Archived tach quite working/ voltage gauge discharging

[APAGE]

While driving down highway tach began to bounce upand down, then quite working altogether. When this happened the air conditioning compressor shut down and volt gauge dropped to 10-12 volts, I pulled over and looked around under hood nothing unusual. Turned engine off and then restarted. It began working before I could get back up to speed it started again. Still that way this morning. I would appreciate any ideas. Thanks Al

 

[JThomas]

tach and volt quit

Had that happen to me. The alternator quits, the cruise control quits, the air quits, the tach quits. Mine was bad tach sensor located on the front of the engine, just above the damper. Way the computer works, if the engine rpm is low or zero, don't need all the other stuff to work. Low rpm, cuts off the alternator until rpm able to sustain output. Unit is about 75$ at Dodge. If that is the problem, I think that is a Cummins part, at about half the price. Should be able to ohm unit when dead. Your's is probably a broken wire, usually right at the sensor, or a bad connection in the plug. Trace the wire and clean the connection. If it is a broken wire, the flexing of the cable lets it make and break while driving, until it never comes back again. IT WILL COME BACK otherwise. Let me know how it turns out.

 

[APAGE]

Thanks jthomas for your reply i will check that. Yesterday while it wasn't working I pulled fuses trying to find a grounded system, when i reinstalled fuses cranked truck and everything was working again. Will check that wire to sensor. Thanks again .

 

[GAmes]

Truck profile??

It would sure help if you had one. At any rate, if you have TDR issue #39 check out page 42, topic "Charging system".

 

[Woodenhead]

Had the same deal with my crank sensor. Pulled it off and found it was covered with junk. Blasted it off with some electrical cleaner (Swish I think) and put it back in. That was a year ago and no problem since. I think these sensors work on magnetism so I'm not sure how the crap covering would cause a problem. Maybe I just jiggled the wire or plug the right way.



Good Luck

Mike

 

[LandShark]

Ditto on what GAmes said. Would help to know year of your truck and miles. I would consider this to be a normal failure mode of the alternator if you had high mileage.