Smoked my tach

[Logger10]

Hello folks,

I have a 72 340 Challenger Rallye, it has the stock electronic ignition, brand new wiring harness and it has a Holley Sniper EFI. It had a brand new OER Rallye Tach in the instrument cluster and it burnt up my first time out with the car. I pulled the cluster and it is not the wiring anywhere. As far as I can see there is no tach filter installed anywhere. Would it need one if there wasn't one there before, is it the lack of one that caused the new OER tach to fail? Any info gratefully appreciated. Thank you!

 

[Challenger RTA]

Are the turn signals working? How about the other gauges?

 

[Logger10]

Signals are good as well as other guages.

 

[Challenger RTA]

The reason I ask is the the tac is powered through the turn signal connection . The other gauges have there own voltage limiter. So my thoughts: alternator or regulator going bad? Can send wrong power to tac and cause the problem. Also clean grounds on regulator and alternator. The bolt and holes. Not a good enough ground. Path of lest resistance, the tac. The other Coil shorting out?

 

[Logger10]

The reason I ask is the the tac is powered through the turn signal connection . The other gauges have there own voltage limiter. So my thoughts: alternator or regulator going bad? Can send wrong power to tac and cause the problem. Also clean grounds on regulator and alternator. The bolt and holes. Not a good enough ground. Path of lest resistance, the tac. The other Coil shorting out?

Checked my wiring diagram and you are correct, the power for the tach comes from the Direction Flasher (blue wire). You may be on to something here, my instrument lights do not work either, the other side of the flasher (black wire) runs to the radio connector. The red power wire from the fuse box connects here to the radio connector then the panel lights are fed (orange wires) When I'm not still bitter after smoking a $400.00 tach I will look into it! Thank you!

 

[Challenger RTA]

Instrument lights do not work either

That might be a ground too. As I said about the above. I'm thinking it's a bad grounds. Electricity takes the path of lest resistance, and I think you tac was it and completed the path. Power surge? I would also consider that ALT and or voltage reg might be bad or going bad. Wrong voltage. Clean mounting bolts on dash frame they are the ground for other things in the dash. The cluster gauges and lights are grounded to the dash by the mounting screws. Here again clean other grounds. Chassis ground in front of the battery, motor ground bolt and thread, Alternator mounting bolts and thread. Also voltage regulator and ECM ground. And of course the battery terminals, bulk head connecters.

I just cleaned and checked my bulkhead connectors. Low and behold the car would not start after. It would start in the start position then die. Out came out the test light. No power at the resistor blue wire and engine side bulkhead. So under the dash I go. check column plug had power. So pop of the fuse box and found the DB wire was push inside. Fiddled with it to get it to stay in place. Voila! Check the brown wire while I was the and a few others.