Tach Signal Wire
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Freshman User
Joined: Jun 2012
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Tach Signal Wire
I bought my truck and the wiring was cobbled together. I installed an HEI distributor and pulled out the duraspark setup including the brain box. I think the tach signal wire went through the box.
If so, what plug does it come off and what color is it?
Thanks
Ryan
If so, what plug does it come off and what color is it?
Thanks
Ryan
Thread Starter
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Freshman User
Joined: Jun 2012
Posts: 39
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Got the HEI installed and it is night and day difference. I still cant find the tach wire. I traced it back to where i thought it was, but it kills the truck when i run it to the coil. So now im not sure what to do. I guess all i can do is pull the cluster and try to do a continuity check on the wire going to the cluster. Anybody else have any suggestions?
Posting Guru
Joined: Jan 2002
Posts: 1,346
Likes: 8
From: Baltimore
This info is from a 88 service manual. 88 and 87 used the same dash
cluster.
I'm not sure if the 88 7.5L engine was Duraspark or TFI but this
is what the manual shows for the 7.5L tach wiring.
From the tach gauge a Dark Green/Yellow wire goes to the firewall
to connector C100. The wire pass into the engine compartment
to Connector C176 which is a Black colored 8 pin connector
located on the LH fender apron. The Dark Green/Yellow wire then
connects to a 1.8K ohm resistor. The other end of the 1.8k ohm
resistor then connects to the negative terminal of the coil.
In the 88 service manual they show the Duraspark ignition
used a Green wire from the negative terminal of the coil to the
Duraspark control module.
I suspect on your vehicle there must have been another wire that
was also attached to the negative terminal of the coil that went
to the 1.8k ohm resistor then thru the firewall connector and
to the dash cluster tach.
cluster.
I'm not sure if the 88 7.5L engine was Duraspark or TFI but this
is what the manual shows for the 7.5L tach wiring.
From the tach gauge a Dark Green/Yellow wire goes to the firewall
to connector C100. The wire pass into the engine compartment
to Connector C176 which is a Black colored 8 pin connector
located on the LH fender apron. The Dark Green/Yellow wire then
connects to a 1.8K ohm resistor. The other end of the 1.8k ohm
resistor then connects to the negative terminal of the coil.
In the 88 service manual they show the Duraspark ignition
used a Green wire from the negative terminal of the coil to the
Duraspark control module.
I suspect on your vehicle there must have been another wire that
was also attached to the negative terminal of the coil that went
to the 1.8k ohm resistor then thru the firewall connector and
to the dash cluster tach.
Posting Guru
Joined: Jan 2002
Posts: 1,346
Likes: 8
From: Baltimore
The bottom line is there must be a connection from the
wire that goes into the body harness (which appears
is the wire that goes to the tach) to the negative terminal
of the coil.
The diagram I looked at shows the Duraspark control module
has twoconnectors.
Two pin connector. White wire and a Red wire went
to the ignition switch.
Four plug connector.
Shows one Green wire to negative coil terminal. (Control module
grounds this wire to pulse primary of the ignition coil and also
this wire is used for the Tach signal.
Orange and a Purple wire to Stator.
Black wire Ground.
Here's the wiring for a EEC/TFI system
wire that goes into the body harness (which appears
is the wire that goes to the tach) to the negative terminal
of the coil.
The diagram I looked at shows the Duraspark control module
has twoconnectors.
Two pin connector. White wire and a Red wire went
to the ignition switch.
Four plug connector.
Shows one Green wire to negative coil terminal. (Control module
grounds this wire to pulse primary of the ignition coil and also
this wire is used for the Tach signal.
Orange and a Purple wire to Stator.
Black wire Ground.
Here's the wiring for a EEC/TFI system
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