My truck didn’t come with a tachometer and LS tachs are hard to come by. I used this poster’s suggestion on Isuzupup.com and purchased a Hall Effect aftermarket tach from Amazon for $18.99.
When it came, I wasn’t sure if the magnet that attaches to the main crank pulley could only go one way so I wired it up and passed the magnet over the sensor. Sure enough, it only works one way and I marked it with a sharpie to mount it correctly.
Wired up
No signal
Signal!
After scrubbing the main crank with a small stainless steel brush and some brake cleaner and rag, I epoxied the magnet and let it set for about a day.
Epoxied magnet and sensor mounting bracket
Then I used an aluminum L channel to make the sensor bracket by cutting out a V-notch on one side and bending it into a 90 degree angle. I was worried that it might not hold under the vibration from the engine and epoxied the cut out piece of the channel into the corner.
This got mounted with a water pump bolt and the sensor hole was drilled out to be in line with the magnet.
I pulled power from the cigarette lighter with a tap:
The dash already had a hole from the aftermarket heater control. I trimmed the hole a little larger for the plug in the back of the display to fit through.
The display is meant to be inserted into a cutout hole, but I wanted to use 3M mounting tape instead in case this wasn’t permanent. I found that a small 1/4″ piece of plywood filled the back of the circuit board so the tape had something to mount to. I hot glued it on, cleaned the dash with some rubbing alcohol, and attached it with the tape.
Plywood attached with a healthy amount of hot glue
Plywood just barely is above the surface
Mounted in place
Overall, this was cheap and took about four hours of work. The display fluctuates a few RPMs (+/- 4) and I’d guess that if the sensor were analog it wouldn’t be noticeable.
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