LS Swap 69 Camaro tach question

[oakhill510]

Hey,

I had wired my factory tach signal wire to my LS harness tach lead. My factory tach is grounded and works. Only thing is, the respond on the tach is slow. Any opinion?

I had tried giving the tach more juice by wiring a 1k resistor from a Key on 12v source to the tach signal but its still the same respond. Maybe the 1k resistor was a bad one.

[Z06vet]

I have always had to use a tach adapter to make a factory style tach work when doing an LS swap. I am not saying it's the only way, but it has worked for me.

https://www.amazon.com/Auto-Meter-9117-Tachometer-Adapter/dp/B00063068W/ref=asc_df_B00063068W/?tag=hyprod-20&linkCode=df0&hvadid=312064613195&hvpos=1o1&hvnetw=g&hvrand=8158913388682759786&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9011660&hvtargid=aud-829758849484:pla-496661213412&psc=1

[oakhill510]

That a good price for that unit. Thanks. If all other fail, I have no problem getting this.

[icemanrd19]

Did you switch the gauge to 4 cylinder mode? The resistor connects to a 12v source inline to the the tach signal. Only issue i have is that it bounces some at idle.

[69_Sportsroof]

Hey,

I had wired my factory tach signal wire to my LS harness tach lead. My factory tach is grounded and works. Only thing is, the respond on the tach is slow. Any opinion?

I had tried giving the tach more juice by wiring a 1k resistor from a Key on 12v source to the tach signal but its still the same respond. Maybe the 1k resistor was a bad one.What inspired the resistor mod? Was it something you read somewhere? I haven't heard of it but I haven't researched LS swaps either.

Putting a 1k resistor inline with a 12V source means you would only get a Max of 12mA current to drive the tach motor. Giving it less resistance will increase the drive strength but I don't know if there's a current rating that you have to stay under to avoid burning the tach up.

[CarlC]

The tach in my Camaro, updated with a modern VDO movement, at first worked well with the LS swap then started acting erratically. The problem was a low signal voltage.

The cure is a 5k resistor with one end to the tach wire and the other to IGN+.

[oakhill510]

icemanrd19 (https://www.pro-touring.com/members/26778-icemanrd19) I am using a factory 69 Camaro tach. Theres no cylinder mode option.


69_Sportsroof (https://www.pro-touring.com/members/47207-69_Sportsroof) as for the resistor mod, I believe from what I read that, LS pcm doesn send low power to the LS tach wire and 69 Camaro (and older tachs) uses/need more power juice than the LS/modern tachs. So the 1k resistor mod boost the power on the LS send tach wire.
One souce : https://www.youtube.com/watch?v=FS7aRfYkFAQ&t=365s




CarlC (https://www.pro-touring.com/members/84-CarlC)
fixed your low signal voltage with a 5K resistor huh.....? I need to try that. Thanks.



Sorry about the late replies, I dont get notifications. (https://www.pro-touring.com/members/84-CarlC)

[oakhill510]

Heres the video of the tach working on youtube.



https://www.youtube.com/watch?v=gnGNGaSAIVU

[Motobrewmaster]

Here is some more info that might help you.

Cheers, Steve

https://forum.hptuners.com/showthread.php?36611-GEN-IV-E38-Tach-Settings-for-aftermarket-tach-(autometer)&highlight=autometer+tach