the flasher or to the brake switch....

AND THE ORIGINATOR OF THIS THREAD SAID HE HAD (ORIGINALLY) ANOTHER SWITCH HOOKED TO THE CIRCUIT AND IT WORKED. SO IF YOU SWAP ONE SWITCH THAT WORKED WITH ANOTHER THAT WORKS A LITTLE, THEN THE SWITCH IS LIKELY THE CULPRIT.

 

I'm swamped at work lately, but will report back as soon as I get a chance to work on the car.

I appreciate your thoughts on my problem.

 

Quote: "AND THE ORIGINATOR OF THIS THREAD SAID HE HAD (ORIGINALLY) ANOTHER SWITCH HOOKED TO THE CIRCUIT AND IT WORKED. SO IF YOU SWAP ONE SWITCH THAT WORKED WITH ANOTHER THAT WORKS A LITTLE, THEN THE SWITCH IS LIKELY THE CULPRIT. "

Just to clarify: I've not had a switch running through the 2-relay gizmo working before, I had a 7-wire switch which has the brake/turn switching internal to it, so I know the wires/bulbs/sockets work as-is, it is the 3-wire switch and the relay gizmo that are new to the system.

That said-
I just tried the suggestion above and byp***ed the switch entirely and grounded directly and had no change: I had brake lights but the brake lights killed the turn signal, so the problem seems to be the relay setup.

I'll see if George's suggestion above works next.

Any other suggestions?
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Okay-
I followed George/Maine's suggestion above, but that didn't solve my problem- it just changed it: Now The signals (still) work, but I have no brake lights at all . It did bring up a couple of questions re: George's plan though:

1. Are the #1 pins on both relays really supposed to be blank- as in not connected to anything?

2. Under the George plan what is supposed to be done with the #7 & #8 pins on each relay? At the moment I have the #8 pin on the right relay going to the "right-turn" side of the turn signal switch, and the #7 pin on the left relay going to the "left-turn" side of the turn signal switch. Then the #8 pin on the left and the #7 pin on the right are connected to constant 12volt power. This was how I had them before, and George's plan didn't say to change it, so I didn't, but is it right?

As usual I appreciate all advice.

 

I may have changed some wiring but you can check why i did and should work.
Relay left 4 goes to left rear, fasher is power to 5 and6 across.
Left position is 7and right is 8 and right relay is 4 to right rear.
When left relay is picked 2 drop out brake light for left turn.
When right turn is picked thur 8 no 2 drops right brake light.
When in middle both relay are at rest making a circuit for brake to boths 2s thur both 4s to rear lights.
So 2 and 4 are swicthes to get rear brakes lights,in middle of turn signal.If you have a 3 wire the middle will be ground and tie in to flasher ground.
Give it the smoke test good luck
George

 

What u did with the George plan has the proper result. Only the turn signals will work. The original plan is correct, but obviously there is something amiss.

Think of the relay logic like this:

Pins 5 and 6 are the wipers or to put it more clearly, the terminals that will take either the brake switch input or the flasher input. These are obviously the terminals that will go to the rear lamps. Pins 1 and 2 are the normally closed terminals and with no coil voltage the rear lamps will be connected to the brake switch. Lastly pins 3 and 4 are the normally open terminals that will only be connected when the coil is actuated. Now let's say the right relay is selected. The flasher output is routed to both front and rear right hand lamps. Since the left relay is not energized, the brake switch feeds the left rear lamp. Also it cannot feed the left front because of the empty terminal(s).

So this is how it is suppose to work, now why doesn't it work? You grounded the terminal coming from the switch and it does the same thing.

Ok, do your relays have the same pinouts as the ones I attached in one of my previous posts? Those are what would work with the original schematic. I would verify this first. You may have used a different set of relays, I have looked at the Radio shack site and found no pinouts on the spec sheet for their relays.

I will do some more research and come up with a solution.

 

I gave this some thought and need some questions answered:

1) Are u sure that the rear lamps are properly grounded. If they are not properly grounded it is possible for lamp that is suppose to be flashing gets voltage from the other side, which is suppose to be brake signal. Check these grounds first.

2) What does the front signals do when the brake switch is activated?

3) What happens with the tail and park lights on?

Try this test:

Pull the left rear bulb. Next select right turn and verify the right turn bulbs are flashing. Next depress the brake and observe the right turn signal bulbs for proper operation. If things work right, then there is some sort of grounding issues going on. ( You can also do this test for the left turn bulbs by removing the right turn and selecting left turn at the switch.

Look forward to your answers to these questions.

 

The Radio Shack relay is like 2 relays 135 and 246 , 7and 8 are coil. points 1 and 3 never touch and 2 and 4 never touch.
5and6 with touch 1 and 3 and 2and4.
You may want to jump from brake to light ,and make sure the brake switch is working.then go between 2 and 4

 

After looking at your orginal diagram.
I think if you just switch left relay 3and 5, 4and6,
right relay 3and5 and 4and6.
L flasher to feed 5and 6 across NOT 3and 4 3and 4

 

OK-
Thanks for the suggestions. I'm back to work after a day off so I may not get a chance to do anything right away, but I will report back when I do.

George-
Can you re-phrase your last post: I'm not sure what you are telling me to try.

 

This is on the money check the relays you are useing, the Radio Shack ones I used are not standard.
Most double pole relays have there wipers on 3 and 4, these relays have the wipers on 5 - 6

THE LAMPS GO TO THE RELAY WIPERS

THE BRAKE SWITCH GOES TO THE 2 REAR LAMP NORMALLY CLOSED CONTACTS

AND THE FLASHER GOES TO ALL 4 NORMALLY OPEN CONTACTS

 

To Fix your diagram.
Left Relay
Left Front to pin 3,
Left Rear to pin 2,
Wires from Flasher L put all to 5-6-5-6 across
Right Relay
Right Front to pin 2
Right Rear to pin 3
Leave all others the same even 1and 2

 

Ok now you have me worried, after checking again it is correct as draw

Oh I am so sorry guys I just checked it again the schematic is drawn as viewed from the pins and if wired as shown is correct but i think i fu*cked up and numbered them wrong on the schematic the 1 is switched with the 5 and the 2 is switched with the 6

 

Reference Post #17 relays shown. I took this picture right off your original thread, so I think they should be right. If you look at the picture, pins 5 and 6 are adjacent to pins 7 and 8. This location agrees with your schematic, the only issues might be 5 and 6 reversed, 1 and 2 reversed, 3 and 4 don't care. But if you think about it, it doesn't make any difference.

Now if you moved 5 to1 and vice versa, 6 to 2 and vice versa, the brake lights would still work, but the turn signals would not.

Relay configuration #2
Pins 1 and 2 are wipers, 3 and 4 NO, 5 and 6 NC

Now lets say that 1 and 2 are the wipers (lamps), 5 and 6 are NC (brake sw), and 3 and 4 are NO (flasher). Now it will work.

But let's say that 1 and 2 are the wipers (brake sw), 5 and 6 are NC (lamps), and 3 and 4 are NO (flasher). Now it will only work the brake lights, no turn signals.

4 woody says that both turn signals work correctly till the brake switch is activated. Sounds to me like the coils are dropping out when the brake switch is actuated, ie: voltage is reduced, possibly by the gauge of wire from the 12V source to the coils.

Just thought of something!! Is it possible that Radio Shack mispackaged 24V relays in a 12 V bag??? Nah, never! Or could 4 woody bought two 24v relays instead of 12V? My guess is that you could get a 24V relay to kick in on 12v, but if the voltage drops any further it might drop out.