tach failure 1990 f350 7.3.. please help!!

[Shane86]

Tach works when it wants, sometimes not at all.. I have replaced alternator, eec relay, trailer tow relay, soleniod, neutral safety switch, throttle positon sensor, tach sensor, cluster, and the batteries cleaned and tightened all the grounds . Sometimes when i start the truck the tach works but as soon as i turn the truck off and restart it the tach will not work. have tried everything I can think of.

I have not changed the speed sensor would that cause the tach to act up?
J

 

[madpogue]

Speed sensor is unrelated. What have you TESTED?

 

[franklin2]

Wiggle the wiring to the tach sensor while the engine is running and someone is watching the tach. See if that makes it start working.

 

[chris142]

Mine don't work when its cold outside.

 

[Shane86]

Tested ohm on sensor to teca 2700 max. Cleaned grounds an retightened them wiggled all wires to sensor nothing. Traced wires all day today nothing broke or loose

 

[Shane86]

Chris 142. Does it send your trans into safe mode?

 

[chris142]

Mines a stick shift