Attention: TDR Forum Junkies 
I have followed a number of threads on this subject and the symptoms seemed the same as mine.
Erratic Tachometer... normal to zero and back in a flash.
Check engine lights on and off.
Voltage dropping then rising.
Dim headlights.
I checked everything... and it all worked... it was a minor bother until one nite I had to drive 2 hours.
Well I knew the engine speed controlled the alternator... if the tach doesn't show rpm, the alternator stays off... so no charge.
Well mine was off... but occasionally it would come on... at 60 mph in 5th gear.
Interesting, it depended on my throttle setting, so I was able to limp back with a working alternator as long as I maintained 60mph. (sounds like a movie)
So I figure it has to be some wire problem... the engine twist due to torque at different rpms (or uphil) caused some kind of wiring movement.
So I started at the beginning and followed the engine speed sensor wires from the crank on up, and noticed that on my '96 there was a connector right behind the upper radiator hose... it was tightly connected, but it also had a zip tie to hold it in place... kind of weird. the Zip tie was not so tight, so I moved it and unplugged the connector.
Guess what... there was corrosion on one of the three plugs in the connector.
Could that be the problem? I took out my trusty tool (not ball peen hammer or duck tape) WD-40 and sprayed down both sides of the connector and used a small tool to clean the plug out.
I put it back together, correctly tightened the zip tie...
It worked perfectly.
So for anyone else with this problem... look here first before donating your truck to the dealership OJT training program.
Mike
Erratic Tachometer... normal to zero and back in a flash.
Check engine lights on and off.
Voltage dropping then rising.
Dim headlights.
I checked everything... and it all worked... it was a minor bother until one nite I had to drive 2 hours.
Well I knew the engine speed controlled the alternator... if the tach doesn't show rpm, the alternator stays off... so no charge.
Well mine was off... but occasionally it would come on... at 60 mph in 5th gear.
Interesting, it depended on my throttle setting, so I was able to limp back with a working alternator as long as I maintained 60mph. (sounds like a movie)
So I figure it has to be some wire problem... the engine twist due to torque at different rpms (or uphil) caused some kind of wiring movement.
So I started at the beginning and followed the engine speed sensor wires from the crank on up, and noticed that on my '96 there was a connector right behind the upper radiator hose... it was tightly connected, but it also had a zip tie to hold it in place... kind of weird. the Zip tie was not so tight, so I moved it and unplugged the connector.
Guess what... there was corrosion on one of the three plugs in the connector.
Could that be the problem? I took out my trusty tool (not ball peen hammer or duck tape) WD-40 and sprayed down both sides of the connector and used a small tool to clean the plug out.
I put it back together, correctly tightened the zip tie...
It worked perfectly.
So for anyone else with this problem... look here first before donating your truck to the dealership OJT training program.
Mike
