sb66

hey everyone

I am replacing my tach filter and was strongly considering a relocation as well - I thought I had read others had moved theirs as well - 2 questions I have - 1 - my current filter has 2 white wires, and the new one has a brown and white - does the orientation of these matter?

2 - what size wire can I add when I relocate - I think the filter says 20awg - but it looks as thick as the 18 awg. - 20 has been much harder to find but if that is correct . .

any help is greatly appreciated

Sean

sb66

I guess the other question would also be - how do you get the brown connectors off of the old wires so you can use the shiny new brass wire connections on? or does everyone reuse the old ones?

sb66

brown plastic piece may be called plug connector holds the wire connector inside - maybe some kind of spring action on the wire end?

Joe C

well, looking at the schematic on the attachment drawing, I would say "no," however, the electrical connectors on each end would define the "install" orientation.

aklim

I moved mine to the trash can and joined the wires as necessary.

Hot Rod Roy

That would be a bad guess. This is a "two-element low-pass R-C filter". For the most effective filter performance, the "X" terminal should go toward the distributor.

Using 18 ga. wire is just fine. The wire size makes no difference, but the filter should be located near the distributor for best performance.

For more information: https://www.electronics-tutorials.ws/filter/filter_2.html

Joe C

"bad guess" - wouldn't be the first time , although, i'd like to see the (tach) waveform on a scope. you maybe right, but the way I see it, it's just a second order low pass filter across a 10K resistor. the only thing you are changing is which RC network is the first order, and which is the second. it's been many years and my electronic theory is pretty rusty, but I doubt it would make any difference in either direction. i'm basing this on the fact that resistors are not polarized, the voltage drop across the 10K resistor would be the same either direction as well as any current limiting within the network. caps could care less since they are just cleaning up the waveform and filtering frequencies. then again, I could be wrong. -

sb66

thanks everyone -

I was trying to find a spot where the access would be a little easier - the angle and placement of this is really buried - should I need to get to it again I would rather not have to take the car apart to get there. My understanding is that the body needs to be grounded for this to work properly as well - so if it needs to be close to the distributor - maybe a small metal extension? or I could drill another hole on the bracket it is on now - -- currently it is attached to a bolt at the base of a bracket that extends up and holds a metal tube from the brake booster - wonder if that would still ground it to the block well enough?

sb66

I would like to do that along with much of the lovely emissions stuff that keeps getting in my way

aklim

I did and you can too

sb66

yes thankfully Ohio does not have that whole inspection thing

sb66

I did read somewhere on here that some were able to ditch the filter and be ok - while others had issues - unless they had other issues they were unaware of

aklim

It smooths out the tach but I think it needs to be fully functional or like you said, will have problems

FOURSPEEDVETTE

Mine was easy. I just cut off the two wires on the end of the old filter that was mounted between the fire wall and the valve cover. It was way too hard to try and use the old location to install the new filter. I just left the old filter in its original spot. It's almost hidden anyway. I then spliced a new section of wire to the wires where I cut them off the old filter. I mounted the new filter assembly to one of the bolts holding the thermostat housing in place as it already had a threaded post on it, and spliced the new wire section onto the new filter. I covered the wires with black spiral wire tubing to make it look like a factory job. It works perfectly.

65Z01

A shop in Westchester rebuilt the engine in my prior '88 and failed to connect the tach filter to the top bell housing bolt with the result that the tach was flutter around.
After I simply grounded the tach base to the engine block with a jumper wire she was rock steady, as before.

So I say yea it is essential to have the tach base grounded.

Hot Rod Roy

Again.

Joe, I don't want to dwell on this issue, but I gave you the link to help you see that your perceptions of how "first order/second order" filters work. By connecting the tach filter backwards, it becomes a "first order" filter.

Peace!!

Joe C

sb66

I will watch to see - I am hoping I got the right ends going the right way - what happens if it becomes a first order filter - that doesn't sound good -

sb66

I will look again - I think I left plenty of wire to cut and change if need be - any more than that - and I will move it like fourspeedvette -

sb66

so far so good - thanks for all the help everyone!