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Old 07-14-2004, 08:28 PM
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Arrow mustang tach wiring

Hi there, I'm a new guy on the board here. My name is Steve Gortsema and my project is an 89 Mustang GT. I also have a 92 LX 5.0 that I am using as a donor. My problem is that I'm trying to get a factory tach to work in the car and I seemed to have gotten in over my head. Here's the background . . .

When I purchased the car the factory tach was not working and it had a large AutoMeter tach installed on top of the dash which did work. I want to go to more of a factory look on the interior so I removed the aftermarket tach. I tried running a wire from the ignition coil to the tach signal wire going into the cluster. The tach still didn't work so I figured it was a bad tach.

The tach in my '92 Mustang worked fine and the cluster was in better shape so I decided to swap clusters. Unfortunately the cluster circuits are different between '89 and '92 so I had to rewire the connectors that go into the back of the cluster. I first did this on the '92 car to accept the '89 tach to test out my deciphering of the wiring changes. This seemed to work alright - everything except the tach works now on the '92 car (no different from when the '89 cluster was on the '89 car).

OK, next step was to rewire the connectors on the '89 car to accept the '92 cluster. However, when I tried it out, the tach doesn't work now. Here's the way I rescrambled the wires:

Horizontal Connector:
Connector Terminal/Wire(old connector terminal location)
1/x(not used)
2/5 of other connector
12/13 of other connector
14/6 of other connector

Vertical Connector:
Connector Terminal/Wire(old connector terminal location)

6/2 of other connector
13/14 of other connector

If anyone sees any errors with my rewiring, please point them out.

The next thing I tried was to hook up the tach circuit directly to the appropriate signals on the 89 car to see if I could get it to work that way (remember this tach worked fine in the 92 car). I connected the positive battery post to terminal location 4 on the vertical receptacle in the back of the cluster (passenger's side). I connected a ground wire to terminal location 9 on the horizontal receptacle in the cluster. Then I connected a wire from the coil (Dark Green/Yellow wire) to terminal location 11 on the vertical receptacle in the cluster. I tested it out this way and the tach still didn't work.

I don't know if it makes any difference, but the car has an MSD Blaster TFI coil. The AutoMeter tach was connected to the same DG/Y wire on the coil and worked fine though.

Any guiddance on how to fix this (besides buying a new 89 cluster and rewiring it back the way it started) would be much appreciated.

Thank you for hanging in there with this long note!

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