Tach
 

I have a '97 Ram 3500 with the Cummins. The tach quit working,is ity controlled by the crank position sensor? Thanks

Yes it is.

What is the "gap" needed between the sensor and harmonic. Also, what is the "relationship" with the alternator?

Thanks

im dealing with the same issues. i jumped my truck and lost tach, speedo odometer, overdrive and tc lockup. I've changed the crank sensor with no change so im thinking next step is check the pcm. the gap for the crank sensor should be .049-.051 i used a business card, it was a perfect match for my feeler gauge and was much easier to work with. that crank sensor basically tells the pcm the engine is running but due to the magic of mechanical diesel the engine doesn't need the computer to run:jump::jump: however the alternator is tied into the pcm to basically turn it on and off. so no signal that the engine is running means no charge from your alternator. crank sensor is an easy fix and since yours is a 96 be sure which crank sensor you have. they changed at some point between 95 and 96 and your parts store may not know that. i have a 96 2500 12 valve with the 95 crank sensor. took me days and lots of heartache to figure that out. :argh::argh::argh: hope i helped. im just shooting out everything I've found on my electrical hunt. my most recent discovery is that my obd2 port has no reading coming from it.

Thanks!! I finally resolved the problem. The feeler gauge (steel) was the culpret. We finally read deeper and and found a blurb stating that a brass feeler was needed which makes semse as the sensor is essentially a magneto brass is not magnetically conductive. Anyway, it all seems to be working at the moment...........tach, alternator and shifting. I hope it stays that way. Thank you for sharing you were spot on!!