Tachometer dead
Former Vendor
Joined: Aug 2006
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The power wire on the 75-77 tach is the highest terminal, the signal is the lowest.
How do you test for signal.. you could use an aftermarket tach, we use a scope. You might test the wire for continuity from the tach to the filter connection to make sure the wire isn't broken... easy to do with a ohms meter.
Willcox
Former Vendor
Joined: Aug 2006
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Willcox
Melting Slicks
Joined: Mar 2007
Posts: 2,520
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From: Hinckley OH
You need a diagnostic tachometer. Most old school mechanics should have one. I don't know if a parts store would have one that they could hook up. All they would do is attach a lead to the tach terminal on the distributor cap and the other to a ground and start the engine. If the diagnostic tach doesn't show the RPM's then the problem is in the connection to the coil inside the distributor cap.
Race Director
Joined: Sep 1999
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From: Plano TX
Some easy diagnostics when the tach doesn't move with engine rpm:
Turn ignition on. Does the needle move to zero?
No: Bad movement or tach board, or no power to tach/ground to tach.
Yes: Bad tach board or signal wire to ignition coil or tach filter.
Turn ignition on. Does the needle move to zero?
No: Bad movement or tach board, or no power to tach/ground to tach.
Yes: Bad tach board or signal wire to ignition coil or tach filter.
Thread Starter
Instructor
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From: Hudson valley Ny
You do that before you pull the column... but if it is out, you can plug it back up for testing.
The power wire on the 75-77 tach is the highest terminal, the signal is the lowest.
How do you test for signal.. you could use an aftermarket tach, we use a scope. You might test the wire for continuity from the tach to the filter connection to make sure the wire isn't broken... easy to do with a ohms meter.
Willcox
Former Vendor
Joined: Aug 2006
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
There is a three wire connector on the back of the tach (shown below).
One wire is power, one is ground and one is signal. Pull the connector off the back of the tach, test the pink wire for power with the key on... using a ground like the door jamb switch or something else... If you have power, then switch the ground to the black wire on the connector and test for power again.. if you have power again then you have verified A) power and fuse are good, B) the ground is good. Then test the brown wire from the connector to the plug by the distributor for continuity. Do not test with the filter installed. Test where the filter plugs in... If you have continuity... then your back to my last post.. (only thing it can be is a signal issue, a board issue or a movement issue.
All of this is outlined in the help page I posted you the link to above. (only it's for a 78-82 style being used).
One wire is power, one is ground and one is signal. Pull the connector off the back of the tach, test the pink wire for power with the key on... using a ground like the door jamb switch or something else... If you have power, then switch the ground to the black wire on the connector and test for power again.. if you have power again then you have verified A) power and fuse are good, B) the ground is good. Then test the brown wire from the connector to the plug by the distributor for continuity. Do not test with the filter installed. Test where the filter plugs in... If you have continuity... then your back to my last post.. (only thing it can be is a signal issue, a board issue or a movement issue.
All of this is outlined in the help page I posted you the link to above. (only it's for a 78-82 style being used).
Thread Starter
Instructor
Joined: Jan 2014
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From: Hudson valley Ny
There is a three wire connector on the back of the tach (shown below).
One wire is power, one is ground and one is signal. Pull the connector off the back of the tach, test the pink wire for power with the key on... using a ground like the door jamb switch or something else... If you have power, then switch the ground to the black wire on the connector and test for power again.. if you have power again then you have verified A) power and fuse are good, B) the ground is good. Then test the brown wire from the connector to the plug by the distributor for continuity. Do not test with the filter installed. Test where the filter plugs in... If you have continuity... then your back to my last post.. (only thing it can be is a signal issue, a board issue or a movement issue.
All of this is outlined in the help page I posted you the link to above. (only it's for a 78-82 style being used).
One wire is power, one is ground and one is signal. Pull the connector off the back of the tach, test the pink wire for power with the key on... using a ground like the door jamb switch or something else... If you have power, then switch the ground to the black wire on the connector and test for power again.. if you have power again then you have verified A) power and fuse are good, B) the ground is good. Then test the brown wire from the connector to the plug by the distributor for continuity. Do not test with the filter installed. Test where the filter plugs in... If you have continuity... then your back to my last post.. (only thing it can be is a signal issue, a board issue or a movement issue.
All of this is outlined in the help page I posted you the link to above. (only it's for a 78-82 style being used).
So I can get to that plug without taking car apart
Will I be able to reach behind dash and unplug it with car together and will it have enough slack to pull it down to test it ?guess I should of done this before ordering the board thanks John
Former Vendor
Joined: Aug 2006
Posts: 76,656
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Yes.. you can reach it without pulling the dash.. you'd better get your upside down hat on though.
You test it today.. post again if you don't need the board and I will stop it tomorrow
Willcox
You test it today.. post again if you don't need the board and I will stop it tomorrow
Willcox
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Thread Starter
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From: Hudson valley Ny
I will try and do some testing when I start taking it apart thanks
Thread Starter
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From: Hudson valley Ny
Thread Starter
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From: Hudson valley Ny
What would be great is some direction on how to hook it up after I put the board in and the column is still out so I can test it before I put it together thanks
Thread Starter
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From: Hudson valley Ny
Just one more thing to check before you tear into the dashboard. Make sure you have a tach signal from the distributor. The tach on my '76 doesn't work but neither does my hand held diagnostic tach if I hook it up. The hand held tach works on my '74 and my Jeep so I think the problem is in my coil connection inside the distributor cap. I just haven't bothered to take it apart yet.
I borrowed a old what is called a maxi tune connected to distributor where tach comes out and didn't get a reading I think I did it right
I chose the 4/8 cylinder selection on it and also the lo rpm setting
I also connected it to battery and saw the needle move so it works?
If I did it right what is this problem maybe a new cap? Who knows at this point
Thanks John
Former Vendor
Joined: Aug 2006
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Make some jumper wires and run power to the one marked positive, run a ground to the ground. Then run a jumper from the signal terminal to the distributor connection... If all is right, the tach should work.
If you go to the video.. at the 3.14 mark you'll see me doing this too.
Melting Slicks
Joined: Mar 2007
Posts: 2,520
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From: Hinckley OH
Hey there
I borrowed a old what is called a maxi tune connected to distributor where tach comes out and didn't get a reading I think I did it right
I chose the 4/8 cylinder selection on it and also the lo rpm setting
I also connected it to battery and saw the needle move so it works?
If I did it right what is this problem maybe a new cap? Who knows at this point
Thanks John
I borrowed a old what is called a maxi tune connected to distributor where tach comes out and didn't get a reading I think I did it right
I chose the 4/8 cylinder selection on it and also the lo rpm setting
I also connected it to battery and saw the needle move so it works?
If I did it right what is this problem maybe a new cap? Who knows at this point
Thanks John
It would be nice if you had another vehicle to test the meter on to make absolutely certain that it works.
Thread Starter
Instructor
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From: Hudson valley Ny
There are two clips which hold the loom that holds the tops of the spark plug wires on the top of the distributor. Unclip those and pull off the loom and wires. Beneath that are two screws that hold the coil cover onto the distributor cap. Remove them and lift the cover off. You should see the wires and contacts that go to where the wires for the power and tach wires hook into the distributor. About all you can do is make sure those wires are intact and still connected to the coil.
It would be nice if you had another vehicle to test the meter on to make absolutely certain that it works.
Melting Slicks
Joined: Mar 2007
Posts: 2,520
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From: Hinckley OH
I can't speak for that meter but mine worked on my '99 Jeep which doesn't have points.
It might be worth your time to just take a look at the wires to the coil because that's a lot easier than tearing into the dash. I have seen a few posts on the forum where that was the problem.
It might be worth your time to just take a look at the wires to the coil because that's a lot easier than tearing into the dash. I have seen a few posts on the forum where that was the problem.
Last edited by my 76 ray; Apr 2, 2014 at 10:12 AM.
Thread Starter
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From: Hudson valley Ny
I can't speak for that meter but mine worked on my '99 Jeep which doesn't have points.
It might be worth your time to just take a look at the wires to the coil because that's a lot easier than tearing into the dash. I have seen a few posts on the forum where that was the problem.
It might be worth your time to just take a look at the wires to the coil because that's a lot easier than tearing into the dash. I have seen a few posts on the forum where that was the problem.
Thanks so much for helping
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From: Hudson valley Ny
Thread Starter
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From: Hudson valley Ny
12 volts with key on and engine off
And 19 or so at idle with an increase to 22 ish when u throttle it still waiting to see if someone will lend me a tach but I'm thinking this test may be showing its sending a signal?
Thread Starter
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From: Hudson valley Ny
I could get a voltage reading from an amp meter off the tach side of the distributor but that's not the right way to do it but wouldn't that be a plus that maybe it's giving a signal
I will try another tach
It doesn't matter that I'm powering it with a different battery that's out of the car?