Stewart Warner Tachometer Will Not Read Through Firewall / Adjust Question

Hey guys, I have a strange problem with my Stewart Warner tachometer. I "bench tested" it using jumper wires connected to all components inside the engine compartment, and it seems to read just fine. I did all the same hook ups by running wires through the firewall and I get no reading whatsoever. What gives?


And, if possible, I would like to know how or which way to adjust the potentiometer shown to allow for 8 cylinder operation. It's model number 997RV6V







Thanks!

 

Any ideas?

 

Do you have a dwell meter with a tach function? If so, hook it up and see where you're idling at then temporarily hook up the stewart warner and switch the potentiometer until it matches. I don't think you'll hurt the SW tach by having it in the wrong position, it just won't read accurately is all.

 

I don't have that model SW tach, but I can look at the back of my new SW Greenline tach to see what it looks like (either tonight or Fri night).

 

Thanks guys. New Problem has arisen. I have a strange problem with my Stewart Warner tachometer. I "bench tested" it using jumper wires connected to all components inside the engine compartment, and it seems to read just fine. I did all the same hook ups by running wires through the firewall and I get no reading whatsoever. What gives?

 

Any suggestions guys?

 

Sorry, I was waiting for the new problem that had arisen post. I'll look at the back of my tach tomorrow. Have you tried calling Stewart Warner?

 

Oh sorry about that. I ended up editing the original post. But I fixed it now so both are edited. But no, I haven't tried them. You think they'd have info on this old thing?

 

You state that the tachometer works when bench testing, but fails when it is installed in the car. Are there other wires passing through the same firewall port with the tachometer wring?

I used to work with low voltage circuits in CNC machinery and low voltage DC current can create noise (RF) on other circuits that are in a close proximity thereby causing unpredictability of functions.

Try rerouting the wiring.

McGurk

 

Maybe you lost the grd when in the car, if the light doesn't work that would be a clue..