Tic toc tach Problem

[Moparjack 489]

Hi all , a friend of mine change on his 68 charger R/T all the wiring harness in his charger to new one from year one . Also he order from year one a Original Repro tic toc tach and replace it with the the installed tic toc .
After the connecting and replacing was done he start the car and make the first test , everything working well also the tic toc tach , but after 15 second’s the tic toc tach go to “zero “ no function in the tach anymore .... all other instruments working fine .
Any idea what can cause this problem ???
Thanks in advance ,
Steffen

 

[Demonic]

Ground is through the dash frame, Blue is switched power. Grey is the signal from the coil negative (- ) side. What sort of ignition system? Check for 12v with the key "on" on the blue wire, and the dash metal as ground.

 

[steve817]

The problem is that it's repop.

 

[Moparjack 489]

Ground is through the dash frame, Blue is switched power. Grey is the signal from the coil negative (- ) side. What sort of ignition system? Check for 12v with the key "on" on the blue wire, and the dash metal as ground.

Electronic with chrome box and firecore coil

 

[Moparjack 489]

The problem is that it's repop.

You mean is broken nearly out of the box ?

 

[Moparjack 489]

Ground is through the dash frame, Blue is switched power. Grey is the signal from the coil negative (- ) side. What sort of ignition system? Check for 12v with the key "on" on the blue wire, and the dash metal as ground.

Also 12V with key Ignition on is on the tach . Any other ideas what cause the problem ? It was working with engine running but just 15 seconds ...., after the tach goes to zero

 

[RJRENTON]

IMO...
The likely problem cause is the electronic ignition ECU and the coil. IF the coil's trigger pulses are too high (voltage wise), it is possible that the higher voltages to the tach input MAY have destroyed some components on the tach board, inside the "can" so to speak. As others mentioned, have you checked to insure that the tach is grounded? How about the gray wire going thru the bulk head connections to insure a good connection?
To be sure, you may need to remove the tach clock assembly, open it ip and inspect the internals for damage. Who did you purchase the tic toc tach from? Can you return it for inspection or replacement?
BOB RENTON

 

[Moparjack 489]

IMO...
The likely problem cause is the electronic ignition ECU and the coil. IF the coil's trigger pulses are too high (voltage wise), it is possible that the higher voltages to the tach input MAY have destroyed some components on the tach board, inside the "can" so to speak. As others mentioned, have you checked to insure that the tach is grounded? How about the gray wire going thru the bulk head connections to insure a good connection?
To be sure, you may need to remove the tach clock assembly, open it ip and inspect the internals for damage. Who did you purchase the tic toc tach from? Can you return it for inspection or replacement?
BOB RENTON

It’s from year one !
Thank you for the comments Bob, we will check it !