Turbocube

My Jeep has a very simple dash, with two huge dials, fuel on the left and speedometer on the right, and around them are four indicator lights (such as oil pressure and battery). But, although my Jeep is an AW4 automatic, I thought it might be neat to have a tachometer. I figure I might be able to use an LED number display.

My question is, does every XJ PCM detect the RPM, meaning there's a loose cable somewhere hanging around for me to use? If so I imagine that its a wire that applies increasing amounts of voltage that normally moves the little dial, and I could do some electronics work to make that LED display accurately read RPM.

Thanks in advance!

SoCalxJ4.0

I believe the connection is the ribbon cable. You could also get a new instrument panel from around your same model year.

Turbo X_J

What's wrong with the negative side of the coil?

jedijeb

I got a simple Sunpro Tach from Adavnce Auto for about $30. It isn't digital but it works and only requires a positive wire to a point that comes on with the key and a wire that connects to the negative side of the coil. You can probably find a digital one that works the same way.

Bustedback

Why not just swap the cluster with one that has a tach? Just change the oil and temp senders for ones that are for a gauge vs an idiot light. The wiring is already in the cluster plug. It's a very simple swap.

Turbocube

Ah, I suppose that would be best. So its really as simple as unscrewing the old cluster, attaching the existing wiring to the new cluster, and screwing that one in?

Bustedback

Plug and play. Just need to change the oil and temp senders on the engine.

Turbocube

Okay, so to be entirely honest I have no clue what a temp sender is. But why in the blazes would the oil need to be changed? Gah, I just changed it recently.

Lowrange2

The oil pressure sender...

Turbocube

D'oh. Must have missed that my first time around.

Not so sure I want to do all that (+ the cost of the new cluster) for a novelty tachometer on my automatic Jeep... I'd rather make my own, if possible.

Would you be willing to describe the best way to access this ribbon cable?

freegdr

You have to change the senors for temp and oil pressure to read correctly you changing from lights to gauges which is much better than idiot lights .The tach is a free extra no changes need to be made for it to work.

freegdr

And changing the two sensors that's it.

Jeepster242

What year? My 99 had the same basic cluster originally, but i replaced it with a complete cluster (speed, tach, fuel, volts, oil, temp) and no mods were required. I just pulled the old one out, and plugged in the new one in its place! Took less than an hour