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post #1 of 13 Old 08-03-2019, 09:34 PM Thread Starter
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Tach Messed Up

The tach on my 83 just started this today. It won't go higher than 2300, or below 15, even when the key is turned off. Anybody experience this before?
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post #2 of 13 Old 08-05-2019, 10:33 AM
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Re: Tach Messed Up

83 What?
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post #3 of 13 Old 08-05-2019, 10:46 AM
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Re: Tach Messed Up

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83 What?
Believe it's a Shelby Charger with carb...
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post #4 of 13 Old 08-05-2019, 10:59 AM
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Re: Tach Messed Up

I do not know what type of circuit board is used on an 83, however, the problems in the newer TD's is usually related to cracked solder joints on the PCB or a connection issue with the tach drive module to PCB or Tach to PCB.

The best I can tell from my wiring is the tach signal comes directly from the - coil to the cluster, what that voltage should be???
On the newer TD's the tach voltage is 2.4 AC volts but comes from the engine controller.

Maybe John can check his 83 FSM's to see if there are tach diagnostics in there.

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post #5 of 13 Old 08-05-2019, 11:49 AM
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Re: Tach Messed Up

The '83 FSM doesn't have any diagnostics for the Tach, only the removal & installation procedures.

The tach is not connected to the instrument circuit board but rather has its own 3 way connector.

"H4" in the Tach diagram is the common ground.
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post #6 of 13 Old 08-05-2019, 12:44 PM Thread Starter
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Re: Tach Messed Up

It's an 83 Shelby Charger. John is correct about the service manual. I was just wondering if anybody has run into this before. I don't think it's electrical cause it is showing 1300 without a key even in the car.
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post #7 of 13 Old 08-05-2019, 12:55 PM
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Re: Tach Messed Up

Could be the tach itself.
Remove it and try using a can of compressed air to gentle clean it. Hopefully some dust is making it stick.
Per parts manual part number is 5209682.

Didn't you get a new cluster? Maybe your old one still works???

Don't know if the ignition switch is causing an issue?

Try testing the 3 way connector with a voltmeter.
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post #8 of 13 Old 08-06-2019, 08:58 AM
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Re: Tach Messed Up

I have had tach issues with my car on a few occasions in the 29 years I have owned her.

It is common for the tach's to read funny or stop working if they get hit with an electrical spike, what if anything was done to this car before the tach started to act up?

If you remove the tach from the cluster and disconnect its electrical supply does the needle still stay at 1300?
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post #9 of 13 Old 08-06-2019, 09:46 AM Thread Starter
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Re: Tach Messed Up

I'll ck it when I get some more mobility, I can barely drive it right now. I was just wondering if this is a common problem. John, yes I have a whole cluster from a newer car, but it would take some work to make it work cause it has separate oil pressure and water temp gauges.
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post #10 of 13 Old 08-06-2019, 11:13 PM Thread Starter
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Re: Tach Messed Up

By the way what is the body designation for a Shelby Charger? Are they L bodies?
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post #11 of 13 Old 08-07-2019, 08:20 AM
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Re: Tach Messed Up

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Originally Posted by 71hemibird View Post
By the way what is the body designation for a Shelby Charger? Are they L bodies?
Yes any Omni/Horizon/Charger/Turismo/TC3/O24/Rampage/Scamp or the Shelby variants of, is an L-body

Tachs are EXTREMELY common to go to shit for the L-body clusters. Best bet is to disassembly, the tach portion can be removed, and clean the circuitry, reflow the solder joints and give it a try. If still nothing reasonable, it could then be wiring issue, tach driver (circuitry) has failed
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post #12 of 13 Old 08-07-2019, 10:26 AM Thread Starter
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Re: Tach Messed Up

Ok, I'll try that when I can move better, had knee replaced
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post #13 of 13 Old 08-08-2019, 11:06 AM
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Re: Tach Messed Up

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Ok, I'll try that when I can move better, had knee replaced
Ooooh!!!

Take care of yourself, the car will still be there.

Best Wishes For a Speedy Recovery!!!
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