I've replaced the alternator X2, the battery, solinoid, ECM module, and its still not holding a charge. I was told there might be a fuse in the engine compartment for the battery but I don"t have a manual or schematics. Any ideas????

 

sounds to me like you have a parasitic load thats draining the battery when the truck is parked

 

What you have is an unusual, unintended and for real current draw off of something that needs to be found, evaluated, and fixed (there's no such thing as parasites or for that matter, any organism in there, the cause of the problem will be actual, for real, demonstratable, explainable, and will be pinpointed). Get a voltmeter (china freight has cheapos on sale for $3), remove a battery cable, and connect the meter between the batt and the cable. Now set it at the lowest amperage setting that produces a reading on the meter and doesn't peg it. Bear in mind that the ECM and radio will have a small draw (maybe 50 - 100 milliamps) at all times. Disconnect these known current draws from power for now because they are valid and expected (but watch to see how much they are drawing because, and albeit very rare, a malfunction in these items could be the problem). Now watch the meter (set to read amperage), which surely is going to show other than zero, and start removing fuses one by one. When you finally remove a fuse that causes the meter to show a zero current draw, you will have isolated the circuit causing the problem. Now with this knowledge, you can focus on finding the culprit within that circuit that is causing the excessive current draw and killing your battery.

Identifying the circuit with a problem is usually very easy, isolating the problem in that circuit can take more time. Culprits can include failed relays (like the time out relay for the dome light), bad brake light switches, and a bad reverse light switch to name a few of the things I've found while fixing peoples rides. I haven't found any parasites in any mechanical or electrical system ever, and never will.

 

Its most likely a short circuit. There isn't a "battery fuse" to really look for. Check your grounds. have you replaced anything electrical lately?

 

I'd scratch the short circuit from the list. Why? He's not blowing fuses (and telling us about it), he has said nothing that would indicate that a circuit breaker is cycling, and any short of significance is gonna make things smell funny if it's not tripping a protective device. It's very unlikely, but I suppose there could be a component short in his radio that is cranking up the draw to, say one amp, and which would not blow a fuse, but he's gonna figure that out when he goes in there with an ammeter and performs the diagnostics, isolating the circuit that is causing the heavy draw. Time to do this should be about 20 minutes.

 

Ground wiring and connections… how is it ?

Is the engine to battery ground strap in place ?

Is the engine to body ground strap in place ?

 

Looks like another one post wonder.
He probably hasn't noticed his dome light stays on all night long from a dirty door switch.

 

Newby just needs to remember to come back !

It does sound like something is pulling is draining the power; maybe a load test will help ?