Archived Not charging, no tach

[Gio]

:{ I need to know what I am missing!

I have a 97 4x4 dually,I noticed yesterday my tach stopped working and that my alt. wasn't charging.

Today I had the alt. rebuilt but that didn't fix it.

I don't have any power on the feild termanals.

which wire on the ign. switch takes power to the alt.

:--) I noticed today that the A C wasn't working either except for when the tach would come on than the A C would work.

I cann't find a curcuit that is shared by these three ( tach, A C alt. )

 

[LoneRam]

Just a shot from the hip, check the Camshaft Position Sensor. Mine is on the drivers side behind the gear train. It has three wires and sends the engine rpm and timing to the ECM. Dont know if your year has a Cam or Crank position sensor but that makes sence for both problems.

 

[crabman]

Gio,

Check the large fuse(120 amp. ) in the PDC, located on d/s fender. If it is ok, then check the crankshaft position sensor connector which is located on the front of the engine by water pump. Clean connections and use dielectric grease on connector pins before reconnecting.

Have you cleaned all the battery terminals and engine grounds?

crabman

 

[Kirwin]

Tach and Alternator issues

On your 97 the sensor located below the fan pulley is not actually a crank position sensor, it is a engine RPM sensor. If this signal is missing neither the alternator nor the tachometer will not work as the PCM won't enable the field as it sees an engine RPM of zero. The connector is located up on top of the engine close to the theromostat housing. Clearence of this sensor to the vibration dampener is critical. If you look there are either 2 slots milled in the vibration dampener or elce a tone wheel just behind the dampener that porivide the excitiation for the sensor. Of course a poor sensor ground can also cause this to happen. Hope this helps. Ken Irwin

 

[Gio]

Thank you guys for your input!

Ihaven't found the problem yet,but I found someone who could bypass the PCM for the charging by taking the alt. and adding a small external regulator so it would work as a one wire alt.

But I still don't have my tach.

How can I check the RPM pickup on the crank?

 

[McCRam]

When mine went out, the grid heater didn't work either, nor could I scan the computer with the scan tool. When I unpluged the crank sensor the grid heater worked and I could scan the pcm. Seems that the pcm wont turn on if the sensor is inop, but will turn on if it is unpluged.