Converted Electronic Tach
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 779
Likes: 1
From: Minneapolis MN
Converted Electronic Tach
When I had my '68 restorodded I had the shop send out the tach to be converted to electronic. Now I'm not sure where they sent it but I assume Tachman or Corvette Clocks.
My ignition is driven my a MSD 6AL box.
As they hooked it up, black to ground, green to coil negative, and red to coil positive it didn't work. I assume this is because of the nature of the MSD/CDI.
I've tried every combination of the tach output from the MSD box to the green or red wire of the tach to no avail. At this point I think I either need a MSD tach converter, or something is fried inside the tach because of how it was initially hooked up.
Can anyone shed light on this? I've got a black, green, and red wire...
My ignition is driven my a MSD 6AL box.
As they hooked it up, black to ground, green to coil negative, and red to coil positive it didn't work. I assume this is because of the nature of the MSD/CDI.
I've tried every combination of the tach output from the MSD box to the green or red wire of the tach to no avail. At this point I think I either need a MSD tach converter, or something is fried inside the tach because of how it was initially hooked up.
Can anyone shed light on this? I've got a black, green, and red wire...
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
I am kind of going through this same thing right now. Here is my take on the tach, if you are using the stock style electronic guts. On the positive lug of the tach, it is a switched 12v connection. The negative lug should be to ground. The tach lug should be to your signal. Here is a picture of the way it should be connected.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
When I had mine converted I used the green wire (tach lead) from the CD ignition box. The positive as said above is a 12 volt ignition source and ground. I even Td off another wire from the green wire and hooked it to my shift light. They all worked fine that way.
Melting Slicks
Joined: May 2002
Posts: 2,431
Likes: 52
From: Florida
Don't some boxes require the use of an amplifier?
"If you are triggering an MSD Blaster, 5,6, or 7 Series Ignition with its white wire or points terminal, you will need this Tach Adpater. This unit will correct the operation of most voltage triggered tachometers or fuel injection systems that do not work directly off the tach output terminal of the MSD Ignition Unit."
MSD #121-8910
"If you are triggering an MSD Blaster, 5,6, or 7 Series Ignition with its white wire or points terminal, you will need this Tach Adpater. This unit will correct the operation of most voltage triggered tachometers or fuel injection systems that do not work directly off the tach output terminal of the MSD Ignition Unit."
MSD #121-8910
Last edited by jimvette999; Apr 16, 2009 at 12:06 PM.
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 779
Likes: 1
From: Minneapolis MN
"If you are triggering an MSD Blaster, 5,6, or 7 Series Ignition with its white wire or points terminal, you will need this Tach Adpater. This unit will correct the operation of most voltage triggered tachometers or fuel injection systems that do not work directly off the tach output terminal of the MSD Ignition Unit."
Where did this quote come from? This is exactly what I'm doing, triggering my 6AL via the white fire from my Megasquirt.
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 779
Likes: 1
From: Minneapolis MN
Does anyone recognize this module?
I've tried straight from the MSD tach out, I've tried the tach wire feeding the ECU with the MSD 8910 tach adapter, and I've tried the tach wire without the 8910 all with no luck.
I've tried straight from the MSD tach out, I've tried the tach wire feeding the ECU with the MSD 8910 tach adapter, and I've tried the tach wire without the 8910 all with no luck.
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Melting Slicks
Joined: Mar 1999
Posts: 3,029
Likes: 137
From: Nashville TN area
did you ever hook your red wire up to switched 12vdc? you originally said it was going to the coil + wire.. hook it to a constant 12vdc supply that switches on and off with your key switch. black to any good chassis ground and then green to the signal wire.
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 779
Likes: 1
From: Minneapolis MN
G - Black
I - Red
S - Green
So obviously black and red are power and ground and green is signal but I don't understand what type of signal this module is expecting.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
When I had my '68 restorodded I had the shop send out the tach to be converted to electronic. Now I'm not sure where they sent it but I assume Tachman or Corvette Clocks.
My ignition is driven my a MSD 6AL box.
As they hooked it up, black to ground, green to coil negative, and red to coil positive it didn't work. I assume this is because of the nature of the MSD/CDI.
I've tried every combination of the tach output from the MSD box to the green or red wire of the tach to no avail. At this point I think I either need a MSD tach converter, or something is fried inside the tach because of how it was initially hooked up.
My ignition is driven my a MSD 6AL box.
As they hooked it up, black to ground, green to coil negative, and red to coil positive it didn't work. I assume this is because of the nature of the MSD/CDI.
I've tried every combination of the tach output from the MSD box to the green or red wire of the tach to no avail. At this point I think I either need a MSD tach converter, or something is fried inside the tach because of how it was initially hooked up.
Melting Slicks
Joined: Feb 2006
Posts: 2,092
Likes: 5
From: Fayetteville Arkansas
does the tach work at all? Did it ever work? What is it doing now if anything. I'm in the middle of upgrading my 72 with a elect tach out of a 75 and as I understand it you should be able to test the tach by disconnecting the green wire and then connecting the pos and negative and the tach should jump and then zero out. Have you tried that and seen what the tach does?
Sully
Sully
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 779
Likes: 1
From: Minneapolis MN
does the tach work at all? Did it ever work? What is it doing now if anything. I'm in the middle of upgrading my 72 with a elect tach out of a 75 and as I understand it you should be able to test the tach by disconnecting the green wire and then connecting the pos and negative and the tach should jump and then zero out. Have you tried that and seen what the tach does?