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--- opinion:frater_secessus:troubleshooting [2024/08/10 11:13]
frater_secessus [resources]
+++ opinion:frater_secessus:troubleshooting [2024/12/10 17:24] (current)
frater_secessus [narrowing it down]
@@ Line 17: / Line 17: @@
-==== noticing "normal" ====
-There are at least two different kinds of //normal//.  Both are important to understanding how your system is misbehaving
+There are at least two different kinds of //normal//.  Both are important to understanding how your system is misbehaving.
-=== normal for your system ===
+  * normal **according to the specs** - the DC-DC charger is rated at **40A**
+  * normal **for your setup** - maybe you see **37A-38A** in Bulk while driving down the highway, and **25A** at a stoplight.
+After you get plenty of "seat time" in your rig you will know what is normal for your setup. Until then you really only have the specs for comparison.
-=== normal according to the specs ===
+==== taking inventory ====
+Knowing what you have is important.  It helps you understand what should be happening, and helps you communicate any problems to folks who might be able to help.
+If you built your own system you know what is where and why (you put it there!).  If you bought an all-in-one the manual will say what you have.  [[opinion:frater_secessus:prebuilt_van|Figuring out a prebuilt van]] may be the hardest of all since you might not have all the information, or parts might be hidden from view, etc.
+=== hardware ===
+The hardware is the physical //stuff//:  components, wires, fuses, lights, fans.  Look for brand and model info on everything and store the list somewhere for future reference.
-==== taking inventory ====
-=== hardware ===
 === software and settings ===
+This includes apps (name, OS, and version), firmware (version), and any settings or profiles that exist.
@@ Line 53: / Line 63: @@
 ==== what is actually happening? ====
+There is a famous saying that
+> **clearly stating the problem** is 90% of the solution
+Sometimes just //asking// the question aloud or writing it down triggers something in our understanding of the situation.
+It can help reveal faulty assumptions about //how things work// or //whether or not they are working right now//.  A "second pair of eyes" is also helpful in spotting faulty assumptions.  Get used to asking yourself questions like
+  * how do I know that?
+  * is that really true?
+  * did I actually test it?
 ==== when did it start? ====
+if it **worked before and doesn't work now** then at least one of these may be true;
+  * an electrical connection is compromised:  wiring terminal loose, fuse blown / breaker tripped
+  * something was inadvertently turned off by physical switch or app setting
+  * something has failed or worn out((like batteries))
+if it **it works sporadically** then there is likely a loose connection or failing component.  These can be tough to diagnose for reasons discussed in the next section.
+If **it's never worked** then perhaps
+  * something is installed but not hooked up or turned on (see above)
+  * it wasn't installed
+  * it failed before you bought it and the seller didn't know or didn't say
+It's also possible that it's **working as designed** but you don't know it. Example:  "[[electrical:solar:status#setups_with_no_float|my charger isn't charging my lithium batteries]] even though they are not at 100%".
 ==== is it repeatable and predictable? ====
+When we can **cause the problem at will** we are very close to the goal line.  We truly understand what is happening and all we need to do is figure out why.  Sometimes we can google at this stage and get a direct answer:  "firmware v4.3 has a bug where [yadda yadda yadda]."
+Getting to this point can be time-consuming and frustrating.  It's basically repetitive testing and observation until you can make the problem happen with the minimum of factors.
+==== narrowing it down ====
+We've come this far in the process and **this is our first attempt at doing what most people think of as troubleshooting** (testing with [[:#multimeters|a multimeter]]).
+=== measuring voltage ===
+Measuring voltage with a 'meter is fundamental to troubleshooting in a van.  Let's assume a lava lamp plugged into your 120vac circuit no longer works.  Anything between (and including) the battery and lava lamp could be causing the issue.
+There are many points to test
+  -  the 12v battery bank voltage at the terminals
+  -  the 12v input terminals on the inverter
+    - the 120vac output terminals on the inverter
+  -  120vac outlet where the lamp is plugged in (assuming it's not directly plugged into the inverter)
+In practice we usually don't need to test them all.  We can make some fair assumptions on our preliminary investigation:
+  * if voltage at the battery is low (lead) or ~zero (lithium) the battery needs to be charged. If voltage is normal the problem probably lies elsewhere.
+  * if other things are running off the inverter right now then the problem is unlikely to be the inverter itself.  Note, however, that it's possible that the lava lamp pushes the inverter over its limits.
+  * if nothing is running off the inverter and there are not lights on it then a fuse may have popped. 0v at the inverter inputs will help confirm this.
+  * if the lava lamp doesn't run when connected to a normal shore power outlet at Starbucks then the problem is probably the lamp.
+If things still don't make sense we might have to explicitly test those assumptions.  Or test at each point.
+  * if the battery terminal voltage sags under load the battery is undersized and/or unhealthy
+  * if battery voltage is ok but low at the inverter terminals then the [[electrical:12v:voltage_sag|voltage sag]] is likely caused by resistance.  Bad connections, undersized wiring, etc.
+On wiring runs that do not have observable loads on them we might have to take a voltage reading at each one.  If there are many connections you might start at the midpoint to rule out 50% of the possibilities, repeating until you find the offender or exhaust the possibilities.
+Note:  on circuits presently carrying power voltage testing is also indirectly continuity testing (see below).  If there is voltage there //must// be continuity between the test points.
+=== measuring current ===
+Sometimes voltage doesn't tell us what we need to know.  Finding a parasitic load is often done by watching current going out of the battery and pulling fuses one at a time or otherwise breaking the subcircuits.  When the offending circuit is taken offline the current will drop by that amount.
+Current measurements are also important for understanding how your system is functioning:  how much charge you're getting, etc.
+If you have [[electrical:12v:battery_monitor|a battery monitor]] installed you can watch the net charge/discharge that way.   Or you can use a clamp meter (see below).  Or for small currents you can break the circuit and use the meter inline reveal the current.    The clamp meter is the fastest, easiest way to measure current on a particular wire.
+=== measuring continuity ===
+Meters can measure continuity.  This might be useful for testing a fuse in the hand;  it might look good but actually be popped.
+=== measuring resistance ===
+Meters can also measure resistance but that is beyond the scope of this simple guide.
+=== testing components ===
+==== tools ====
-==== where does it start? ====
-We've come this far in the process and **this is our first attempt at doing what most people think of as troubleshooting** (testing with a multimeter).
 === multimeters ===

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