Mechanical Tach Repair?
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Mechanical Tach Repair?
My tach had been rather bouncy, now it is rock steady at 2500rpm even when the engine is off! I am so pleased to have it break now after I put the dash all back together :mad
Do they make rebuild kits for tachs? The nearly $300 for a replacement from Ecklers is a bit steep.
What have you guys done, or is mine the first one to break?
Chuck
Do they make rebuild kits for tachs? The nearly $300 for a replacement from Ecklers is a bit steep.
What have you guys done, or is mine the first one to break?
Chuck
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Re: Mechanical Tach Repair? (Chuck Harmon)
Chuck, I don't think muchof mechanical tachs...but here goes....
it's the same mechanism as a speedo, but without the odometers....
differant calibration of course....
but the machinery is the same.....
so you need get it outta the car again....on the kitchen table with small tiney screwdrivers, and a CLEAN work surface....take the thing apart including the large up and over bent aluminum piece you see after taking the face plate off, the pointer just pulls off with a lot of force on your fingertips....don't pry it, you will kill something....
there are two screws holding it to the casting....
lightly lube...I used WD40....the input bearing and the front needle bearing on the cup....done....
make sure it's damn clean and stays that way, on assy.....
easy to get dust into it, and watch the old crumbling light box padding,....
GENE
it's the same mechanism as a speedo, but without the odometers....
differant calibration of course....
but the machinery is the same.....
so you need get it outta the car again....on the kitchen table with small tiney screwdrivers, and a CLEAN work surface....take the thing apart including the large up and over bent aluminum piece you see after taking the face plate off, the pointer just pulls off with a lot of force on your fingertips....don't pry it, you will kill something....
there are two screws holding it to the casting....
lightly lube...I used WD40....the input bearing and the front needle bearing on the cup....done....
make sure it's damn clean and stays that way, on assy.....
easy to get dust into it, and watch the old crumbling light box padding,....
GENE
Safety Car
Joined: Jan 2000
Posts: 4,143
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Re: Mechanical Tach Repair? (Chuck Harmon)
Yeah, I agree with the procedure.... :)
...Also, make sure your 'cable' is well lubricated & if it's original, then you might want to replace it.
My tach had a 'jumpy' needle and used to stick.... then the needle broke after it got caught (cable locked up) and revvved to 9000 ! (no, not my engine, just the tach) :eek:
'course now I'll have to disassemble my tach to replace the needle, ouch ! :(
Good Luck, man ! ...also check eBay periodically, you might get one cheaper than $300 that works & then you'd have an extra.
...Also, make sure your 'cable' is well lubricated & if it's original, then you might want to replace it.
My tach had a 'jumpy' needle and used to stick.... then the needle broke after it got caught (cable locked up) and revvved to 9000 ! (no, not my engine, just the tach) :eek:
'course now I'll have to disassemble my tach to replace the needle, ouch ! :(
Good Luck, man ! ...also check eBay periodically, you might get one cheaper than $300 that works & then you'd have an extra.
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: Mechanical Tach Repair? (mrvette)
Gene,
Thanks for the quick reply. What would have made the tach bouncy in the first place? Is there a damper of some kind? Or is bouncy"ness" just the result of dirt?
Thanks,
Chuck
Thanks for the quick reply. What would have made the tach bouncy in the first place? Is there a damper of some kind? Or is bouncy"ness" just the result of dirt?
Thanks,
Chuck
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Re: Mechanical Tach Repair? (Chuck Harmon)
Chuck, the bouncyness is caused by anything from dirt, light box 'lint' which you will see upon taking tach assy apart, and also dried oil, especially on that silly bearing you can't see untill the last bracket is removed when taking the aluminum 'cup' off the spinning magnet.....careful of the tender coil spring, looks like a hotplate on an electric stove....
take your time, drink a beer, get good light, clean place, kitchen table, toss haus frau out of the house for a while, and have at it....
I bet your stuck now from just dirt, hopefully not damaged....
DO NOT USE AN AIRJET FROM COMPRESSOR TO CLEAN IT, YOU WILL BLOW THAT POOR SPRING ALL TO HELL.....
take your time, drink a beer, get good light, clean place, kitchen table, toss haus frau out of the house for a while, and have at it....
I bet your stuck now from just dirt, hopefully not damaged....
DO NOT USE AN AIRJET FROM COMPRESSOR TO CLEAN IT, YOU WILL BLOW THAT POOR SPRING ALL TO HELL.....
Melting Slicks
Joined: Feb 2001
Posts: 3,330
Likes: 13
From: Europe , Luxembourg
Re: Mechanical Tach Repair? (Chuck Harmon)
Hi
My 68 big block tach also became bouncy last year and specially at idle.
It bounced that much that the needle hit the zero stop hard and broke off. :mad
It ended up with a good cable lubrication and now it's like new.
Go for the cable, there is nothing in the tach mechanisme that can make it bounce. This happens due to wound up cable, like a sping that releases all of a sudden.
Good luck, it's not so easy to get to the tach without prying the panels to their limit. :cry
Gunther :seeya
My 68 big block tach also became bouncy last year and specially at idle.
It bounced that much that the needle hit the zero stop hard and broke off. :mad
It ended up with a good cable lubrication and now it's like new.
Go for the cable, there is nothing in the tach mechanisme that can make it bounce. This happens due to wound up cable, like a sping that releases all of a sudden.
Good luck, it's not so easy to get to the tach without prying the panels to their limit. :cry
Gunther :seeya
Safety Car
Joined: Feb 2000
Posts: 4,977
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From: Massachusetts , USA,
Re: Mechanical Tach Repair? (Chuck Harmon)
Try a new cable first,,,,,,,,,,,, :smash: , they are cheap & dont have to fool around with old nasty :crazy: cable........then see what happens
Le Mans Master
Joined: Aug 2000
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From: Semper ubi, sub ubi
Cruise-In VI Veteran
Cruise-In VII Veteran
Re: Mechanical Tach Repair? (Chuck Harmon)
I'll agree with changing the cable, check your distibutor crosshaft gear when you change the cable.
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Re: Mechanical Tach Repair? (Chuck Harmon)
Something else to look at. If the inner cable is a bit too long, it can push on the back of the tach assembly and cause the needle to stick. I was told that grinding off a little bit of the end of the inner cable will fix the problem. It may also fix the jumping. The problem is, the inner cable is inserted from the tach end. That means you have to remove the dash to fix this problem. That's why mine occasionally sticks or bounces. :rolleyes:
Thread Starter
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: Mechanical Tach Repair? (john73bb)
Thanks for all the replies, guys. The cable is brand new, but slightly too long, even though it is the corect #. I wish it were closer to 2 inches shorter. I may have to drill new hole through fire wall to allow less stressed fit.
Chuck
Chuck
