Autometer tach install probs

GhOsT6_9 · 03-15-2004, 05:50 PM

Alright I've just installed my new Autometer C2 tach, but whenever I bring the engine up to the shift point or beyond, the shift light comes on but flashes instead of holding steady.

Any idea what would cause this?? I've checked all my connections and my grounds are good.

I think that it may have been my coil connection. Just to double check, I know the negative wire is the one to connect to. I'm pretty sure that should be the "green" wire, am I correct or wrong on this assumption?? But for some reason I let my friend convince me to connect it to the red (probably + hot wire) and use that. I think that might be causing the shift light problems, by giving a bad signal.

84LX89GT · 03-15-2004, 06:52 PM

You want to hook up the green wire to the coil - side. The coil + side has a constant 12v until the negative side is grounded by the pcm. The negative side is an open circuit until it is grounded by the pcm. I've never hooked up a tach to the + side of the coil, but instead of just having a ground, you're connected to power and then it goes through the windings of the coil to ground. I imagine it may not hurt anything but try hooking it up to the - side of the coil.

GhOsT6_9 · 03-15-2004, 07:57 PM

Thats what I figured the problem was. Hooking to the + side doesn't seemed to have hurt anything, the tach works perfectly till the shiftlight comes on.

I'll re-wire it tonite or tomorrow. Thanks a bunch, hopefully that fixes the problem.

03-15-2004, 05:50 PM	#1
GhOsT6_9 Registered Member Join Date: May 2000 Location: Ontario,Canada Posts: 233	Autometer tach install probs Alright I've just installed my new Autometer C2 tach, but whenever I bring the engine up to the shift point or beyond, the shift light comes on but flashes instead of holding steady. Any idea what would cause this?? I've checked all my connections and my grounds are good. I think that it may have been my coil connection. Just to double check, I know the negative wire is the one to connect to. I'm pretty sure that should be the "green" wire, am I correct or wrong on this assumption?? But for some reason I let my friend convince me to connect it to the red (probably + hot wire) and use that. I think that might be causing the shift light problems, by giving a bad signal. __________________ 1989 Mustang LX Notch 5.0L, T-5, 1969 351W heads, cut & welded stock plenum, F-303 cam, Mac 1 5/8 full length headers, Cat'd H-pipe, 3.73 gears, Underdrives, SSM lift bars, E-Fan, 3G Alt, Custom Chip, Autometer gauges, Weld Draglite wheels , M/T ET Street Radials Best 1/4: 13.33@101.53MPH

03-15-2004, 06:52 PM	#2
84LX89GT Mustangs Join Date: Jul 2000 Posts: 1,938	You want to hook up the green wire to the coil - side. The coil + side has a constant 12v until the negative side is grounded by the pcm. The negative side is an open circuit until it is grounded by the pcm. I've never hooked up a tach to the + side of the coil, but instead of just having a ground, you're connected to power and then it goes through the windings of the coil to ground. I imagine it may not hurt anything but try hooking it up to the - side of the coil. __________________ 2005 Suzuki Hayabusa GSX1300-R 1980 Ford Thunderbird - 255 V8 ported heads, 5.0L ported stock headers, O.R. H-pipe and Flowmaster 2-chambers, dual roller timing chain hi-po Mack Truck hood emblem 1985 Mustang GT 5.0L T5, F-303, GT40p, headers, off-road h, flowmasters, MSD stuff, etc. Sold 02/06/04 1989 Mustang GT ET: 13.304@102.29 mph (5-24-03) Sold - 1998 Mustang Cobra coupe, 1/4 mile - street tires: 13.843@103.41 (bone stock)

03-15-2004, 07:57 PM	#3
GhOsT6_9 Registered Member Join Date: May 2000 Location: Ontario,Canada Posts: 233	Thats what I figured the problem was. Hooking to the + side doesn't seemed to have hurt anything, the tach works perfectly till the shiftlight comes on. I'll re-wire it tonite or tomorrow. Thanks a bunch, hopefully that fixes the problem. __________________ 1989 Mustang LX Notch 5.0L, T-5, 1969 351W heads, cut & welded stock plenum, F-303 cam, Mac 1 5/8 full length headers, Cat'd H-pipe, 3.73 gears, Underdrives, SSM lift bars, E-Fan, 3G Alt, Custom Chip, Autometer gauges, Weld Draglite wheels , M/T ET Street Radials Best 1/4: 13.33@101.53MPH

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