12 Volt Issue - Rear Patio Lights not working, and battery not charging.

[rmyers]

I have been attempting, to fix what I thought would be a simple bulb replacement of the 2 outdoor rear patio lights. When I removed the bezel, I noticed what appeared to be a halogen light that plugged into a metal housing a little larger than a USB plug. Well, after several attempts to Lowe's, and various auto parts stores, I finally pulled the little metal housing the bulb slipped into, and on the back of the metal piece were letters that identified the light as a H3-12V55W which turns out to be a standard automotive fog light.

So the type of light issue as been solved but the problem is not solved.

When I measure voltage with a meter at the light connections, I get standard 12+ voltage. However, when I connect a light to that same connection, it does not illuminate, and if I connect the light while measuring the voltage, it will drop to zero as soon as the lights are connected. If I take that same light and bring it to the front of the camper in the battery/generator compartment and connect to any one of the 12 volt circuit breakers along the bus, the light illuminates as expected.

Other symptoms discovered through this process:
The battery is not maintaining a charge.
When plugged into shore power or switched to generator power, all 120v and 12 volt interior and all exterior lights except the rear patio lights work as expected. All hydraulics and high load 12 volt systems appear to work as well.

When unplugged from shore power, generator not running, water pump does not start.

After reviewing some of documents put together by the owners, it seemed to indicate a tripped 12 volt circuit breaker, however on my system, non of the circuit breakers have a reset button.

We are leaving for Florida this weekend, so tomorrow, I will reinstall the rear lights, and hopefully be able to troubleshoot the problem once we arrive at our destination.

Any help troubleshooting this would be greatly appreciated.

Ron

 

[jimtoo]

Check all your 12v fuses. Check by using a test light on both sides or removing and looking at them. Do not rely on the red led to show blown fuse, because if no load on circuit the led will not be on.

Jim M

 

[wdk450]

Modern Digital Volt meters (DVM's) are high impedance devices. That means that they use minuscule amounts of the circuit current while measuring the voltage. This also means that while DVM's can show if voltage is present, they cannot (in the voltage measuring mode) tell how much current flow is available to do the work of lighting the lamp. The voltage is like the pressure in a water hose, the current is like the flow in gallons per minute. All of this is to say that you have shown that the circuit cannot deliver the needed current, most likely due to a poor connection (think kinked hose) somewhere.

Troubleshooting this sort of problem is best done with a test load light instead of a DVM. Get a socket or solder leads onto an incandescent 12 volt bulb. Connecting 1 lead of the lamp to a known good 12 volt DC source, you can use the other lead to the lamp to test for good ground return by touching it to bare wire places on the ground (white)wire. When you encounter a good ground the bulb will light brightly. To test the positive side of the circuit, connect 1 test wire to ground. Then whenever you touch the other wire to any good 12 volt DC source, the light will light brightly.

I once had a problem like this at work with a cable, the DVM said it was OK, even the resistance measured O.K. But when I took the connector off one end of the stranded wire I saw just 1 strand making a connection. When I soldered all of the rest of the strands back in place, the cable worked normally.

 

[TravisJen]

Like Bill said, your problem is likely high resistance in the circuit either caused by a loose connection, pinched wire or corrosion.
H3's are a signal wire bulb that uses the body of the bulb as a ground against the fixture. They commonly get corrosion on the fixture itself were your battery ground is soldered to it.

 

[danemayer]

Other symptoms discovered through this process:
The battery is not maintaining a charge.
When plugged into shore power or switched to generator power, all 120v and 12 volt interior and all exterior lights except the rear patio lights work as expected. All hydraulics and high load 12 volt systems appear to work as well.

These are important symptoms. If all interior lights work on shore power, but not when unplugged, the power converter is working but the battery is not getting charged for some reason.

If you look at the mini-circuit breaker buss bar again, and located the breaker that has a large diameter red wire on each side, that's the one that is suspect. Check the voltage on each side of that breaker (picture below),

Also, check the ground wire coming off the battery to make sure it's tight at the other end.

 

[Bob&Patty]

Are you sure that you have a good ground going to the lamps?? You should also look at the convertor and make it is still plugged in to the 120V plug behind the rear basement wall. Mine had come unplugged. You can build a test lamp like Bill stated....but can buy one for $20 and keep in the coach. How about at the switch....do you have 12V and ground there??