Factor

Hi all,

I have a 76 elect tach that was converted into my 69 vette.
The car does not have the tach filter (not sure what this does).

Every once in a while the needle will stick or jump...it is very infrequent, but I am doing a restoration now and figured just fix it.
One person advised a new board.

what is usually advised here?

what does the tach filter do?

Thanks,
Ron

0Willcox Corvette

The tack filter.. and maybe after this post, people will truely understand what it does..

The main purpose of the tack filter is to knock the square off the signal before the signal enters the tachometer.. What is funny about this is the tach board chip is capable of reading it squared or rounded and on both on the original tach boards and the reproduction tach boards.

So is it needed.. there are many people today running tach's without one..

Your sticking needle could be a bunch of causes. It could be a board issue, it could be a terminal issue.

I think I would remove the terminal from the tach connector in the dash and clean it. I would also do the same at the distributor. If the issue continues, then the most probably cause is the board.

Now.. More and more we are seeing failures in the analog movements. As these gauges age, they can and will loose the dampening fluid inside the actual movement. The boards are designed to push for a portion of the needle movement, and then to pull the rest. So what can happen is the needle, without resistance can over-react. Or push over.. We just had a tach in our shop last week with this issue..

IMHO,
Willcox

Factor

Hi Wilcox!!!

Thanks! GREAT info! Makes sense!!!

Will clean up and see!

BTW How does the tach needle come off??

Thanks,
Ron

AirborneSilva

I have a very similar issue, how hard is it to get to the tach connector in the dash?

0Willcox Corvette

The tach needle pulls off, it is friction fit. I have a assorted selection of crab forks I've used for years. I have bent them to accommodate different year needles but it works without any worry of damaging the needle.

On the 1975-1977 cars, the connector is right behind the tach.

AirborneSilva

Thanks Ernie, sounds like I need to get my Gumby on

0Willcox Corvette

Yeah.. Gumby don't play that.. lol. You'll become a member of the inverted dash club.. Just make sure you have oxygen handy. Personally.. I send in a substitute for this job.

AirborneSilva

Yeah don't think I could get the wifey to do it but then again she's always asking if there's something she can help with

Factor

NICE!

Thanks Wilcox!

Factor

by chance...wilcox...would you know if the 69 face would swap with the 76 face?

want it to look correct with my 69...in theory looks like a simple swap...

THnaks,
R

0Willcox Corvette

well.. yes and no... The spacing for the screws vs the rivets used on the 76 face are different. The trick is to make a plate behind the face so that you can rivet the new face on. The stock face with screws is an 1 3/8, the electric tack rivets are 1 5/8 apart.

Willcox

Factor

AWESOME! THANKS! Dimensions/gearing should be fine...looks like same distance on RPM #s....right?

0Willcox Corvette

That will depend on what year you get. You can use the movement from any of the tachometers, but if you get a used one with a working board, make sure it's one from a 1975-1979. The calibration is closer to what you need. 80-82 tach's are calibrated differently.

You would still need to do a zero set on the tach before you installed the needle. I've thought of doing this to some new gauges, but often wonder if there is a demand. The issue is the time required and the cost of new might drive the overall cost up too high.

Factor

Hi Wilcox!

Thanks!

OK! got a 76 for my base to swap the face on.

BTW...does the needle just push on? does it click?

ALSO...how does one do a zero set?

Thanks,
Ron

0Willcox Corvette

Ron.. go to my site and watch the video.. it will show you. Search by year.. 76.. search for "tach" and then look under tech video's. You'll see it and if you don't post back I'll post the link.

Willcox

EasyEd

[QUOTE=Willcox Corvette;1587713654]Ron.. go to my site and watch the video.. it will show you. Search by year.. 76.. search for "tach" and then look under tech video's. You'll see it and if you don't post back I'll post the link.

Willcox


Watched video 3 times before I did my board replacement. Wanted to do it right the first time, and did. Answers a lot of questions. Hardest part was zeroing the needle. Had it close the first time, never did much better after a couple tries. Solved my dead tach problem.

0Willcox Corvette

[QUOTE=EasyEd;1587719110]You'll note.. in one of the zero vids.. I blew it a couple of times.. It's not hard, but sometimes it can be a bear..

Willcox

Factor

Thanks! Great stuff! Watched it three times...
so to Zero...just 12 volts, pull the needle, and reinstall to "0" with the 12 volts on, correct?

what about the dist signal? how do we duplicate this out of the car?

Back to tach filter, in the vid you refer to it alot, but do not say it is unnecessary...? is it needed with the STOCK board?

Thanks!

0Willcox Corvette

You don't need a signal to do a zero set.. Zero is what you are after and without any input.... we'll you have zero..

Power, ground and put the needle on zero...


Willcox

Factor

AWESOME! Will do!

so if I have an original board...is a tach filter necessary?

ALSO, if everything/dash is out, since it is almost 40 years old...do you recommend people replace the boards?

Thanks Wilcox!
Ron