[Texas67sedan]

Hello guys. I've installed a new (repro) rally gauge kit and I've purchased a new dash harness correct for cars with gauges. I've called m&h and they only tell me that the light tan wire goes on the tach. Didn't say which side or what. Can't find any info on the interweb as well. I've got it connected this way now but the tach doesn't work but every time you cycle the switch the needle pegs out then back to zero. Didn't know if anyone knows what I'm doing wrong. Thanks.in advance.

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[abefromen]

The needle cycling every time the key is turned is normal with the repop rally gauge tachs.

Why it isnt working is another issue.

[Peter Serio]

According to your photo it look like you have it wired properly. The tab with the "+" symbol needs 12 volts + battery power whenever the key is in the on or run position and the Tab with the S is the wire that goes out underneath your hood to the "-" side of the coil. The is the wire that senses RPM so it is labeled "S" The metal housing needs a ground wire attached to it in order for the tach to get a good ground.


The tach goes thru a learning cycle every-time you start your engine. When you turn your car off these modern tachs do not return to zero as an original GM tachometer would. So when you start the modern tach needs to find it's zero point. Hence the start-up learning cycle, this is totally normal.

[Texas67sedan]

Originally Posted by Peter Serio

According to your photo it look like you have it wired properly. The tab with the "+" symbol needs 12 volts + battery power whenever the key is in the on or run position and the Tab with the S is the wire that goes out underneath your hood to the "-" side of the coil. The is the wire that senses RPM so it is labeled "S" The metal housing needs a ground wire attached to it in order for the tach to get a good ground.


The tach goes thru a learning cycle every-time you start your engine. When you turn your car off these modern tachs do not return to zero as an original GM tachometer would. So when you start the modern tach needs to find it's zero point. Hence the start-up learning cycle, this is totally normal.

Ok. So the tach read wire should be built into the engine harness? The only wire I see connected is the white and orange striped wire on the negative side. I'll ground the housing like you said. As well.

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[Old Goat 67]

Originally Posted by Texas67sedan

Ok. So the tach read wire should be built into the engine harness?

No, the tach wire is a completely separate wire from the coil through the firewall to the S terminal, with a 1 amp fuse holder built into it.

The Orange wire you have connected there is generally a 12v lead in the dash harness.

[Peter Serio]

On all 66 and 67 Rally gauge cars the tach sense wire was made in 2 separate sections. There is a dash portion which is wrapped into the tape in the main dash harness (tan wire). That wire breaks out just above the fuse block. Then there is an extension section that plugs into that and goes thru a rubber grommet in the firewall just beside the fuseblock. This wire follows the metal "J" hooks attached to your firewall and then attaches to the "-" terminal of your coil.

There is a one amp in-line glass fuse in a plastic holder just prior to the fork terminal end (right beside the coil). The dark brown wire you have attached to the "+" of your new tach needs to be fused. As you have it now your new tach is NOT protected. The tach needs a 1 or 1 & 1/2 amp fuse Maximum to protect your 12 volt "key on" power feed.

[Texas67sedan]

Guys thank you for your help. Got the harness from m&h and it works perfect.

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[vidguy]

In Texa67sedan's case, initially he must not have had the Tan wire connected at the other end to the coil "-" , since he did not have the extension harness at that point, right? I just want to understand the wiring of these repro tachs compared to the original. I have the M&H harness and extension and used them with my original tach/gauges for years. I should wire this one up the same way Texas67sedan has pictured it (if the Tan wire is connected to the coil "-". right?
Thanks!

[1971455HO]

Hello, I usually hang out in the 70-73 bird forums. Hope this isn't considered high-jacking anybodys thread. Not my intent. Just need some help. My friends 67 goat is going to paint pretty soon. I'm going to help him rewire it, install disc brakes and pretty much get it all back together when it gets back to his garage. He has bought all new harness's from American Wiring. He ordered it to be compatible using an HEI distributor. He's busy restoring his gauges right now. I need to know if we can simply pug his tach straight to the plug on the HEI unit? I'm a little afraid it might zap his tach since the HEI uses a full 12 volt. Any help is much appreciated.

thanks,
Eddie

[george kujanski]

Make sure the tach wire to the tach is plugged in to the HEI "tach" terminal and you will be good to go.

George

[1971455HO]

Originally Posted by george kujanski

Make sure the tach wire to the tach is plugged in to the HEI "tach" terminal and you will be good to go.

George

Got it...thanks a lot George. There are a dozen different answers out here on the web.

[vidguy]

I have this reproduction gauge set. I was trying to confirm that the way Texas67sedan pictured, with 12 volts to the red teminal and the tan wire to the "-" terminal on the coil, is the correct way to wire this new tach up too.
Thanks.