Alright boys so I finished re-wiring my engine bay a few weeks ago everything is working great. I was getting a charge of 13.5 with the factory alternator/pcm regulator(92 cummins truck) now I'm getting 14.7 with a one wire alt along with everything at a fuse block now with the proper fuses and the alternator routed to its own mega fuse/holder and then to the battery. I know the 1 wire does bypass the asd relay which is pretty much useless on these trucks and I understand that it takes its signal from the crank sensor at a certain rpm and then runs to the alternator with the pcm/regulator wire. Now my question is should I just disconnect my power wire that goes from the asd to the fuse block? On these Cummins trucks they do not really do anything, but support the factory voltage system/alternator which the one wire phases out. Cel is on due to the open circuit for the relay(code 42) considering the removal of the original alternator and the removal of the asd wire(green w orange) and pcm wire(green). From my understanding I read that for some reason a tach signal is required to bypass the computer and close the relay.

 

42 Automatic shutdown relay circuit open or shorted

The alternator really has nothing to with the asd relay, Do you have a aftermarket/gm alternator(one wire)? In gas motors it will supply power to the coil injectors and 02's. Not sure how it works on the diesels. But if the pcm doesn't see the motor has started it will shut off the asd relay. You should see if the pcm is at least turning it on during cranking/start up. If the pcm doesn't see the motor is running will shut it off. If you don't already have one get a wiring diagram and see if anything is not wired correctly.

 

I have gone through all the diagrams the asd routes to the alternator(green w orange), it routes to the duckfoot from the factory which now is at the fuse block(power wire), it routes to the ignition switch, and it routes to the pcm as well on two separate circuits. I can hear the pcm turning the asd relay on after starting the truck and once the crank sensor realizes the engine is above 400 rpms at idle. It's a Pa performance one wire alt.

 

I'm just gonna attempt removing the power wire from the fuse block and see if that turns it off. I already tried removing the relay itself, but that didn't do anything.
Update: yea just had to remove the power wires one comes out of the relay and one comes out of the pcm.

 

i don't understand why you switched to a 1 wire alternator? stock style should have been just fine. only thing is if the computer goes bad you have to install a older style voltage regulator. also the computer should be getting the tach signal from the crank position sensor which should be on the front of the engine. realistically the computers on the diesel engines are not really that important and i am surprised that there is something serious enough to trigger the check engine light and even then it doesn't mean anything on those things. a lot of people even go as far as bypassing the computers on their truck since they are not really needed.

 

alternator fuse kept blowing everytime I disconnected the negative and reconnected. Problem solved with the 1 wire and like I said 14.7 is a helluva lot better than 13.5. Those voltage regulators don't hold up whatsoever and I installed an internal regulator on the old alternator as well which I properly installed per the fsm and it did not function properly. Voltage kept shuffling and I have read just about all the diagrams for these 92-93 trucks. The crank sensor ties in directly to the pcm and then sends the signal to the asd relay via the pcm/key on in regards to engine speed for proper voltage/power supply to the alternator/generator field. My goal is to keep everything working properly which is why I decided to not just unscrew the bulb for the cel.

 

what alternator fuse? there is a fusible link but that shouldn't be failing easily unless there is something wrong. if you replace it or installed a fuse that would likely be why a fuse is popping. they are not as forgiving as fusible links. also you can buy a good voltage regulator that are adjustable. have never had an issue with voltage regulator's or the stock style alternators. at this point the computer is pretty much entirely bypassed. even overdrive is on a switch.

 

Ya didn't read the entire thread bub

 

brand new 6 ga power wire(1 wire) from the alternator to the fuse and 00 ga wire from the fuse to the battery. Same wires that I used with the factory alternator and kept blowing the fuse when disconnecting the negative battery terminal. Now with the 1 wire no problem.

 

You probably had a diode or two bad in the alternator causing it. Bad diode causing a short in the alternator reconnect the battery and the fuse blows. New stock style alt would have fixed it.