using hood turn signal lights as shift lights ?

[moparx]

at one time, i saw a post somewhere about using the hood turn signal lights in the hood as shift lights, while still retaining their original function as turn signal indicators.
they were ran through a relay of some sorts, that had two normally closed contacts, allowing the hood signal lights to operate as they were designed to do, then something triggered the relay to close both contacts on both signal lights, making them both come on at once, as a shift [indicator] light.
i hope i have explained this correctly.
anyway, i have played around with a couple of different relay types, using [or trying to] an MSD shift light [the one with the interchangeable rpm chips] as the triggering source.
nothing i have tried, 12 volt source or ground source, has worked out.
what am i missing here ? do i need a different rpm trigger device ? a different type of relay ?
i have searched different places for this info, but have struck out..............[and my hair is falling out in clumps.......]
any help is greatly appreciated by this old dummy !

 

[pnora]

You will need 4 diodes. One in each turn signal feed wire and one in each of the msd shift light feeds to the signals.

 

[PurpleBeeper]

You will need 4 diodes. One in each turn signal feed wire and one in each of the msd shift light feeds to the signals.

Please explain

 

[pnora]

Please explain

You do not want feed back. Thats the purpose of the diodes. they allow feed but will not back feed.

 

[w.Hudson]

I did the same thing but with the parking brake warning light in my 67 GTX.

I used a MSD RPM activated switch.

It worked very well. The parking brake warning light was very bright

 

[moparx]

thanks for the response pnora.
what value of diodes do i need, and where is the best source to get them ?
as to the number of diodes, as i only have two hood lights [that's obvious, of course] i don't understand why i would need two for the MSD light, as it only has three wires, hot 12v [ignition run], ground, and coil - [the input feed ?].
i have verified the MSD light works as it should, by using a 3000rpm chip. it comes on when my stewart-warner tach is showing 3000rpm.
i also tried to run an extra wire from the feed

pin on the 1156 bulb socket [12v] used in the MSD light, but with the key on, this added wire shows voltage present, even though the MSD light is off after the initial "test blink" the MSD light shows [as it is designed to do] when the key is in the run position.
is this [proposed] setup ran through a relay ?
would it be possible for you to post a wiring diagram ?
i am no rookie when it comes to wiring, but for some reason, i am having fits with this ! [if only my hair will quit falling out !]
one other thing to mention, i have changed the hood signal bulbs and the MSD light bulb, to LED's. is this going to be a problem ?
the hood signal lights work perfectly with the LED's i have also installed in the parking and tail lights, [along with the proper electronic flasher] and the LED [size 1156] in the MSD light works great, and is at LEAST 3 times brighter than the original [standard] 1156 bulb.
thanks again to all that can, or are willing to, help me out with this project.
​

 

[pnora]

Your light is using negative switching. So you have to configure a relay to activate off the negative switching. Doing that will allow the relay to supply a positive signal. You have to use a diode in each shift feed along with cutting the turn signal feed at each bulb and installing a diode in each feed. without all the diodes you will have back feeds and lights working when they should not be. If you do not want the turn signal function to work and just use the lights for shift lights no diodes are needed.

 

[INTMD8]

I used this relay-

Amazon.com

Right and left hood light wires go to 4 and 9


Right and left hood light wires from car go to 3 and 10.

5 and 8 are joined/connected to 12v

1 and 12 is relay trigger so one from whatever your RPM based output is and the other to power or ground (depending on if your trigger is power or ground of course)

 

[chargervert]

Very cool idea. The Charger hood signal lights work great for shift lights, and it would be even cooler on a 70 Road Runner or GTX where the lights are up closer to the windshield.

 

[not so famous bob]

I used this relay-

Amazon.com

Right and left hood light wires go to 4 and 9


Right and left hood light wires from car go to 3 and 10.

5 and 8 are joined/connected to 12v

1 and 12 is relay trigger so one from whatever your RPM based output is and the other to power or ground (depending on if your trigger is power or ground of course)

View attachment 1729551

first I`ve ever heard of this , its kick *** !

 

[moparx]

i tried that relay, and couldn't get it to work, using an MSD shift light. [the one that uses the plug in rpm chips]
i know i'm missing something here, but i can't figure out just what.
possibly, i need a different trigger source ? if so, what do i use that is adjustable for rpm points ?