EI Tach isolators

I purchased a used ei tach and it requires isolators going to the mags. Does anyone know what these are? I assume they are resistors. If so, what size?

Also, the EI manual does not say how to reset TT. Do I have to send it off to EI?

It was previously used on a 0360 like mine.

I will call EI Monday, but was hoping to get this done over the weekend.

Thanks in advance.

It has to go back to EI to reset TT. I think mine is wired through the ignition switch and doesn't use isolators ,don't remember for sure about the wiring. 0-320 with Slick mags.

E I Tach

On the road and can't provide specifics, but I have installed a couple E.I. model R1 tachs on Moooneys (IO-360/dual Slicks) and have always installed resistors in the P leads near the key switch. Had tach time reset at E.I.


Don Broussard

RV 9 Rebuild in Progress

Most tachs reading from P leads will need resistors. While they could be built into the unit, it wouldn't seem likely as different sizes could be needed and you would need to be resistor free to read a tach signal from an EI.

Larry

The value of the isolators we include with the R-1 instrument are 79K and 47K ohm. Due to the differences in the mag output, different combinations of isolators are often necessary. I typically recommend starting with the 79K ohm isolator and observe the tach's reading. If it is very jumpy and high, you don't have enough isolation. If it reads 0 at lower power settings and jumpy low, you typically have too much isolation. If you'd like to PM me your address, I'd be happy to ship a package to you at no charge. You would only be responsible for shipping charges.

Had to figure out what the isolators are today. Called Electronics International. They confirmed its just 79Kohm resistors.