Tach woes - Team Camaro Tech
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post #1 of 14 (permalink) Old May 3rd, 05, 03:44 PM Thread Starter
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Kevin
 
Join Date: May 2004
Location: Kansas
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Tach woes

I have done a search to try and find answers to my questions and a new question has arose.

I have a 68 and I am trying to install a factory style tach, my car did not originally have one. I bought a brand new harness to include this addition. The tach is not new, it was bought off EBAY and I did so knowing that it may or may not work

The brown wire is connected to the negative side of the coil. My tach will sometimes register at about 300 rpm but never moves at all. I am checking to see if I have it grounded correctly. Just to note, the clock in the tach DOES work as does the red bright light indicator in the center of the tach and speedometer gauge.

In a previous post it stated that the top post, behind the tach where there are 3 in a triangular fashion, is the ground. However, it and the post at the right (closest to passenger side) is hot when I put a test light on it. I first realized this when I was feeling around with the car running and got "buzzed". (Note to self: do not feel up under the dash when car is running).

I could not get to the left post but will try if it might make a difference. Does anyone know what else to try before I yank it and send it off for repair? Thanks in advance!

1968 SS 350 Camaro, 4-speed, California car, restoration complete. Brought back to life after almost 27 years of silence!

Built: 3rd week of July, 1968
Silenced: 12/12/1978
Resurrected: 05/01/2005
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post #2 of 14 (permalink) Old May 3rd, 05, 04:08 PM
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Jim
 
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Re: Tach woes

Try to find some posts I did on this this past winter. My new oer tictoc tach works good.

Since I was using aftermarket console gauges and keeping the idiot lights, rather than spend $300 on the factory guage harness and pcb, I modified the existing ones,

Did you gat the tach pcb, or work over the existing one?

If you can find my post on this, it for sure covers which connector is which on the new tach, but if u used the pcb, then the only left over connection would be the one that goes to the coil, which the factory ran independant of the rest of the harness.

You do have the tach wire on the neg side of the coil, right?





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post #3 of 14 (permalink) Old May 3rd, 05, 08:35 PM Thread Starter
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Kevin
 
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Re: Tach woes

Not to be too stupid but I am not sure what a pcb is. I did buy a new harness to include the tach and console guages. Also, the brown wire is connected to the neg. side on the coil.

1968 SS 350 Camaro, 4-speed, California car, restoration complete. Brought back to life after almost 27 years of silence!

Built: 3rd week of July, 1968
Silenced: 12/12/1978
Resurrected: 05/01/2005
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post #4 of 14 (permalink) Old May 3rd, 05, 08:42 PM
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Jim
 
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Re: Tach woes

pcb is the plastic thingy that runs the wires thru the dash carrier, the 68 is different with or without tach and guages.





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post #5 of 14 (permalink) Old May 8th, 05, 01:33 AM
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Re: Tach woes

You either need to get the correct printed circuit board ($70 from the restoration catalogs) or know how to wire it yourself.
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post #6 of 14 (permalink) Old May 8th, 05, 12:54 PM Thread Starter
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Kevin
 
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Re: Tach woes

I already bought the correct circuit board. As I stated above I also bought the harness for a tach and gauges. I was uncertain if there is a particular ground I am not getting as the assebly manual doesn't show anything. I shouldn't have to wire anything outside of that.

1968 SS 350 Camaro, 4-speed, California car, restoration complete. Brought back to life after almost 27 years of silence!

Built: 3rd week of July, 1968
Silenced: 12/12/1978
Resurrected: 05/01/2005
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post #7 of 14 (permalink) Old May 9th, 05, 08:14 AM Thread Starter
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Kevin
 
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Re: Tach woes

I thought I would post a follow-up. I removed the cluster yesterday and took a good look. I found that I did not have a ground on the cluster itself, as shown in the assembly manual.

The diagram did not show exactly where the ground went. I grounded it to a metal screw almost directly in the middle (favoring the tach side) of the gauges at the bottom. On the other end, I grounded it to a factory hole on the pedal assembly.

Needless to say this did not help the tach. My L and Right turn signal lights blink now so it wasn't a total waste of time.

Unless anyone else has an idea I guess I will yank it and send it off for repair.

I am just amazed. I was SURE this thing would work after buying it on EBAY.

1968 SS 350 Camaro, 4-speed, California car, restoration complete. Brought back to life after almost 27 years of silence!

Built: 3rd week of July, 1968
Silenced: 12/12/1978
Resurrected: 05/01/2005
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post #8 of 14 (permalink) Old May 11th, 05, 12:20 AM
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Re: Tach woes

Just on a whim I looked at the back of my '69 cluster. IN '69 the Tach has labeled 12V and COIL, and a third unlabled tab in the middle. '68 may be different, but my impression is this thing needs a (-) ground, 12 Vdc, and a signal from the coil. I hope this helps...

Rob

Robert

'69 X-33 since 1984

"Its all crazy..."
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post #9 of 14 (permalink) Old May 16th, 05, 08:40 PM
 
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Re: Tach woes

I am working on a 67 tach with MSD problems, I would in your position remove the tach and connect it to the car with jumper wires observing proper wiring, this should help you decide what to do next. If you have any type of electronic box, connect it to a stock set up.
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post #10 of 14 (permalink) Old May 16th, 05, 08:43 PM
 
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Re: Tach woes

any one out there used MSD with a factory 67 tach, I hear there is a special filter, still waiting for the part # from MSD?
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post #11 of 14 (permalink) Old May 19th, 05, 02:59 PM
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Jim
 
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Re: Tach woes

If using an MSD distributor with a stock tach it will work. Using an MSD distributor and or ignition box with an OE aftermarket or reworked tach, you will need a filter. Tach filters are available from MSD or you could make one. Do a search on tach filters and you should find something. You can also go to the MSD forum and ask their tech department for a filter. They will usually send you one free if you have a MSD distributor. http://www.msdignition.com/forums/in...load/index.php
You shouldn't get "BUZZED" from anything under the dash unless it's not wired correctly. I'll check my diagrams when I get home and see if I can help you out.
Jim
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post #12 of 14 (permalink) Old May 19th, 05, 03:13 PM Thread Starter
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Kevin
 
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Re: Tach woes

Thanks Jim - I certainly did get "BUZZED". Basically there are 3 small bolts on the back of the tach in a triangular fashion. The top one and the one to the right (passenger side) are both hot when I put a light on them.

1968 SS 350 Camaro, 4-speed, California car, restoration complete. Brought back to life after almost 27 years of silence!

Built: 3rd week of July, 1968
Silenced: 12/12/1978
Resurrected: 05/01/2005
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post #13 of 14 (permalink) Old May 20th, 05, 11:55 AM
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Jim
 
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Re: Tach woes

68SS

I'll need a little more time to find the diagram I'm looking for. Basically if you hook up the tach directly (without the harness) you can prove it's working properly. Next you would check the harness to see if it doing what it's supposed to electrically. There should be some type of marking on the back for power ( it may be IGN.), Ground (GND) and usually a dark brown wire to the negative side of the coil. (NEG). If the tach works but is erratic or doesn't read correctly, it might be because it's not an original tach. If not, you will need a filter. I'll keep looking for the diagram in the meantime.
Jim
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post #14 of 14 (permalink) Old May 20th, 05, 03:10 PM Thread Starter
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Kevin
 
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Posts: 342
Re: Tach woes

Thanks Jim - I am running a factory original tach. I figured the power wire was run through the harness for the tach. I did run a ground from the cluster to the pedal bracket but I did not get anything. But, it was hard to tell exactly where the ground wire is supposed to go. The assembly manual is vague.

1968 SS 350 Camaro, 4-speed, California car, restoration complete. Brought back to life after almost 27 years of silence!

Built: 3rd week of July, 1968
Silenced: 12/12/1978
Resurrected: 05/01/2005
68SSCamaroinKS is offline  
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