One of those confusing electrical moments

[my440]

Today while wiring up a new 12 volt in dash stereo to the house end of my motorhome I noticed when hooking the live wire up to the stereo the house lights go brighter by about 20 percent.
The stereo works fine.
This is likely not good but cant figure out why.
Any ideas?
Thanks

[wildmanbaker]

After the VOM, replace the battery charger with a real converter. I recommend a power-max boondocker, as they seem to last longer and have a 3 year warranty and multiple stages of charging, to help minimize battery damage from over charging.

[Ivylog]

Buy a $4 one from Harbor Freight... that way when you check a voltage and it's still on Ohms you are only out $4.

[my440]

Ivylog wrote:
You need to measure your DC voltage... You do have a volt meter? You probably have a dumb charger who's rated voltage is bad about boiling the water out of your batteries. Increasing its 14 votes higher is going in the wrong direction.

Will buy a voltage meter to have on hand.

Yes I have a dumb charger.
Last year it boiled up a new battery so I keep the battery unhooked and hook it up just to charge it.
Thanks for everyones help Very much so appreciated.

[Ivylog]

You need to measure your DC voltage... You do have a volt meter? You probably have a dumb charger who's rated voltage is bad about boiling the water out of your batteries. Increasing its 14 votes higher is going in the wrong direction.

[Old-Biscuit]

PoorGary wrote:
Thanks and while I grounded the stereo better the lights remain 20 percent brighter. I do like the extra light.
MrWizard thats interesting what you say. I have limited knowledge off the converter. You say theres an AC ripple in the converters DC output. Thats good right?

Tomorrow Im just going to wire it directly to the block. A previous owner had a 12 volt line he snubbed off so I hooked up to that.

MrWizard is there a way to boost up my converter giving me that brighter light?
Or do I now qualify for the most dumbest question ever?
Thanks

AC Ripple is NOT a good thing on DC System.
That is why converters have filter capacitors to minimize the AC Ripple in the DC output.

AC (Alternating Current) Sine Wave is 'converted' to a DC (Direct Current) by taking both haves of AC Sine Wave (positive/negative) and making them into a Positive-voltage Direct Current

The smoother (less wave ie: ripple) the cleaner the DC Voltage will be.
DC Electronics (circuit boards for fridge, water heater, furnace----radios etc) do not tolerate AC Ripple

You can measure AC Ripple by using a multimeter set to AC Voltage and measuring DC Voltage------ preferably less than 1V AC on a 12V DC Circuit

[my440]

Thanks and while I grounded the stereo better the lights remain 20 percent brighter. I do like the extra light.
MrWizard thats interesting what you say. I have limited knowledge off the converter. You say theres an AC ripple in the converters DC output. Thats good right?

Tomorrow Im just going to wire it directly to the block. A previous owner had a 12 volt line he snubbed off so I hooked up to that.

MrWizard is there a way to boost up my converter giving me that brighter light?
Or do I now qualify for the most dumbest question ever?
Thanks

[MrWizard]

Filter capacitors in the radio
There is an AC ripple in your converters DC output
The filters raise the voltage

Once about 20 years ago I put a filter capacitor across the wires to a 12v fan I put in the bedroom of that first class A
The fan speed got faster and the DC voltage went from 13+ to almost 16v

I was trying to stop interference from the fan on my TV
But the voltage was now too high for the lights and the batteries
And I had too remove the filter cap
Measure your house DC and see if it goes up to much
The lights should not be grounding through the radio your radio is grounded to same chassis lights..
Do not hitting the radio to the light wiring

[Dutch_12078]

Could be ground issue or it could be that the extra current load is just enough to kick the converter/charger up a step.

[MountainAir05]

better ground on the radio.