Another tach question... (Willcox?)
#1
Pro
Thread Starter
Another tach question... (Willcox?)
Hi,
I have a 75/76 tach in my 69 with HEI. It has a home made tach filter installed. This has just been installed to replace the mechanical tach.
Problem is... it fluctuates wildly from zero to full scale while cranking but settles instantly and reads correctly once engine starts.
Where should I start looking? This doesn't seem normal. A search on the forum hasn't got me anywhere.
TIA and
Joe
I have a 75/76 tach in my 69 with HEI. It has a home made tach filter installed. This has just been installed to replace the mechanical tach.
Problem is... it fluctuates wildly from zero to full scale while cranking but settles instantly and reads correctly once engine starts.
Where should I start looking? This doesn't seem normal. A search on the forum hasn't got me anywhere.
TIA and
Joe
#2
Hi,
I have a 75/76 tach in my 69 with HEI. It has a home made tach filter installed. This has just been installed to replace the mechanical tach.
Problem is... it fluctuates wildly from zero to full scale while cranking but settles instantly and reads correctly once engine starts.
Where should I start looking? This doesn't seem normal. A search on the forum hasn't got me anywhere.
TIA and
Joe
I have a 75/76 tach in my 69 with HEI. It has a home made tach filter installed. This has just been installed to replace the mechanical tach.
Problem is... it fluctuates wildly from zero to full scale while cranking but settles instantly and reads correctly once engine starts.
Where should I start looking? This doesn't seem normal. A search on the forum hasn't got me anywhere.
TIA and
Joe
#3
Pro
Thread Starter
#4
Former Vendor
Member Since: Aug 2006
Location: Jeffersonville Indiana 812-288-7103
Posts: 76,656
Received 1,813 Likes
on
1,458 Posts
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Your car will drop while cranking..
Where is your 12 volt power going to the tach coming from?
The Home Made filter is interesting... The filter is designed to knock the edge off the square signal coming in from the distributor. Oddly enough though, the chip on the factory board and on our reproduction board can read either the square or rounded signal... so I doubt this is your issue.
Willcox
#6
My 82 Corvette tachometer hasn't worked in about 25 years. I replaced the tack filter and that didn't fix the problem. I then replaced the circuit board from Ecklers and that didn't fix the problem. The needle bounces around at random. I lived with the problem for a long time and decided to sell the car. I want to get the tachometer to work so I bought a Willcox circuit board from Ecklers and installed it per Willcoxes video instructions. The tachometer still didn't work so I tried bypassing the tach filter. That smoked my tachometer and now the needle does not budge at all. I just want to warn others that bypassing the distributor output filer may not be a good idea
#7
Former Vendor
Member Since: Aug 2006
Location: Jeffersonville Indiana 812-288-7103
Posts: 76,656
Received 1,813 Likes
on
1,458 Posts
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
My 82 Corvette tachometer hasn't worked in about 25 years. I replaced the tack filter and that didn't fix the problem. I then replaced the circuit board from Ecklers and that didn't fix the problem. The needle bounces around at random. I lived with the problem for a long time and decided to sell the car. I want to get the tachometer to work so I bought a Willcox circuit board from Ecklers and installed it per Willcoxes video instructions. The tachometer still didn't work so I tried bypassing the tach filter. That smoked my tachometer and now the needle does not budge at all. I just want to warn others that bypassing the distributor output filer may not be a good idea
The purpose of the tach filter is to knock the edge off the square signal from the distributor before it hits the tach.... and prevent voltage spikes from hitting the board.
The tach board (even the original GM board) is designed to read both the square and rounded signal so removing the filter for testing shouldn't hurt the tach board.
However if there is another issue such as a defective coil in the distributor, or a defective analog movement then you might have an issue... Our boards have a fuse built into them so if the fuse is blown on the board then there is something else wrong with the car. The best thing you can do at this point is send me the tach and the board and I can test them. If the fuse is blown it's 14.00 to fix... if the movement is bad I can tell you in about 30 minutes. So if you are interested in this email me at service@willcoxcorvette.com.
Willcox
#8
Heel & Toe
Member Since: Jul 2018
Location: Findlay Ohio
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
Willcox Corvette, I just purchased a 75 coupe and the Tach does not work. So if I am reading this correctly, if I replace the old Tach board with a new Tach board from Willcox, I dont need to hook up the old filter?
Just want to make sure that I don't need to purchase a filter also.
Thanks,
Bill
Just want to make sure that I don't need to purchase a filter also.
Thanks,
Bill
#9
Former Vendor
Member Since: Aug 2006
Location: Jeffersonville Indiana 812-288-7103
Posts: 76,656
Received 1,813 Likes
on
1,458 Posts
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Willcox Corvette, I just purchased a 75 coupe and the Tach does not work. So if I am reading this correctly, if I replace the old Tach board with a new Tach board from Willcox, I dont need to hook up the old filter?
Just want to make sure that I don't need to purchase a filter also.
Thanks,
Bill
Just want to make sure that I don't need to purchase a filter also.
Thanks,
Bill
Willcox
#10
Heel & Toe
Member Since: Jul 2018
Location: Findlay Ohio
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
#11
Former Vendor
Member Since: Aug 2006
Location: Jeffersonville Indiana 812-288-7103
Posts: 76,656
Received 1,813 Likes
on
1,458 Posts
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
We had a fella send his tach in the other day, he purchased a China made board with washers, he had the original board and then he purchased our board... nothing made the tach work... turns out the analog movement was the issue and when this happens the only fix is ti replace the tach. Unfortunately the only reproduction tach is made over-sea's and this tach has multiple commons unlike the original... so we tweaked our boards (because eventually these will fail too) so that we could fix either the original tach's or the imported ones. Original boards used sine and co-sine with a similar common, repro's don't. Reproduction boards imported are not fused nor are the new replacement tachometers. All our boards are fused, even the low fuel warning modules as well as the delay timers. This prevents damage to the board, it prevents damage to the car and it makes for something that can be repaired cheaply if there is any issue.
If you have replaced your tach board and the tach isn't working my suggestion is to go to our tech page first and try to figure the issue out.. and if you can't send us the tach and board and we'll put it on our test machine to see where the issue is.
Willcox.