Need more Tach Juice

[Fuelie600]

I apparently am short on signal strength. I am currently using the tach lead behind the alternator to operate my Aeromotive fuel pump controller. This signals the controller just fine, and my factory tach still operates. Now, I decide to install a Autometer 5" memory tach. Everything is plugged in---and the new tach works fine........but the FP controller will not pick up a RPM signal, and the factory tach does not operate. Disconnecting the Autometer tach restores the signal to the controller and factory tach. Guess I can not run both items off the same tach signal. What are my choices? Is there another signal source? Is there some type of signal booster/amplifier? Can the factory tach be disabled to reduce draw? Wires are everwhere, and I would like to get this figured out. Any help would be great. Brian

 

[salvageV6]

Pin B on the display connector for the tach. and boost gauge in the dash area is a white wire for the tach. Pin A is a pink/blk power wire and Pin C is a brown wire for proper connector reference. Single row connector A to H I belive on the analog dash.

One would think a buffer amplifier could be used high Z input to low Z drive unity gain non-inverting configuration to drive the new device.

But thats another topic for another day.

And as always the device requirements load information and voltage requirements for signal amplitude would be nice to have first.

 

[Fuelie600]

Pin B on the display connector for the tach. and boost gauge in the dash area is a white wire for the tach. Pin A is a pink/blk power wire and Pin C is a brown wire for proper connector reference. Single row connector A to H I belive on the analog dash.

One would think a buffer amplifier could be used high Z input to low Z drive unity gain non-inverting configuration to drive the new device.

But thats another topic for another day.

And as always the device requirements load information and voltage requirements for signal amplitude would be nice to have first.

Would I need to disconnect only the white tach wire to disable it?

I also located pin B4 @ the ECM plug ( manual describes this pin as ESC ). Was thinking of tapping into this for a tach signal. What are your thoughts?
As always, your a big help with trouble shooting electronics onthese cars.:smile: Thanks, Brian

 

[salvageV6]

Pin B4 on the ECM is the spark timing input, DON'T touch that white wire.

I believe removing the tach. feed to the dash would give you "more power" but how much would depend upon the impedances of the three devices you are trying to drive. Which so far we don't know. And of course the output of the tach. drive itself and it's output impedance.

Disconnecting the white wire should be okay to do, I would probably ground the wire going to the display through a 1K resistor so the input wouldn't float to the tach. Probably no biggy either way but that circuit may not like the open circuit input when you remove or cut the white wire. Easy to do when you are in there. It most likely will keep the display from flashing bars for no reason.

I think a good unity gain voltage follower op-amp. circuit which would be very high impedance non-loading input and a low impedance output would probably be a good drive for the new unit without having to go in the dash.

Building one would require putting my scope on the line and reading the signals and all, and it weighs 40 pounds in my basement and the car is outside in the rain.

Circuit wouldn't require many parts all should be available at radio shack.

Maybe some folks out there know the amplitude of the wave etc. is it a square wave 0-5 or 0-10 or 0-12 volts?

Is it common grounded to the cars ground?

 

[Madcat455]

would something like this work?

Caspers sells a signal amplifier for aftermarket tachs. Maybe this would free up enough for the controller.

May be way off base, but figured I'd put it out there.

https://www.casperselectronics.com/...Product_Code=102007&Category_Code=8687GN_Perf

 

[Fuelie600]

Pin B4 on the ECM is the spark timing input, DON'T touch that white wire.

I believe removing the tach. feed to the dash would give you "more power" but how much would depend upon the impedances of the three devices you are trying to drive. Which so far we don't know. And of course the output of the tach. drive itself and it's output impedance.

Disconnecting the white wire should be okay to do, I would probably ground the wire going to the display through a 1K resistor so the input wouldn't float to the tach. Probably no biggy either way but that circuit may not like the open circuit input when you remove or cut the white wire. Easy to do when you are in there. It most likely will keep the display from flashing bars for no reason.

I think a good unity gain voltage follower op-amp. circuit which would be very high impedance non-loading input and a low impedance output would probably be a good drive for the new unit without having to go in the dash.

Building one would require putting my scope on the line and reading the signals and all, and it weighs 40 pounds in my basement and the car is outside in the rain.

Circuit wouldn't require many parts all should be available at radio shack.

Maybe some folks out there know the amplitude of the wave etc. is it a square wave 0-5 or 0-10 or 0-12 volts?

Is it common grounded to the cars ground?

Holy cow Salvage. You have totaly confused me. I think I know what you want to do, but your speaking Greek to me. I wish I could absorb what you are saying. Anyhow, I checked out the Caspers link, and it looks like their unit it is what I need. What do you think?

 

[Fuelie600]

would something like this work?

Caspers sells a signal amplifier for aftermarket tachs. Maybe this would free up enough for the controller.

May be way off base, but figured I'd put it out there.

https://www.casperselectronics.com/...Product_Code=102007&Category_Code=8687GN_Perf

Thanks for the link. I think that will work. Brian

 

[salvageV6]

That may work for you.

 

[Fuelie600]

To update. Caspers Tach adapter did the trick.

 

[CGASTON]

To update. Caspers Tach adapter did the trick.

I know that this is an old post. But how is this working? Any issues to date?