interior lights not working off battery power

[mainah]

The radio draws very little power if there was an issue with the breaker it's possible for it to work but not the load of the lights I would bet had you turned on the light the radio would have gone off.

[JohnB]

Hi Bob,

I agree with mainah on this one is a possibility. The radio display is drawing milli amps and a single light bulbs draws 1.4 amps. It is not a stretch to think a self resetting circuit breaker can fail in an amp draw mode. Meaning you may get a little something to pass but not enough current to do much more then light up a crystal display of a radio.

Originally Posted by mainah

The radio draws very little power if there was an issue with the breaker it's possible for it to work but not the load of the lights I would bet had you turned on the light the radio would have gone off.

BTW, when you put your volt meter on the 2 terminals of the breaker you where actually measuring voltage drop across the breaker. Since the LP detector is always on when the disconnect switch is on there was a path to DC common through the LP detector and that one side of the breaker was more negative than the other. The voltage drop should be very low to almost nothing when measuring like that. You are basically measuring the voltage drop of a component part in a circuit and in this case the defective breaker. However while voltage may pass, that does not mean large current will which "sounds" like the case you had.

When you put your meter on 1 post of the breaker and then the other lead on the DC common or frame, then you are measuring the battery voltage (potential) to DC common. This is different then voltage drop across a component. There was some level of affected resistance of the components between the battery and where your test probe was to DC common but should not be enough to drop the voltage very much so it should of read close to battery voltage.

Here is a simple explanation of voltage drop and compares it to fluid pressure drop in the hydraulic world. Fundamentals of Electricity


You did real good sorting this out. Pat yourself on the back!!

John

[mainah]

This is one problem of using a DVM they do not load a circuit so you may read 12 volts but the circuit is not capable of carrying a load. Most often for testing 12 volt systems I use a test light. If I really need voltage reading then I switch to a DVM.

[GoodoleBob]

Well it is fascinating to read what the electrical guys write on the problem I had, but somehow it never sinks deep enough into my mind to be of lasting worth. So the next time I have electrical issue trust me, I'll probably ask most of the same old questions again.

Think of it as a reason to visit SOC and chat with old friends...

[Gene]

Originally Posted by GoodoleBob

... trust me, I'll probably ask most of the same old questions again. ..

As you know, we welcome the questions AND we like to hear from old friends.