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75 Posts
Discussion Starter #1
I am wanting to put a shift light in, does anybody know what I am going to need to make it work?

822 Posts
Why on earth would you want a shift light. On the cars that have one..I never use it. They all tell us to shift at 2000 rpm's which is a waste. I would recommend scraping that idea.

1,746 Posts
I think he means the shift lights that light up when you approach the engine red line. That way you can keep your eyes on the road instead of watching the tach to keep under the rev limiter.

1,574 Posts
The route I am going is having a MSD RPM activated switch(MSD-8950) converted to single cylinder operation. Then tapping into one of the coil packs and running that to a shift light.

75 Posts
Discussion Starter #5
That will work?? I found a tach interface module from Pauls High Performance but I think they are around $285 or so. Kind of steep figuring thats just to get a shift light to work...then you have to purchase the light or shifter light combo?

714 Posts
I was wanting to put a shift light on mine also and I ran into this write up on the Auto page. Looks like it might be a little more involved. Sorry for the length.

We are getting more and more requests for tach signal wires and
connection points on all kinds of new vehicles, and virtually every
new vehicle has at least a DIS (distributorless ignition systems, or
coil pack as it is more commonly referred to). The days of the "old
distributor and coil" are gone, friends. This is a whole new ball of
wax. The automotive industry appears to be shifting toward an
even newer ignition system - C.O.P. This stands for coil on plug
ignition system, which consists of attaching a coil atop each
cylinder's spark plug, eliminating any coil pack, distributor, or plug
wires. The computer for the vehicle controls the targeting for firing
the plug when needed, supplies the voltage to the coil to
discharge, and has a "monitor" to ensure that the coil did fire and
at the appropriate time.

Ok, now you're asking your self, "What does this mean to me?"
The answer: if you have a late model vehicle (most '99 and newer
models) with C.O.P. ignition, it has everything to do with you.

We have not had much, if any, success installing any of our engine
RPM devices (tach, shift light, RPM activating module, etc.) on this
type of ignition system. This is due to each cylinder seeing a
portion of the entire motor's firing order. First, say for instance you
have an 8 (eight)-cylinder motor, such as a Ford Mustang, for
example, and it is a '99 or newer model. You have eight cylinders,
and that means you have eight coils now, too. Trying to splice into
one of the eight coils seems like the first thing to do, but it IS NOT!
You see if you were to do that, you would only see 1/8 of the
engine's true RPM signal. This is far too spaced out or sporadic
for our tachs to register correctly off of. Also, we have seen on
some of these late models that there is multiple spark discharge
at lower engine RPM, which causes severe pointer bounce (which
makes the tach pointer swing wildly from 1k-3k) usually within the
0-2k RPM range. You say to yourself, "combine the signals". This
won't work either, because you would first to have to find two
opposing cylinders in the firing order, and then build an inline
adapter or circuit to prevent crossfire, or potentially damaging
cancellation of both cylinders firing. This situation could allow fuel
to load up in the cylinder tubes, then when it does fire, BOOM.

This leads us to the next point and question, "Why can't I just splice
into the wire(s) that goes to the tach in the cluster?" This sounds
like a viable option, but the signal to the cluster tach is not the
same signal as what our tach needs to see (12v square wave).
This is commonly referred to as Multiplexing, which is the process
of communicating several messages over the same signal path or
wiring. In most cases, the wire that has the tach signal also has the
signal for any of the following:

LOW FUEL level indicator
The standard gauges; oil, water, fuel level and volts
Brake warning light
Seat belt
And so on...

As you can see, for this example '99 Mustang there is a lot more
than just the tach's engine RPM signal going up to the cluster and
our tach cannot derive the signal needed to operate, nor is it the
correct signal. We have also found that the rate of refresh is very
low, so it does not give as accurate readings as our tach needs to

Now, this dark cloud looming is not all a lost cause. Some
vehicles, even to the day this article was written, had the new
C.O.P. ignition system and also a devoted "tach signal" from
which to work from. A few examples of such applications are:

1.Ford Triton V-10
2.GM LS1(used in the Camaro, Firebird, Corvette, Silverado)
3.'01 Honda Civics

As stated above, 1) the Ford Triton V-10 motor, which has what
they refer to as a CTO (clean tach output) which our products, after
some modification, are capable of working on. Also, 2) the new
LS1 motors found in such vehicle platforms as the Pontiac
Firebird, the Chevy Camaro, and the Chevy Corvette. And lastly,
3) '01 Honda Civics, one of the latest additions to this listing, but
they too have a tach wire to work off of. These vehicles have the
C.O.P. ignition, yet the factory cluster tach has a wire that uses a
signal our tachs can work off of from the computer that you can
splice into to obtain the engine RPM signal from.

So with all this in mind, we are trying to do everything we can to
stay compatible with the later model ignition systems, but don't
always have the answer. We STRONGLY urge you if you are
looking to purchase one of our products that you check the ignition
system first, to see what you have to work with, then step two
should be to call us and inquire about the compatibility with your
specific vehicle.

1,130 Posts
I had a link for install of a shift light in the 99+ Mustangs that didn't need all that extra $300 adapters. The link was at, but the site is down, and has been for some time. Drat!
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