Checked Tach With Multi Meter

91cobra5.0 · April 6th, 2008, 12:47 PM

12 volts from battery
11 volts from coil
good ground

you guys think the tach went bad?

fogged306 · April 6th, 2008, 12:50 PM

when the car is running the coil wire should be in A/C voltage, not D/C. I think you have the wrong coil wire going in to the tach. Thats the input to tell it how fast the engine is spinning. It creates an A/C voltage that goes up with RPM.

91cobra5.0 · April 6th, 2008, 03:32 PM

ok ill just stick it into the other wire just to see what it does

fogged306 · April 6th, 2008, 03:44 PM

You want to ground the black lead and use the red lead to test whichever wire you think is your tach signal wire coming off the coil. Like I said before its A/C so make sure you set the DMM to A/C voltage. The right wire will go up in voltage with RPM's. It was dk. green/yellow on the stock coil, but I remember you saying you had an aftermarket.

91cobra5.0 · April 6th, 2008, 03:52 PM

well how bout this? can i just cut the wire that runs for the stock tach? and use it on the aftermarket?

fogged306 · April 6th, 2008, 04:12 PM

Does your stock tach work right now? if so, then yes, but I would tap into it rather than cut it.

April 6th, 2008, 12:47 PM	#1
91cobra5.0 Hardcore Enthusiast 91 mustang Unknown with new heads Join Date: Jan 2008 Location: colorado springs Posts: 1,579	Checked Tach With Multi Meter 12 volts from battery 11 volts from coil good ground you guys think the tach went bad? __________________ Fender well cold air intake, 3:73's, eibach springs, 65mm TB, electric fans, 3g upgrade, smog delete, advanced timing, MSD cap and rotor, ford racing 9mm plug wires, 75mm Pro-M MAF, flowmaster sieres 40 delta flows, gt-40 heads

April 6th, 2008, 03:32 PM	#3
91cobra5.0 Hardcore Enthusiast 91 mustang Unknown with new heads Join Date: Jan 2008 Location: colorado springs Posts: 1,579	ok ill just stick it into the other wire just to see what it does __________________ Fender well cold air intake, 3:73's, eibach springs, 65mm TB, electric fans, 3g upgrade, smog delete, advanced timing, MSD cap and rotor, ford racing 9mm plug wires, 75mm Pro-M MAF, flowmaster sieres 40 delta flows, gt-40 heads

April 6th, 2008, 03:52 PM	#5
91cobra5.0 Hardcore Enthusiast 91 mustang Unknown with new heads Join Date: Jan 2008 Location: colorado springs Posts: 1,579	well how bout this? can i just cut the wire that runs for the stock tach? and use it on the aftermarket? __________________ Fender well cold air intake, 3:73's, eibach springs, 65mm TB, electric fans, 3g upgrade, smog delete, advanced timing, MSD cap and rotor, ford racing 9mm plug wires, 75mm Pro-M MAF, flowmaster sieres 40 delta flows, gt-40 heads

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April 6th, 2008, 12:50 PM	#2
fogged306 Hardcore Enthusiast 89 GT Join Date: Apr 2007 Location: Happy? Posts: 1,304	when the car is running the coil wire should be in A/C voltage, not D/C. I think you have the wrong coil wire going in to the tach. Thats the input to tell it how fast the engine is spinning. It creates an A/C voltage that goes up with RPM.

April 6th, 2008, 03:44 PM	#4
fogged306 Hardcore Enthusiast 89 GT Join Date: Apr 2007 Location: Happy? Posts: 1,304	You want to ground the black lead and use the red lead to test whichever wire you think is your tach signal wire coming off the coil. Like I said before its A/C so make sure you set the DMM to A/C voltage. The right wire will go up in voltage with RPM's. It was dk. green/yellow on the stock coil, but I remember you saying you had an aftermarket.

April 6th, 2008, 04:12 PM	#6
fogged306 Hardcore Enthusiast 89 GT Join Date: Apr 2007 Location: Happy? Posts: 1,304	Does your stock tach work right now? if so, then yes, but I would tap into it rather than cut it.

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