Hi all! I just figured out how to make the tachometer work on my 94 K2500, which used to have a 6.5 turbo diesel and now has a 5.3 LS. I bought the truck with 3 working gauge. Fuel, oil, and coolant. Its an nv4500 truck so a tach is nice.
I searched and searched to find the fix. I tried direct wiring from the pcm, I tried wiring in a resistor. Nothing worked. There's very little info on the ex-diesel side of the swap community.
The diesels in these trucks recieved their tach signal from the alternator. The white wire in my case. The LS alternator only had 2 wires going to it with this painless harness. I thought the white wire from the LS alternator would be a signal to the tach, it was not. It would send a tach signal but would only register RPM up to 1500. A bit of back probing found the sweet spot on pin 1 (if viewing the connector from the front). I had to remove a pin from an unused connector to install into the alternator connector. Wired the OEM harness white wire in and now I have a tach.
I know most of the swaps are done from gas to gas, but for those of use who used to have diesels, heres how to make the factory tach work with the LS alternator.
I searched and searched to find the fix. I tried direct wiring from the pcm, I tried wiring in a resistor. Nothing worked. There's very little info on the ex-diesel side of the swap community.
The diesels in these trucks recieved their tach signal from the alternator. The white wire in my case. The LS alternator only had 2 wires going to it with this painless harness. I thought the white wire from the LS alternator would be a signal to the tach, it was not. It would send a tach signal but would only register RPM up to 1500. A bit of back probing found the sweet spot on pin 1 (if viewing the connector from the front). I had to remove a pin from an unused connector to install into the alternator connector. Wired the OEM harness white wire in and now I have a tach.
I know most of the swaps are done from gas to gas, but for those of use who used to have diesels, heres how to make the factory tach work with the LS alternator.
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