Tach gone all screwy
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Joined: Feb 2005
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Tach gone all screwy
alright got the 78 circuit board and installed it, but now every time it works, its almost like it has an exponential growth. Idle looks right, but on the choke it says its at like 2800, and with a little gas its redlined. whats up and how do i fix this. 2nd and off topic does anybody have suggestion for a good pair of tires and shocks. the rims are stock 15 in 
Racer
Joined: Sep 2004
Posts: 389
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From: Sayreville New Jersey
I have 255/60/15 Hoosiers on my '78 also witht he stock aluminum wheels. They were on it when I bought it almost 2 years ago. They fit and look great. No rubbing and I need new shocks too. My car is a daily driver doing 50+ miles everyday of the year in NJ. When my tires need replacing I'm planning on replacing with the same size tires using Firestone Firehawks. I've had great success with them in the past. They are good tire for driving in all kinds of conditions, handle great and wear like stone. Tire Rack .com has good prices and you can compare their ratings against comparable tires. Can't help you with the tach but I'sure someone else will come in. My tach does not work at all. I checked the circuit board awhile back when I had to replace the headlight switch and found breaks so I'm assuming that's my problem. I also have the new one and am planning on installing soon. Did you lower your steering column to pull the speedo/tach out? If yes, was that easy to do? I did not the last time I pulled the speedo/tach out and had a difficutl time getting it out and reinstalling. 
KEEP DRIVING!!!
KEEP DRIVING!!!
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alight this is something i learned after the fact. you really dont need to take the whole assembly out. just take off the plastic shielding. Takes like 4 screws and 10 seconds. and yess i think that requires to lower the steering collom, but really thats no big deal. then there is a plastic frame around the tach and spedo. Takes like 6 hex bolts. take that out. then pull of the tach and i think it has 4 screws. straight off and replace the curcuit board. make sure you know what goes where. I assembled it slowly making sure all the insulators were in place. That may sound like alot, but once you get started its just like what a 10 min job. i hope it works for you. I am getting tired of having a off tach like that.
Le Mans Master
Joined: Jan 2003
Posts: 6,575
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From: Tuttle OK
Cruise-In VIII Veteran
Originally Posted by Hwy St*r
Did you lower your steering column to pull the speedo/tach out? If yes, was that easy to do? I did not the last time I pulled the speedo/tach out and had a difficutl time getting it out and reinstalling.
Le Mans Master
Joined: Oct 2004
Posts: 5,269
Likes: 54
From: Orlando Florida
St. Jude Donor '05
Originally Posted by Maco78
i think i wana go with the 255/60/15 for tires so if anyone has had a bad time with those tell me. if not what shocks would you go with.
Shocks: for a daily driver the KYB Gas-a-just shocks are a good deal for $150. These are not sport shocks, very comfortable ride....Everybody seems to be very happy with the Bilstein shocks for $250.
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Race Director
Joined: Sep 2002
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From: San Diego - Deep Within The State of CONFUSION!
Originally Posted by Maco78
does anybody have any follow up on the tach though?
Even took it to the local Speedo-Tach place and had them verify it worked fine. He showed me on the bench, hooked up to the Signal Gen machine.
I took it home, buttoned up my dash and started it up. Just like yours, it reads high as heck. 70MPH and it reads 4800RPM and at idle it shows 1500 even though the idle is set to 800 with my digital timing light.
Instructor
Joined: Jan 2000
Posts: 163
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From: Fullerton CA
Had same experience in my '80. Replaced the tach board first, but didn't totally solve the problem. Ended up replacing the tach filter too. This solved the problem, and it's never returned. Tach filter replacement is an easy ten minute job in the engine bay.
Team Owner
Joined: Apr 2001
Posts: 54,204
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From: S.W. Ohio. . . . . . NRA Life Member
FYI; I will calibrate and test any C3 electronic tach for $45 including return shipping; using the exact same procedures that GM required.
I used to repair them for GM... when they were STILL UNDER WARANTY !!! But, I'm not old... hee-hee
I can also convert mechanical C3 tachs to electronic - and use your original face and needle... as a stealth install. And I don't alter the original face or needle either - so you can always transfer them back to your original mechanical meter movement.
email me for more info:
tim-yvonne@juno.com
I used to repair them for GM... when they were STILL UNDER WARANTY !!! But, I'm not old... hee-hee
I can also convert mechanical C3 tachs to electronic - and use your original face and needle... as a stealth install. And I don't alter the original face or needle either - so you can always transfer them back to your original mechanical meter movement.
email me for more info:
tim-yvonne@juno.com
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
If you haven't replaced the tach filter yet, try that. You may find one on eBay. There are often tach filters for sale from mid-80's monte carlos, olds and buicks that were equipped with Tachs. Direct replacement.
Solved my problem with a tach filter replacement. They do wear out. I also tried fabricating one using parts from Radio Shack but they only lasted about a year (vibration, heat, dirt and lubricants tend to destroy them).
Tach filter for sale on eBay for around $20. Good price. (1 day and 1 hour remaining):
http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW
You can also buy NEW from Ecklers for $60:
http://www.ecklers.com/product.asp?p...RKB9L3CT12AW5D
Solved my problem with a tach filter replacement. They do wear out. I also tried fabricating one using parts from Radio Shack but they only lasted about a year (vibration, heat, dirt and lubricants tend to destroy them).
Tach filter for sale on eBay for around $20. Good price. (1 day and 1 hour remaining):
http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW
You can also buy NEW from Ecklers for $60:
http://www.ecklers.com/product.asp?p...RKB9L3CT12AW5D
Last edited by TedH; Mar 9, 2005 at 09:21 PM.