Tach/RPM not working help!!

[808Gt]

well my tach/rmp stopped working for some reason, everything else works but the tach?! can anyone with this problem help please...

 

[Kdubslugga]

The tach gets its signal from the Coil on the drivers fender well. Its only 1 harness with 4 or 5 wires in it, check and see if maybe a wires is loose???? Not a hundred percent on this but i think the green wire is the tach signal

 

[jrichker]

Aftermaket tachs read the signal coming off the coil.

The stock tach reads the IDM signal on pin 4 of the computer (dark green/yellow wire). There is a 22K ohm resistor in line with the wire. If the wire or resistor breaks or goes bad you will get a code 16 and the tach will not work. Check the wiring connector at the TFI module for damaged dark green/yellow wire, loose or dirty connections.


Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Wiring & Engine Info Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

 

[808Gt]

Thanks for the replys... So I found the resistor and it looks good from what I can see.. Buy is it possible to just replace to, or is there away to check if its still good?!

 

[Haus]

doesnt the Tachometer have a fuse in the fusebox?? If so you may want to check that to rule it out

 

[jrichker]

An ohmmeter or DVM can be used to check the resistor. Be sure to read the instuction manual for the meter and understand it clearly before you check out the resistor. Check it before you replace it. If it checks good, then it is not the source of the problem

Radio Shack has the resistor - 99 cents, Model: 271-1128.

See Ford Fuel Injection » How To Solder Like a Pro for some excellent tips of soldering wires for best electrical performance.

 

[808Gt]

update: checked the resistor and its good. dunno what else it could be? also I had to take the bulb out of the engine oil light because it would stay on.. I have oil, so dunno why would the tach not work.. hmm do you think getting another cluster would work?