94 K2500 - Swapped 6.5T Diesel to 5.3 LS - Making factory tachometer work! Easy!

[94Swap]

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.

You must be registered for see images attach

You must be registered for see images attach

 

[0xDEADBEEF]

Nice. What happens after 5k rpms? Does it keep going or peg the needle?

 

[94Swap]

Nice. What happens after 5k rpms? Does it keep going or peg the needle?

Im not sure, I dont know the history of this engine so Im not brave enough to send it to redline. However if it works like my old 92 with a 350, it pretty much just keeps going.

 

[fivefeezy]

Thank you! Exactly what I was looking for.

 

[Phew]

I seen this is an older thread, but how much of a pain was it deleting all the diesel crap to make your swap work ?

I'm in the process of cab swapping my 98 crewcab the new cab was a diesel truck.

 

[Glenn8Weiss]

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.

You must be registered for see images attach

You must be registered for see images attach

Thanks, I've been looking for a way to get my tach working.. did a 6.0 LS swap on my 93 C3500 6.5 turbo diesel..

 

[hdvolks]

Thank you so much for this PRICELESS Info! I am doing a LS swap in my 92 that was a diesel/nv4500. This is exactly what I need to know.

 

[Fdiesbach]

I know this is an old thread but I have a question. I have a 95 k2500 that was a 6.5 and now a LS. My issue is the person before I got the truck cut all the wiring harness out to start from scratch on the swap I guess. Well guess who got to finish the job after I bought the project. My issue is the can not locate it he tach signal wire on the truck. Been looking for schematics and just shows the white wire. It’s been cut out so where would I look? Thank you for all the previous valuable information.

 

[89RCLB]

Here's a link to the field service manuals that you can download for free. Should be able to find our answer within them...

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com