Thought I would share an experience I encountered yesterday while on a service call. The customer had a 2 year old 5th wheel and was complaining about the 12 Volt lamps burning up. Yes burning up! Upon arrival I see maybe as many as 10 or 12 cheap plastic lamp housings with dual 921 bulbs and integrated on/off rocker switches ALL of them showing severe heat related issues. Some with melted lens and some with a melted rocker switch each and everyone with discolored lamp sockets. My first thoughts wow he was lucky to not have a fire. Voltage at the lamps measured a constant 14.8 Volts. Found the battery disconnect switch was in the off position with the converter outputting a constant 14.8 Volts. Turned on the battery switch and watched the voltage drop to 13.2 after several minutes. Cleaned up the lamp sockets with some contact cleaner as best that could be done under the circumstances and STRONGLY suggested replacement of all the lamps with LEDs ASAP. I wonder how many fires those cheap junk lamp assemblies have caused over the years.

Why was the converter putting 14.8 v into no battery?Jim

HiTech wrote:Why was the converter putting 14.8 v into no battery?JimThis is just a guess, of course, but obviously the converter was in the OMG-the-battery-needs-a-full-charge-it's-almost-dead mode. Sign of a good converter, IMHO, trying to do right by the battery that wasn't there.My concern is that the fixtures were being burned up by a mere 16% over-voltage. I agree that this is a sign of really cheap fixtures, and that the owner needs to immediately replace all the bulbs with LEDs, AND to remember to throw the battery disconnect switch and hook up that battery before using the RV in the spring. And most especially before dragging that rig down any road!

Poor quality converter Could not even find a manufacturers name on itActually never seen a converter do that before - none of the dozen or more I fixed in the past year or two ever did that Checked the specifications of the 921 bulbs 1.4 amp at 12.8 VDC 17.9 watt Wonder how much more power they were dissipating at 14.8V?Enought to cause a fire for sureThe guy lives full time in the rig

how do you know the converter isn't bad? The voltage could creep back up to 14.8 once the battery is fully charged?

I do not know if the converter is bad or not..……But I doubt itI do know it is not a quality device by any stretch of the imagination I asked the guy to measure the voltage the next day as in Today Might hear something this afternoon and might not Just hope he replaces those cheap lamps SOON

Potential Fire Hazard | Good Sam Community

KJINTF
Explorer
Jul 05, 2013
Sounds as if all you folks are experts on this issue - thanks for the comments

The converter works with the battery connected, it was at 13.2 Volts the next day. The converter is a no name POS and my volt meter measures both DC and AC and even the ac content on top of the DC voltage (ever use a DVA? a common tool needed in most outboard engine repairs)

Bottom line the lamp assemblies are the problem the CHEAPEST junk I have ever seen. As Mex stated the manufacturer saved a few cents on each of them. 921 bulb rated at 17.9 watts w/ 12.8 VDC applied so maybe just less than 20 watts per bulb at 14.8 Volts then just shy of 40 watts (two bulbs) in a small plastic enclosure with cheap compression fit connectors you have a problem. The entire point of the post nothing more

Good quailty LEDs (with internal regulation) at least the ones I use in my rig easily handle 14.8 Vdc - no failures in three years while the MS TS MPPT 60 solar controller does it's thing.

Lets close this thread and move on to something more productive
LittleBill
Explorer
Jul 05, 2013
honestly what does it matter?

alternators do 14.4 all day long, never seen any lights in my stuff burn out at 14.4

i think something else was going on personally

i have also seen my pd2345 go over 14v when charging, pretty much normal

don't have a single melted enclosure
john_bet
Explorer II
Jul 05, 2013
My thought is that if battery is disconnected then nothing in couch should work period. Convertor should not be directly connected to dist. center if you have a disconnect. Just the way I would want it.
MNtundraRet
Navigator
Jul 05, 2013
MrWizard:

You missed the point. A converter/charger, WITHOUT A BATTERY (battery was on "disconnect"), should only output 13.2 volts.

The charger portion only goes into either "bulk" mode (14.4 volts), or "Absorption" mode (13.7 volts), when the voltage in the circuit drops below 12.5 volts (requires battery in circuit because charger senses lower voltage across the battery terminals).

No battery and the converter supplies 13.2 volts. Any overload should show up as lights flickering, or shutdown of the converter (abort signal or a blown fuse).
2oldman
Explorer II
Jul 05, 2013
KJINTF wrote:
Voltage at the lamps measured a constant 14.8 Volts... STRONGLY suggested replacement of all the lamps with LEDs ASAP.
And those better be good voltage-tolerant LEDs or they will just blow out too.
MrWizard
Moderator
Jul 05, 2013
for the converter,
whats the difference between battery and light bulbs, there is a current drain
i will agreed it should have timed out and drop the voltage

MNtundraRet wrote:
The converter/charger should only output around 13.2 volts if battery(s) are charged, or on disconnect. A working charger would go to around 14.4 volts if it sensed a draw from week batteries.

I suspect that the converter/charger is faulty, but with the battery(s) on "disconnect" the converter/charger may have been fooled by a erratic short form a bad light fixture to sense battery(s) needed charging.

I would have expected with the voltage output seen that the charging unit would have aborted charging, or a fuse blowing. The converter/charger has poor voltage regulation, and possibly the converter was fused on the wrong side of the circuit.
BFL13
Explorer II
Jul 05, 2013
We need more info. A two year old RV will not have a 1985 style converter! Let's spill the beans here and get the model of Rv and then maybe we can chase down what converter those things have. Then evaluate the situation.
tpi
Explorer
Jul 04, 2013
I'd go under the assumption that even with battery in the circuit the voltage would float back up to 14.4 volts at times. If the right light bulb is installed then the fixtures do not have sufficient margin to deal with reasonably typical voltages. LEDs should solve the problem.
MNtundraRet
Navigator
Jul 04, 2013
The converter/charger should only output around 13.2 volts if battery(s) are charged, or on disconnect. A working charger would go to around 14.4 volts if it sensed a draw from week batteries.

I suspect that the converter/charger is faulty, but with the battery(s) on "disconnect" the converter/charger may have been fooled by a erratic short form a bad light fixture to sense battery(s) needed charging.

I would have expected with the voltage output seen that the charging unit would have aborted charging, or a fuse blowing. The converter/charger has poor voltage regulation, and possibly the converter was fused on the wrong side of the circuit.
wa8yxm
Explorer III
Jul 04, 2013
That kind of thing is typical of some converters.. NOTE that your volt meter may have been in error as well..

There are, for this discussion, 3 types of converters

One: Magnetek 6300, I do not think this applies so that's all I'll say about it, but I could be wrong, it has very poor voltage regulation and may give false readings on some voltmeters (Digital ones mostly)

Two: Poorly FILTERED Regulators. (NOTE this class also includes the one above) these may, and for the same reaons, give false readings on a digital meter They are designed to use the battery as a giant filter capacitor. They do respond EXACTLY like the O/P's

Three: Well filtered power supply/converters.. I have, from time to time, accidentally hit the disconnect on my batteries so I was running 100% on the converter.. My Kenwood TS-2000 did not notice the difference, far as it was concerned it had nice, clean 12 (Well 13.6) volt DC coming in the power lead.

On these the voltmeter will be as accurate as it gets for that meter. NO false readings.

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