Archived help no alt/no tach, cruise light on in steering wheel

[randyco]

My 96 3500, 5spd has lost tach, alt charge and the cruise switch on wheel is on. I replaced the engine speed sensor still nothing. Swapped pcm from a 98 12v auto truck starts but still nothing. I hotwire the alt and it charges fine. I tested the 3 pin connector at the speed sensor and I have 3. 7v at 2 of the wires and 1 has ground. WHAT NEXT?

 

[K5IP]

You are on the right track, and I still think you are missing the speed sensor output to enable the pcm.

One lead to the sensor is a refrence voltage from the pcm. On my 95 it is 5. 2Vdc.

A ground lead to the pcm is also provided.

The third lead, the output lead switches between the reference voltgage and ground each time the notch in the damper passes the sensor.

This lead may measure the same as the reference with a vom unless you are very carefull to look for small changes, and it may be more easly observable while cranking the engine over with the starter (fuel selonid disabled).

I find an oscilliscope is the easiest way to check to see if the sensor (hall effect sensor) is actually switching so if you have access to a scope, thats the way to go.

I wonder about your reference voltage. It is lower than mine but I think they made a change to do just that later on so you may be ok.

If you need more info, just ask, orf pm me.

Rog

 

[AOwens]

Check your crank sensor. mine did the same thing. about $125. 00 if thats is.



Adam