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Author Topic: 92 4cyl Tach problem  (Read 7032 times)
408ciw
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Location: Yadkinville, NC

« on: August 23, 2014, 03:10:05 pm »

Have a 92 4cyl mustang, the tach has quit working. Shutdown mode tach reads 0, on engine running mode tach reads ~4500 all the time even while driving. Ideas where to start troubleshooting.
Thanks
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rob342
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Location: darien, il

« Reply #1 on: August 24, 2014, 10:59:05 am »

MY 92 GT did what you describe. actually mine would show 0 with the car off, 4000 at idle, and it would go up from there when i revved it.

the fix was to solder 3 resistors. here's a step by step:

1- remove the instrument cluster
2- remove the screws around the clear plastic, and also those holding the black trim around the guages.
3- take the clear cover and black plastic bezel off and set it aside.
4- don't try to remove the needle. there is no need.
5- remove the tach assembly from the cluster. the circuit in need of repair is on the back of it. there is some sticky tape on the left edge holding it in, but the gauge, it's guts, and the face will pop out in one piece pretty easily.
6- if you study the circuit board on the back of the tach, you will see that one corner has two small black resistors and a larger resistor in the same corner. if you shine a light through the board, you will see the discoloration and know you're looking in the right place. i used the flashlight on my iphone because it's slim enough to fit in there
7- resolder the six terminals for the three resistors and your tach will work properly again. i bridged some of the solder joints together to make sure my fix is permanent.



this post from the corral is how i learned where to look:
>>
Finally got the tach fixed after replacing TFI, computer, etc. I finally took it to a mechanic in Jupiter, FL and they thought it was not the tach itself because I had tried the used cluster I had bought and had tried another used cluster, all of which did the same thing (reading of 4000 rpm). They ordered another tach from FORD but, because it didn't arrive on time, the mechanicc took the tack out of the used custer and it had a broken circuit at a transistor (or diode or something). He soldered it and it now works just fine. He also fixed my other one because the same thing was wrong with it
<<

i'm no wiring genius, and it wasn't very much to go on, but i figured it out. im sure you will too. let me know if this works for you.
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white 92GT, with a black interior, pony rims, 5 speed with a 3.73 gear. came with a gear, exhaust, and a powerdyne. nice little cruiser, i didn't change much yet.

have tw170's, systemax II, 75mm accufab, anderson n41, t5z, ford racing 23lb billet flywheel, and a quarterhorse sitting here. cam may change
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