Did not you say that you connected the charger backwards? WOw, what you did then was send positive DC voltage to ground. That means that anything tied to ground (such as the PCM) saw positive DC voltage @ 50A come through the ground plane. That is huge. Do you know how much 50 A of current is? 12 VDC @ 50A? It's huge. I work with electronics all day. I am an engineer and let me just say that all of your components just saw that voltage across all the ground legs which, I hate to say this but, you may be looking at some serious damage to your entire electrical and electronic systems.

Inside those PCMs and sensors, there's tons of ICs, one way diodes, polarized caps, logic circuits and various other voltage sensitive components that, when you run that kind of voltage into the wrong way- it FRIES them instantly. The caps blow, the diodes open up, the resistors cook, the ICs fry etc.

The headlamps will still work as those are just 12V battery lamps on a simple switch. It is not a polarized circuit meaning voltage can go through bidirectional and it still lights up. No damage done there but, as for the rest, good luck. Usually, there's a failsafe fuse to prevent that from happening.

 

I meant the starter circuit since the ecu and other electrical doesn't seem to be effected. Sorry for not being clear, but yes the starter and battery is new.

 

That clicking that you hear; that's your ASD relay. It is a failsafe mechanism that is engaging. It's basically a kill switch to prevent fire or other catastrophe from occurring. You may need to have someone professional who specializes in electrical go over the entire electrical system with a software diagnostic tool.

 

what's a asd and where's it located? The truck did start tonight so I believe the ecu is ok.

 

sorry I replied before the page loaded. I think I'll go to a salvage yard and pull some of the wiring.

 

You can't run that motor W/O a PCM but, it still may be damaged. So, not to be hard on you or anything like that, but, me personally, I would not assume that the PCM is fine. I would assume the worst and have it tested.

The ASD is located in the master fuse box inside the engine compartment to the right hand side of the battery when standing at the driver side fender well. The cover has a map of all components residing inside. You read the cover as it's laid out on the fuse block. Remember to REMOVE all DC voltage prior to removing any fuses by shorting out the two battery cables together. Take both off the battery and touch them together. This will drain any stray voltage that may be stored and prevent a back-feed voltage into the fuse block when removing a relay. Normally, all you have to do is simply remove the neg cable but, in this case, we don't know if there's a charge stored or not due to the voltage reversal and possibly damaged power suppression diodes.

NOTE: If the battery cables are not connected to the starter, touching them together will not do any good as it's not completing the circuit. They need to be reconnected. FYI

 

I'll take care of that, could it be possible the wire from neg to the alt was cooked since it started with the alt out but triggered the asd when it was put back in? I did test the pos cable to the starter and it was ok I'm going to replace it anyway. I have no idea where to get that neg cable since it has the connections for the alt.

 

The dealer will have that harness but, there's two grounds coming off the ALT. One is from the harness and is a smaller AWG and, one is off the battery that is a larger AWG that grounds to the ALT bracket which grounds to the engine block via a stand-off coming off the intake manifold.

Now, to fry that wire- would take some doing and, it would have to be completely severed by electricity.

Test it by first doing a continuity test on it and note the ohms. It should read near zero to about 1 ohm of resistance. I highly doubt that the wire is severed. I can't be sure as I don't see what you see but, the AWG on both grounds is pretty beefy to just pop like a fuse. I don't see that happening. Conducting it - sure. But, that's about it.

When we look at where the current went, it just flows on all the black ground wires to the block as a dead short. You see, if you had the battery in the circuit AND had positive of the charger going to ground- well, you now have two things going on. One is the battery is applying current the right way while you are sending 15V DC going the other way and, since it is all connected, it's basically a dead short as your connecting positive to negative be means of the external charger. You are very lucky to not have blown the battery.
DC is direct current too. It is very destructive. It is not like AC which is somewhat forgiving during a mishap.

DC is one way. You were flowing it both ways and, that's very damaging.

So, you see, your not going to pop a heavy wire like that as it's made to handle that current. Doesn't matter which direction as the wire doesn't care which way the current flows as it's engineered to handle that voltage and amperage. The wires are not damaged. It's a component/s that are damaged thus not allowing a proper startup.

Your alternator is a generator. It is a simple mechanical device that works by rotational movement. It has a stator and a alternating rotor. It generates both an AC and DC voltage. But, the AC side needs to be rectified in order to produce DC voltage. AC must be passed through a diode bridge / rectifier. The result is DC voltage is generated and that voltage is fed to your battery directly to charge it.

Now, what happened when you connected it in reverse, you had sent + VDC directly to ground where all the rectifier diodes tie into essentially killing them. In layman terms, you killed your ALT rectification stage and, that's why when you put it in circuit- the ASD relay shuts it down. It senses that something is out of whack and kills it. Now, when you remove it, there's no feedback so, it allows the vehicle to start up w/o it.

 

I had the alt tested and it was ok, if I take all current out of the system like you said and clean all grounds think it will give it a shot? I can do almost anything on my 73 charger because the electrical is so simple but these computer controled systems are pretty complicated.

 

I borrowed a code reader, showing no codes and all systems are working. I was not surprised there was no codes since I pulled the battery. Changed the starter wire still nothing. A friend of mine was saying theres a graphite washer on the alt. which keeps the wire from shorting out, and would explain why it cranked better when I had the alt disconnected?