Need a little wiring help - LED for TC lock-up switch

[BigPapa]

I put a TC lock-up switch on my truck and since my APPS is bad causing lock/unlock issues I have the Org/Blk wire cut so that it only locks up with the switch. The switch works flawlessy but I wanted to put an LED in line so I could tell when the TC is locked. Here is a very elementary diagram:



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The LED does not come on when the TC locks up and it will only flash for a split second when I unlock the TC. The switch I'm using is a floor mounted dimmer switch for a late '70's Ford truck. As I noted, the switch works perfectly.



What's up?

 

[GW208]

Try reversing the wires on the LED, you might have the polarity backwards.

 

[Bill Stockard]

I had an indicator light on my previously owned '97 3500 with an add-on torque converter lock up switch. I used a double pole switch from Radio Shack with the control of the lockup on one side and fused 12-volts to the indicator light on the other side. It wasn't a LED indicator, but it would work in the same fashion.

Bill

 

[BigPapa]

Thanks for the replies.



Polarity is correct. It does come on, just flashes for a second.



I don't want to give up my floor switch.

 

[mwilson]

Scott,



I have not installed one of these T/C switches in a while so am a little fuzzy on details, however as I remember you are grounding the Orange/Black wire to lock it,right??



If so, I would use a relay with the floor switch as the trigger. You will have to power the relay and have it send power to the LED when the ground is made.



Does that make sense??? I think it would be the easiest way to get what you want.



Edit... As you are using a dimmer switch already wire the relay to activate with ground removed, that way you could hook to the currently unused third terminal of the floor switch. ???



Just a thought.



Mike.

 

[Partyat33]

Well, you might consider the voltages available. If the LED works on 12 v, and the TC solenoid uses 12 v, they can't both have 12v. You only have 12v to give. Try putting your solenoid after the switch in parallell with the solenoid.


Dennis

 

[BigPapa]

Thanks for the idea Mike.



Anything is possible, so, let's say the LED was assembled wrong with the poles reversed. Would it act like I described?



Just for review, as I tried to illustrate above, grounding the Org/Blk wire from the PCM locks the TC. I have a wire grounded that goes to one side of the dimmer switch. A wire from the dimmer switch to the Org/Blk wire at the PCM. The TC locks and unlocks as it should, so the ground is working properly. I wired the LED in with 12V to the RED (Positive) wire coming out of it and the BLACK (Negative) wire coming out that connects to the wire between the switch and the Org/Blk wire.



The LED should illuminate when the TC is locked but all it will do is flash for a split second when UNLOCKING the TC. It does nothing when locking it, when it is locked, or when it is unlocked.

 

[BigPapa]

Well, you might consider the voltages available. If the LED works on 12 v, and the TC solenoid uses 12 v, they can't both have 12v. You only have 12v to give. Try putting your solenoid after the switch in parallell with the solenoid.

Sorry, you lost me here. I'm dealing with grounds. The only 12V I'm using is the 12V to supply power to the LED when I ground it.



I've done this same thing with a switch that controls the A/C compressor. It's the same "ground it to run" scenario. It works properly with the LED illuminating when the compressor is on.

 

[mwilson]

Thanks for the idea Mike.



Anything is possible, so, let's say the LED was assembled wrong with the poles reversed. Would it act like I described?



Just for review, as I tried to illustrate above, grounding the Org/Blk wire from the PCM locks the TC. I have a wire grounded that goes to one side of the dimmer switch. A wire from the dimmer switch to the Org/Blk wire at the PCM. The TC locks and unlocks as it should, so the ground is working properly. I wired the LED in with 12V to the RED (Positive) wire coming out of it and the BLACK (Negative) wire coming out that connects to the wire between the switch and the Org/Blk wire.



The LED should illuminate when the TC is locked but all it will do is flash for a split second when UNLOCKING the TC. It does nothing when locking it, when it is locked, or when it is unlocked.

I think the Org/Blk wire is a signal wire ie; very low amount of voltage or simply one of many ground legs for the BCM, TCM or whatever it is. I think you need to pull your LED out of the mix, I just don't think it will work where you have it. Then supply the LED with a clean 12 volts using the relay. Then the ground provided by the time tested dimmer switch can take care of both needs.



You could verify this by testing the Org/Blk wire for voltage and also try hooking the black wire of the LED to ground rather than in series as you have it now.



It is interesting that this works on the switch for your air compressor. Still thinking that through.



Mike.

 

[Bill Stockard]

I think the Org/Blk wire is a signal wire ie; very low amount of voltage or simply one of many ground legs for the BCM, TCM or whatever it is. I think you need to pull your LED out of the mix, I just don't think it will work where you have it. Then supply the LED with a clean 12 volts using the relay. Then the ground provided by the time tested dimmer switch can take care of both needs.



You could verify this by testing the Org/Blk wire for voltage and also try hooking the black wire of the LED to ground rather than in series as you have it now.

Mike.

Yep, that's why I used a double pole single throw switch. The voltage off the torque converter lockup solenoid signal wire is only about 5-volts and will not illuminate a 12-volt bulb/LED.



Bill

 

[BigPapa]

I think the Org/Blk wire is a signal wire ie; very low amount of voltage or simply one of many ground legs for the BCM, TCM or whatever it is.

Mike.

I'm not dealing with voltage, just a ground. The wire I have the negative side of the LED tapped into is literally 1' from the switch and the ground is 3" from the switch.

Yep, that's why I used a double pole single throw switch. The voltage off the torque converter lockup solenoid signal wire is only about 5-volts and will not illuminate a 12-volt bulb/LED.



Bill

The supply voltage to the positive side of the LED is 12V. It's tapped into the same 12V that the LED for the A/C switch is on. The TC LED is wired exactly like the A/C LED and I used the same switched 12V source for both LED's. The A/C LED works perfectly whether the TC is locked or not. This leads me to believe that both LED's should be wired correctly. The A/C compressor and the TC both work properly indicating that both ground wires are grounded properly. The only thing I can think of is that the LED for the TC is wired backwards or defective.



Please don't take my replies as argumentative. I'm an idiot when it comes to wiring. I'm just trying to understand and explain my idiotic logic to you so you can understand my thinking.



Thanks for the replies.

 

[mwilson]

I'm not dealing with voltage, just a ground. The wire I have the negative side of the LED tapped into is literally 1' from the switch and the ground is 3" from the switch.







The supply voltage to the positive side of the LED is 12V. It's tapped into the same 12V that the LED for the A/C switch is on. The TC LED is wired exactly like the A/C LED and I used the same switched 12V source for both LED's. The A/C LED works perfectly whether the TC is locked or not. This leads me to believe that both LED's should be wired correctly. The A/C compressor and the TC both work properly indicating that both ground wires are grounded properly. The only thing I can think of is that the LED for the TC is wired backwards or defective.



Please don't take my replies as argumentative. I'm an idiot when it comes to wiring. I'm just trying to understand and explain my idiotic logic to you so you can understand my thinking.



Thanks for the replies.

Sorry Scott, I missed the 12v that you indicated on the schematic above... ..... trying to do too many things at once... .



So after rethinking this during lunch try grounding the LED to something else as a test to see if it is defective. If the LED works during that test then I would suspect the Org/Blk wire responds to a pulse, not a steady ground perhaps???



Maybe JLandry or Cerb will spot this and straighten us out. I have hooked up a few T/C lock switches but never tried to do it with a separate indicator light. Always used one that was built into the switch.



Have just sent them both an e-mail with a plea for help... .



Mike.

 

[BigPapa]

try grounding the LED to something else as a test to see if it is defective. If the LED works during that test then I would suspect the Org/Blk wire responds to a pulse, not a steady ground perhaps???

Good idea there. See, why couldn't I think of that?



I'll try it and get back.

 

[cerberusiam]

Move the LED between the switch and ground, add a 33 ohm 1 watt resistor between the ground and LED also.

Since you are over riding the factory setup you only want the LED to light only when the swithc is activated. The lockup swithc sense wire is a ground wire. It has to be grounded so the solenoid will activate. Should have 12 volts but not much load on it.

 

[BigPapa]

Move the LED between the switch and ground, add a 33 ohm 1 watt resistor between the ground and LED also.

If I do this, then the LED will be grounded at all times, correct?



I took Mike's suggestion, disconnected the ground wire from the LED and connected it directly to ground. No illumination. Checked between the ground wire and ground and had 12V, for a minute. Now I have nothing. Double checked where I had it grounded with another 12V source and the ground is good. Tells me I have a bad LED.



Man, I don't want to tear that pillard pod apart AGAIN... ... .

 

[cerberusiam]

If I do this, then the LED will be grounded at all times, correct?

Yes, but you need to remove the 12 volt supply to it and wire it inline with the switch to ground circuit. Whne you close the switch you complete the ground circuit to activate the lockup. The LED will light when current flows thru it.

 

[BigPapa]

Well, I wired it your way cerb and I've got some WEIRD stuff going on.



I tapped the positive side of the LED into the wire between the switch and the Org/Blk wire. I tapped the negative side into the wire between the switch and the ground. At first it just flashed when unlocking just like I mentioned in the OP. Then, I unlocked the TC while slowing down coming into a 40mph speed limit and the LED came on and stayed on all the way through town until I locked it again. It stayed on @ 2 miles. After I locked it I drove @ 7 miles and unlocked it again coming to a stop. It flashed again when unlocked and went out, BUT, when I came to the next stop the LED tried to come on several times. I was not switching it at all at this time. Now I'm SO CONFUSED!



I had it working properly before I changed the wiring to cerb's way for a bit after I got a new LED and ran new wire from the 12V source and the ground. I thought I had it narrowed down to the floor switch but then it started doing it again. That's when I wired it cerb's way and headed home.

 

[cerberusiam]

I think you burned the LED lamp out with the load. What is the amperage rating on that LED? Most LEDS have a milli amp rating so even 1 amp thru them will cook them and they just kinda flash occasionally and die. The lockup solenoid is powered by a 30 amp circuit which the solenoid pulls most of the load out but I think there is still enough to kill an LED.



If you want a light to indicate when the switch has been engaged then it needs to be inline with the circuit. The way you wired it around the switch grounded the lockup circuit all the time and burned the led out, plus, it is giving enough resistance the TC did not lock. If it was capable of handling anymore load it would have come on nice and bright, the TC would have locked and stayed locked.



Thats why I suggested the LED inline between the switch and ground. That way, it only lights when the switch has been activated. Hopefully the solenoid and switch would pull the load and the LED would not give much resistance for the ground circuit the solenoid needs.



The way you had it originally worked because the only time a gorund circuit was made was when the swithc was activated. Electricity could flow from your switched source thru the switch to ground at the same time the solenoid grounded. However, that circuit also needs ot milliamp or it will just burn the LED out after a while. The other problem with that setup is if you EVER ground that circuit back the the org\blk wire, in the solenoid or VB harness, or the power wires that feeds it you will see smoke and burned wires before it pops the trans relay. That would be bad juju.



If you have to wire circuits that have mor ethan one power source together you need a one way gate on them so power cannot backfeed the other circuit. You also really need a ressitor between the switch and ground to protect the system. Right now, with the switch on if you ever ground that circuit back to the trans relay you will be replacing harnesses and componenets. It will draw enough current to nelt a wire right out the harnes but not pop the relay. With a resistor in that circuit it will pop a lot sooner. Usually a 1 watt 33 ohm resistor will protect it and not blow easily.

 

[PBJ2500CTD]

BigPapa,

Are you using a special 12v LED or a standard LED? Most LEDs require a resistor in series to protect it from excess current which will take all the "magic light" out of it in short order. If you know he LED specifications you can use the following website's calculator to determine the resistor size needed. If you have the LED number you can Google it to get the "white sheet" which contains the operating specifications.
http://www.kpsec.freeuk.com/components/led.htm
http://www.ohmslawcalculator.com/led_resistor_calculator.php

 

[BigPapa]

Here's the specs on the LED:



Specs:



Emitted color: Orange

Intensity MCD (typical. ): 110

Wave length nm (typical): 585-590 - 590 max

Type (size): 4mm

Lens color: Orange

Viewing angle (degree): 80° typical

12V/20mA 25max 15mA



You can see it here: http://www.radioshack.com/product/index.jsp?productId=2062570



OK cerb, so I misunderstood where to wire the LED. You're saying I need to do it like this:



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instead of like this:



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Which is the way it is now.



I'll disconnect the LED before driving tomorrow. The TC still locks and unlocks as it should and has during all of this. When I ground it, it locks. When I break the ground, it unlocks. The LED still lights up, just not when I'd like it to so I don't think it's burned out.



Thanks for all the help fellas.