Smoking Tachometer
#1
10-23-2023, 03:25 PM
Smoking Tachometer
I installed a replacement tachometer in my 69. It worked fine for several years. Last start the smoke rolled from it! It no longer works. Why?
Did the voltage regulator go over voltage?
Is there a ground issue?
Petronix Ignitor II ?
Hotter coil ?
I’m going to buy a new tach and install a tach filter this time.
Anyone else with info appreciated!
Does anyone fix smoked tachs ?
Thanks
Did the voltage regulator go over voltage?
Is there a ground issue?
Petronix Ignitor II ?
Hotter coil ?
I’m going to buy a new tach and install a tach filter this time.
Anyone else with info appreciated!
Does anyone fix smoked tachs ?
Thanks
#3
10-24-2023, 06:32 AM
What SoCal67 said. There is high voltage and there is dirty voltage. Running too high a voltage over time can fry anything.
Keep in mind that on these older cars the voltage is not very clean to start with, an AC compressor clutch disengaging can shoot a quick 100 volts spike into your electrical system. The only reason I mentioned the AC is because any electrical product sold to wire into these cars need to be robust enough to handle dirty voltage. I would probably verify the resistance in the wire between the tack and the ground just to be sure. The only thing I can think of is enough resistance in the ground could increase the voltage need to make the tach work. You could try to give the tack manufacture a call and see if the have any specs you should check for before installing a new one. Tach smoking is not a common issue I am aware of. Maybe the manufacture will have more insight. The last thing they want is for you to install another and fry it cause new one will be warranty. If there is an issue I would guess it would be due to power ground supply to the tach not to the lead going to the coil.
My 67 has the original tack with the petronix ignitor and coil. Before that it had an accel coil. Since the tack is just reading a pulse and counting an increase of primary voltage draw should not have an effect. Mine did fry the power in circuit on mapping on the back of the cluster without hurting the tach. Its like a dwell meter. It can measure the pulse on the smallest fuel injector or a 100,000 volt coil.
Keep in mind that on these older cars the voltage is not very clean to start with, an AC compressor clutch disengaging can shoot a quick 100 volts spike into your electrical system. The only reason I mentioned the AC is because any electrical product sold to wire into these cars need to be robust enough to handle dirty voltage. I would probably verify the resistance in the wire between the tack and the ground just to be sure. The only thing I can think of is enough resistance in the ground could increase the voltage need to make the tach work. You could try to give the tack manufacture a call and see if the have any specs you should check for before installing a new one. Tach smoking is not a common issue I am aware of. Maybe the manufacture will have more insight. The last thing they want is for you to install another and fry it cause new one will be warranty. If there is an issue I would guess it would be due to power ground supply to the tach not to the lead going to the coil.
My 67 has the original tack with the petronix ignitor and coil. Before that it had an accel coil. Since the tack is just reading a pulse and counting an increase of primary voltage draw should not have an effect. Mine did fry the power in circuit on mapping on the back of the cluster without hurting the tach. Its like a dwell meter. It can measure the pulse on the smallest fuel injector or a 100,000 volt coil.
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