Author Topic: Tach-ling the Tachometer  (Read 2533 times)

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Offline pwrcat4000

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Tach-ling the Tachometer
« on: November 03, 2011, 02:09:41 AM »
Well tonight I started working on the small stuff as my Body work is stalled right now until I teach my self to weld sheet metal.
My tachometer had been working until after the engine rebuild then it failed. I was unsure if it was wiring or the actual 35 year old tachometer, as you all know I have no money at all so I am forced to try and fix things on my own.  If you have the cash
 Option #1 this is the best way to go They come highly recommended and were only going to charge a little under $180.00 plus shipping both ways.

Option #2 Here is another way to go BRAND NEW $277.99

I chose option 3 fix it myself. I recently acquired a broken 50 inch plasma screen some one gave it to me and said "it wont turn on and its out of warranty I bought a new one you want it?" I was able to fix it as it was just the power supply and needed about 8 $0.25 capacitors paid a guy to solder them in and Walla!  $60 50" HD plasma screen. I may be pretty dumb but I can read and learn on occasion.

So... here is what I have done.
First


got the clock working luckily I have a 12V power source so I know it works now.
 I followed Gold78Spc instructions to a T (/A) LOL. they are here although I used WD40 not 3-1 oil and did not clean the contacts It is keeping time about as good as a non Quartz clock from 1978 does, I'm told.  It has been hooked up for about 5 hours now and has not lost or gained time. You can update it to Quartz movement the same people who are in Option #1 above (as a matter of fact they can fix all the gauges, calibrate them, and reface them ect.)
Second
I disassembled the Tachometer



and removed the circuit board out of the Tachometer.



I don't have the skill or equipment to test this board so I am going down to the electronics store (where I bought those capacitors for the TV) tomorrow to beg for help. I suspect the   0.068F Radial Film Capacitor is to blame that is the thing that looks like a cigarette butt.  I think the replacement will work even though it is not made the same way it has the same rating and better tolerance.

 

(they use them in guitars too according to google).  Hopefully he can get the Circuit working or sell me the parts and I will take it to the guy I had fix my TV board.
So You are probably wondering how I know this is the problem with no electronics tools.  Honestly I don't. But here is what I have done to rule out the problem.

Bought a brand new printed circuit for the whole gauge cluster it was about $85.00 mine was shorting against the bezel and I had no interior dash lights.

Bought an after market tach from O'Reilly $38.00. plugged it into my tach leads that would be under my dash (if it was in the car), started the car, tach worked so ruled out any wiring /ground issues in the 35 year old wiring. Returned the tach to O'Reilly (don't worry they have made a ton of $ off of me) So it has to be the tach.

Next took apart the tach as stated above. 



There were 2 wires hooked to the circuit board in question a white one (+) and a black one (-) the polarity really doesn't mater if you hook it up backwards your tach will try to go backwards.  I hooked up a AAA battery to this for a millisecond the needle deflected so that part works the only thing between those wires and the leads from the car is that Circuit board So that has to be the problem.
I will post a follow up when I get the circuit evaluated/fixed.
Hope this helped someone (Lot of typing)
« Last Edit: October 18, 2019, 12:06:48 AM by pwrcat4000 »
My 1978 T/A the only thing that I ever loved that didn't leave me (Yet)

Y88

Offline skisix38off

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Re: Tach-ling the Tachometer
« Reply #1 on: November 03, 2011, 08:25:08 AM »
That great you got your part working and did it on your own!  More power to you!  The whole thing on the clock has pushed me over the edge- I'm going to pull my dash out and do some work in there- including making my clock work.  It turns over every once in a while now so I think my problem is the electrical contacts somewhere but reading this has inspired me to go fix it.

Thanks!

Great looking '78 Y88!!!
1978 Y88 L78 auto, PW
Greg

Offline RENOVATIONS

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Re: Tach-ling the Tachometer
« Reply #2 on: November 05, 2011, 09:30:15 AM »
Thanks for posting this...very good info and hopefully it will help others.
I'm going to move this to the "electrical" section where others can see it
Jeff

Projects:
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1978 Trans Am
1970 Camaro
1970 'Cuda

Offline pwrcat4000

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Re: Tach-ling the Tachometer
« Reply #3 on: November 08, 2011, 06:00:47 AM »
Well no luck local parts store so I ordered a capacitor online Still may go with option one if that doesn't work
My 1978 T/A the only thing that I ever loved that didn't leave me (Yet)

Y88

Offline pwrcat4000

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Re: Tach-ling the Tachometer
« Reply #4 on: November 14, 2011, 12:13:41 PM »
Ordered the wrong capacitor the thing was as big as my thumb and .68uF.
I needed 0.068uF it is on order now
So far under 20.00 but it is not fixed yet.  Still may go with option #1 this is the best way to go They come highly recommended and were only going to charge a little under $180.00 plus shipping both ways.
Part number in the original post IS WRONG FOR SURE
but I think this is the correct one

I will post results later
I will also try to correct the original  post.
My 1978 T/A the only thing that I ever loved that didn't leave me (Yet)

Y88

Offline pwrcat4000

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Tackling the Tach FAIL!
« Reply #5 on: December 08, 2011, 03:38:15 PM »

Soldered this in and it still dont/wont work so I am shipping it off to Gentry
option #1 this is the best way to go
« Last Edit: October 18, 2019, 12:07:56 AM by pwrcat4000 »
My 1978 T/A the only thing that I ever loved that didn't leave me (Yet)

Y88

Offline pwrcat4000

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Re: Tach-ling the Tachometer
« Reply #6 on: October 18, 2019, 12:11:19 AM »
should have included this in the original post
My 1978 T/A the only thing that I ever loved that didn't leave me (Yet)

Y88