Technical => Electrical Tech => Topic started by: t3skidoo on December 12, 2007, 10:03:45 PM
Title: max degrees of sweep for factory tach?
Post by: t3skidoo on December 12, 2007, 10:03:45 PM
TC buttstuffog gauge package, how high will the factory tach read?
Title: max degrees of sweep for factory tach?
Post by: softtouch on December 15, 2007, 04:14:40 PM
From the '84 shop manual: T-Bird/Cougar 2.3L TC engine tach has an 8000 rpm range.
Title: max degrees of sweep for factory tach?
Post by: grutinator on December 15, 2007, 05:17:04 PM
it'd suck to get to, but you could always put 12 volts on it and see what it pegs at
Title: max degrees of sweep for factory tach?
Post by: t3skidoo on December 15, 2007, 06:59:02 PM
Thanks for the responses.
I've got an instrument cluster out of the car. I can try that shocking it. Any idea on how much amperage to give it?
Title: max degrees of sweep for factory tach?
Post by: grutinator on December 15, 2007, 07:08:22 PM
not sure. check the instrument panel fuses (idk if we have an individual tach fuse, if so check that) and try not to exceed that amperage. (ie, 20 amp fuse, shoot for 18 or so.) going over shouldnt really hurt it if you only do it once or twice for a second.
Title: max degrees of sweep for factory tach?
Post by: t3skidoo on December 15, 2007, 07:45:24 PM
thanks, I'll give it a shot.
Title: max degrees of sweep for factory tach?
Post by: MasterBlaster on December 16, 2007, 06:18:08 PM
No, no, no, no, no, no, no, no, no, no.
Did I mention "no"?
You do not apply a positive voltage to a tachometer's signal terminal that's designed to measure how often it's given a negative (ground) signal.
This is not the gas gauge, or temp gauge, both of which use a simple heated bi-metal strip to move the needle, and which are specifically designed to "peg" when voltage (though only 5v!) is applied to them.
Try shoving power into the tach in the wrong direction, and you'll likely fry its circuit board.
Title: max degrees of sweep for factory tach?
Post by: grutinator on December 16, 2007, 09:18:49 PM
i apologize for giving you wrong information. i didnt know that the tach got its power (or ground in this case) differently then normal gauges. again, i'm sorry
Title: max degrees of sweep for factory tach?
Post by: t3skidoo on December 17, 2007, 01:48:37 AM
Thanks for the update. Too bad I fried two tachs in the process.
[/joke]
I'm too much of a procrastinator to get to it that quickly. Now that I know how to *not* test the tach, is there a correct way without using the gas pedal?
Title: max degrees of sweep for factory tach?
Post by: TurboCoupe50 on December 18, 2007, 09:52:21 AM
Quote from: MasterBlaster;193077
No, no, no, no, no, no, no, no, no, no.
Did I mention "no"?
You do not apply a positive voltage to a tachometer's signal terminal that's designed to measure how often it's given a negative (ground) signal.
This is not the gas gauge, or temp gauge, both of which use a simple heated bi-metal strip to move the needle, and which are specifically designed to "peg" when voltage (though only 5v!) is applied to them.
Try shoving power into the tach in the wrong direction, and you'll likely fry its circuit board.
This is GOOD info, but I don't think the tach will care what voltage(within reason) is fed to the signal input... Either 12v neg or positive, it's just going to set there, NEEDS a PULSE to trigger it... I've connected them to a small transistor radio speaker output and watched them dance to the music...
If you really want to know I can pull a '88 off the shelf and move the needle with my finger... BUT the '87-'88 tach is totally different internally than a '85-'86 and has a 7K scale...
Tom
Title: I've got both types
Post by: t3skidoo on December 20, 2007, 09:53:10 PM
Quote from: TurboCoupe50;193388
If you really want to know I can pull a '88 off the shelf and move the needle with my finger... BUT the '87-'88 tach is totally different internally than a '85-'86 and has a 7K scale...
Tom
What I want is a factory-appearing tach that accurately reads to 8K-9K. If the factory 85s will read to 8+ then all I need is a new face. On the other hand, if the gauge itself needs something or needs to be replaced, then I'll pull the factory tach and go from there.