tom33

Just received a new Willcox Tach Board today for a 78 Zero'd it out per the instructions on Willcox's site & installed. When I cycle the key it will cycle to zero but once I start the engine the needle pegs. Am I dealing with a new bad board? I replaced my original circuit board because it was burnt in numerous areas.

Thanks
Tom

carriljc

I don't remember how tight it is behind the dash for a 78 as compared to my 68, but if your old tach was working, then perhaps you can run the leads from behind the dash (or even fabricate an extension) to an aftermarket tach (borrow one somewhere?) to see if it reads correctly.
I actually tested my electric tach outside the dash before I installed it - because I was afraid of running into something like this. Depending on results then you may be able to determine whether it's the installed tach or if you disturbed some of the wiring going to the new tach board.

DUB

Tom,
Contcat WIllcox dn elt tehm knwo what is going on.

I know that when I do them....not knowing if the Willcox tach board is different....

I have the ignition key ON and verify that I have the needle set to zero...then turn off the key and the needle goes up slightly. Then when I turn on the ignition again the needle goes to zero and when I crank and run the engine the needle is correct.

And I also have previously verified that the three circuits that go to the tach are correct. One of them is 12 volts (pink wire), one being the ground (black wire)..and the last one is the circuit from the HEI...which can be a tan wire in most cases.

DUB

tom33

Dub,

I have already contacted Willcox & instantly received an email basically saying

"Please do not call our sales staff about technical questions.

With the current volume of questions in regards to repair and installation help exceeding my human ability! I will attempt to answer most questions as time permits"

The tach moves to "0" with the ignition on & moves up very little when the ignition is off. When I start the engine the needle pegs...if I rev the engine there is no change. I have already checked power and ground & both are good. Bypassed the filter with no change. Any other ideas?

tom33

78' isn't to involved to do. Basically the lens & a trim panel. I didn't install the trim or lens yet just the tach. There is really nothing there to be disturbed...just sort of plugs in. However I did already check power & ground there & it's good. My old tach is burnt and in operational as far as borrowing one that's not really an option for me. Thank you for the insight though

carriljc

Have you gone through the Willcox troubleshooting guide? http://repairs.willcoxcorvette.com/c...ink-1978-1982/

tom33

Yes. I have checked the fuse, bypassed the filter, checked power, ground and continuity multiple times. I have a print out on the trouble shooting guide and performed each step twice. As well as zeroing the tach according to Willcox video. The tach I ordered is already calibrated & ready to install per Willcox's instructions. Hopeful I've just overlooked something & I'm not dealing with a tach circuit board issue.

carriljc

Seems like you've done a lot.
One thing I would try (maybe because I don't trust myself) is to run a separate independent lead from the tach output to the tach..... just for sh*ts and grins..... Since you said you already checked Power and Ground, then this would be a thing to try. Can't hurt and it should be relatively easy.

7T1vette

What was the tach doing before you bought the new circuit board? If it is acting the same as before, I suspect your problem is in the 'signal' coming to the tach board. Perhaps the signal wire is damaged, etc.

Heus

I'm having a similar issue with a new Willcox tach board. From a previous thread
"Im suddenly having problems with my tach not working as well. Even after installing a new tach board from Willcox it stays stuck at 5500 rpm. I verified power, ground, and tested the continuity of the signal wire as per Willcox's instructions and all are fine. It does not have a tach filter. "

tom33

7T1vette,
The old tach board circuit is burnt. It would not operate at all. No needle movement just sets all the way at the bottom below "0" . The new tach moves when the key is cycled on will move to "0" & when off will go just a notch above. Once the engine is started it basically pegs & will not move even if I rev the engine. I checked the old circuit board again last night and it is dead - it does absolutely nothing...checked the new board the same way it is able to be "zero"d. I've also checked the signal wire for continuity it is within range.

DUB

I am NO expert...but my logic skills and deductive reasoning tell me that if the ground is good....and the power is good going to that tach is good...and the wire from the coil of the HEI is good...and the tach goes to '0' when the key is ON...and when the key is OFF the tach needle goes up a bit...and when you crank the engine and it goes nuts...it is the tach board. And that is assuming that the tach board is installed correctly...which I feel that is not hard to do correctly.

And reading what you wrote..I knwo when I can checking the wire from the distributor cap that is for the tach..I have it disconnected for the distributor cap and or teh tach filter and also I have the tach out or the connector removed from the speedo/tach cluster and check that wire and make sure it is not grounded anywhere or picking up power from somewhere.

I do not know if the tach boards from WIllcox are like the ones I get where the tach filter is not required.

DUB

Heus

"I do not know if the tach boards from WIllcox are like the ones I get where the tach filter is not required."
DUB this quote got me thinking. My new Willcox tach board did not help my problem. I do not have a tach filter. Could this be why the new board didnt work? As I said previously I have power, good ground, and continuity from the distributor.

zwede

It's possible the new board is bad. It's also possible the old board fried one of the coils in the needle movement when it went out. The movement has 2 coils and it will still read 0 with only one coil working.

Lack of a tach filter should not cause the problems you're seeing.

DUB

I believe the current technology of how these tach boards are being made do not require the filter.

DUB

tom33

UPDATE: After testing all the components multiple times - The tach started working & I haven't been able to get it to not work again to know what the issue was. It has been working perfectly for the past few days.

0Willcox Corvette

Tom... The email says to contact support@willcoxcorvette for technical questions??? I've not seen an email from you at this address and I monitor it daily.

When a tach pegs as you described, in most cases the issue is either one of the nuts on the board is not getting good contact.

We had a customer last week that sent us his tach in and the nuts were so corroded that there was no way the would pass continuity without being replaced.

So you understand... if you don't have one of the nuts all the way tight making good contact the board will only read one side. There are two sides to the board signal out of the chip... sine and co-sine.

When the board functions, the sine pushes and the co-sine pulls until the board reaches approximately 2500 rpms.... then they flip and the sine pulls and the co-sine pushes... but if one nut is not making good contact then it will only read the other side when the ignition switch is turned on and thus the board will either go below zero or it will peg out depending on which nut is the issue.

If you ever have a question about something we make.. Sales has some knowledge but not enough to answer your question (thus the auto reply). But you can contact me anytime at support@Willcoxcorvette.com (as long as it's not a wiper motor issue.. )

Now in regards to the filter.. Our board will run without the filter as will the original GM boards. The filter knocked the square off the signal and helped prevent voltage spikes. But the boards (even he original boards) were designed to read both square and wave so they will both function with or without the filter. But... .it's a smart idea to run the filter to avoid any voltage spikes.

So.. possibly the nut made good enough contact to roll, but I suspect the issue will return. If it does, I would remove the tach, back off the nuts just a tiny bit and then re-torque them to see if the problem goes away.

Willcox

tom33

Thank you for the response. I will try the re-torque if the problem returns.

As far as emailing support my email was sent on September 5th to support@Willcoxcorvette.com & I received an automated reply instantly with both emails I sent. If you would like I can forward those emails to you showing that the generated message was from "support" and not sales. The beginning of the auto reply started "Thank you for contacting our support team." I just wanted to make you aware in case this is not the way it should be set up.

Once again though thank you for the information on the re-torque of the nuts! The information in greatly appreciated because as you said the issue will probably return.

0Willcox Corvette

Tom.. I just checked my email files.. I don't see it. Now I've got a new project.. figure out why?.

Ernie