Tach maxed out at idle
#1
Tach maxed out at idle
I started this thread in the interior section
https://www.thirdgen.org/forums/inte...em-gauges.html
Maybe I should have started here instead.
At this point I'm trying to find info on how much voltage I should see on the dash connector for the Tach? White wire coming from the coil.
With the engine idling, I'm measuring 13.5vdc. My tach sits at 7000 rpm.
Anyone have any info on what I should be reading?
https://www.thirdgen.org/forums/inte...em-gauges.html
Maybe I should have started here instead.
At this point I'm trying to find info on how much voltage I should see on the dash connector for the Tach? White wire coming from the coil.
With the engine idling, I'm measuring 13.5vdc. My tach sits at 7000 rpm.
Anyone have any info on what I should be reading?
#2
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Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
Re: Tach maxed out at idle
Should be batt, with about a 3 millisecond pulse to ground for every cyl firing. Which wouldn't show up on a DC meter at idle. So what you're seeing is probably right.
Sounds like your tach is busticated, same as everybody else's.
Read a few posts on this forum about "tach" and see what you think.
Sounds like your tach is busticated, same as everybody else's.
Read a few posts on this forum about "tach" and see what you think.
#4
Re: Tach maxed out at idle
So I came across this thread
https://www.thirdgen.org/forums/elec...-required.html
What is the open 4 - 10 that its referring too?
I haven't seen that in another thread yet
https://www.thirdgen.org/forums/elec...-required.html
What is the open 4 - 10 that its referring too?
I haven't seen that in another thread yet
#5
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Car: Yes
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Re: Tach maxed out at idle
He had the schematic for 2 things conflated... the LM1819 chip, and the factory's resistor array. It is of no consequence.
#7
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Re: Tach maxed out at idle
does the tach return to minimum when ignition switched off?-IIRC '82-89 tachs can get "stuck"at upper RPM section of dial if power is cut while tach is reading high RPM-as I recall,high revs can correct this condition.
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#8
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Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
Re: Tach maxed out at idle
It's not a question of "no one has figured it out"; it's just electronics after all, and just old Stone Age analog circuitry at that, pretty much a no-brainer. Problem is more a matter of ever getting it back accurate again since the part that fails is the calibration resistor. All of which is done in the most pathetic weenie failure-prone way I can even imagine for doing it. Just altogether a poor design.
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