....both died as you described .
1976 Tach help
Thread Starter
Drifting
Joined: Jun 2006
Posts: 1,327
Likes: 43
From: Vernon CT
1976 Tach help
Ok… continuing my 76 restore. (I fix 1 thing, 2 things break…)
All of a sudden my tach shows 2500 no matter what, even off. Is the 1976 an electrical tach or mechanical?
With the center gauges out I tried to look in back of the driver's dash pad but the AC duct (or something) makes it impossible..
I don't see anything hanging or lose on the distributor…
Any idea where to start to fix this?
All of a sudden my tach shows 2500 no matter what, even off. Is the 1976 an electrical tach or mechanical?
With the center gauges out I tried to look in back of the driver's dash pad but the AC duct (or something) makes it impossible..
I don't see anything hanging or lose on the distributor…
Any idea where to start to fix this?
Le Mans Master
Joined: Oct 2006
Posts: 6,842
Likes: 285
From: Palmdale CA
I can't claim to know when the C3 went to an electric tach, but I can tell you, that the mechanical is driven off of the bottom of the distributor shaft, right below the cap, but before it goes down into the intake. It is on the drivers side and enters the dash area through a hole in the firewall.
If it's a mech tach, you'll see a thick black cable, about the diameter of your pinky, running through the area I just described. You can unscrew it from the distributor using these gnurled ring, but beware, do not lose the little brass insert that goes in the hole and on the end of the cable!
Now that you have the cable in your hand, you can check to see if it spins freely. You also shouldn't be able to pull it out either, as the other end is locked with a clip into the back of the tach. Assuming it it spins freely, have somebody watch the tach, while you twirl it. You should see the needle move . If you don't, you might have problems with tach or the other end of the cable.
If it's a mech tach, you'll see a thick black cable, about the diameter of your pinky, running through the area I just described. You can unscrew it from the distributor using these gnurled ring, but beware, do not lose the little brass insert that goes in the hole and on the end of the cable!
Now that you have the cable in your hand, you can check to see if it spins freely. You also shouldn't be able to pull it out either, as the other end is locked with a clip into the back of the tach. Assuming it it spins freely, have somebody watch the tach, while you twirl it. You should see the needle move . If you don't, you might have problems with tach or the other end of the cable.
Safety Car
Joined: May 2008
Posts: 3,747
Likes: 713
From: Lafayette Louisiana
My 2 cents...
Electronic tach came with the HEI distributor (no points) starting in 1975. If you have an original setup with HEI, which is likely I would guess, then you have a electronic tach. On my 76, the electronic tach went out, so I had to pull the dash and replace the "tach circuit board" behind the tach. Good to replace the tach board and the filter at the same time. The filter is a small cylinder (think it is a condenser) mounted on the intake right next to the carb. The tach boards for these years are not too good, so I would bet yours just went bad. Wilcox has a nice write up on this in his tech papers (thanks!) hope this might help.
Oh can relate to the 1 step forward and 2 back days, but this forum is great and much thanks to all.
Oh can relate to the 1 step forward and 2 back days, but this forum is great and much thanks to all.
Last edited by 20mercury; Sep 13, 2014 at 03:24 PM.
Le Mans Master
Joined: Oct 2006
Posts: 6,842
Likes: 285
From: Palmdale CA
Electronic tach came with the HEI distributor (no points) starting in 1975. If you have an original setup with HEI, which is likely I would guess, then you have a electronic tach. On my 76, the electronic tach went out, so I had to pull the dash and replace the "tach circuit board" behind the tach. Good to replace the tach board and the filter at the same time. The filter is a small cylinder (think it is a condenser) mounted on the intake right next to the carb. The tach boards for these years are not too good, so I would bet yours just went bad. Wilcox has a nice write up on this in his tech papers (thanks!) hope this might help.
Oh can relate to the 1 step forward and 2 back days, but this forum is great and much thanks to all.
Oh can relate to the 1 step forward and 2 back days, but this forum is great and much thanks to all.
Thanks for chiming in! I have a '74 and now I know, cool and yes, this forum is great!!!
Burning Brakes
Joined: May 2013
Posts: 789
Likes: 129
From: Los Banos CA
I just repaired the elec tach in my 79 (this weekend actually), but the symptom sounds different. Mine would read 0 RPM with the car off, but would redline as soon as the engine started. I found some info on a resistor that goes bad on the circuit board, so I replaced it with a potentiometer (variable resistor), verified that it functions normally now, and will be calibrating it tomorrow (didn't have time to dig out a stand-alone tach to synchronize it to).
If I didn't already have the parts on hand, I would have probably just bought the whole board from Willcox (An A#1 vendor in my book!)
If I didn't already have the parts on hand, I would have probably just bought the whole board from Willcox (An A#1 vendor in my book!)
Pro
Joined: Jul 2010
Posts: 691
Likes: 25
From: Boynton Beach Florida
All you need is the tach circuit board but most importantly, order the correct one for your year and make sure it states to already be Calibrated. Several vendors sell a board that isn't calibrated and won't work and with as much fun is involved with installing this you want to get it right the first time. I had to do the job twice since I didn't know about the calibrated versus non-calibrated until afterwards. This was several years ago so maybe they are all correct now but just wanted to let you know. Mine still works fine.
Eric
Eric
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