My son just replaced his alternator and his battery is continuing to be drained, his speed ohmmeter and his tac are not working.

Any ideas???????

 

I have purchased new alternators before that have not worked,might recheck, also on my 94 which should be the same as your 96 there is a 140 amp fuse in the fuse box that is between the drivers battery and the brake resovoir, I have not been able to find this fuse other than the dealer also the other fuses in there,goodluck Rick

 

Has the fan blower recall been done on the truck? If not, you could have smoked the wiring under the dash to the point that something is shorting and causing the drain. It has happened to several people on this board so it is a concern to look for. Tach and speedometer not working kinda point to that.

Other than that, pull the driver battery cable, hook up an ammeter inline (bigger the better) and start pulling fuses until the drain disappears. Some things will necessarily be hot all the time - clock keep alive circuit, maybe one to black box, overhead console feed? - but they should be easy enough to determine what should and what shouldn't be pulling current. Anything else, investigate.

Could be bad diode in alternator, too.

 

[quote author=redramnc link=board=13;threadid=22392;start=0#msg210493 date=1069081440]
Has the fan blower recall been done on the truck? If not, you could have smoked the wiring under the dash to the point that something is shorting and causing the drain. It has happened to several people on this board so it is a concern to look for. Tach and speedometer not working kinda point to that.


[/quote]
Tell me more. I don't like the sounds of that, and if I need to get a recall done, better before the wiring smokes than after!

 

High speed blower gets a relay to keep from pulling too many amps through the switch wiring harness. There is a TSB and recall notice - try Fritz's Ram Page and look for recall bulletins. The dealer can look up VIN and see if the recall has been done. Mine came back with a thin rubber pad on the column below/behind where the keys rub as they swing - don't know if that is a sign the recall has been done or if it is just somethng the local dealer did at the same time.

 

On this truck, if the PCM does not see an engine speed signal, it will not turn on the ASD relay, and therefore will not provide power to the alternator field circuit. Your tach will also stay at zero if the engine speed sensor (above the harmonic balancer) or its circuit is not working. Check the sensor's connector in front of the front valve cover.

 

The sensor that you need to look at is the crankshaft position sensor. The CPS is located just above and slightly to the left of center on the harmonic balancer (crank pulley). On the '96 moel the vioplet/white wire is the supply (8 volts) and the black/light blue wire is the ground. The other wire is the signal wire and it should have about 0.3 volts on it and when the slot is under it there should be about 5.0 volts on it. Check the plug for corrosion first and see what happens.
Tom