I feel like I'm missing something simple.

The passenger side reading lamp stopped working. I've replaced the bulb (checked in a different socket), checked the switch & the fixture with a multimeter.

I get 12 Volts in the fixture socket(so the fixture ground seems OK), but a "10Amp" test doesn't get a read (a similar test of a "live" fixture gets me sparks...obviously a difference...no amps?). A continuity test of the fixture with the bulb in it reads slightly more than the bulb itself, so the fixture continuity seems OK.

What am I missing?

Don Julien
2003 Adventurer 33V

Don - I think you have a marginal connection in there somewhere. A connection may be able to show continuity, but will open up when you try to pump some amps through it. This would explain the failure of the "10Amp" test and the failure of the light.

With the bulb in the socket and the switch on, try measuring voltage across any and all connections associated with the socket and switch. If the continuity is good you should read 0v across a connection. If you read any voltage, there is a resistance or an open circuit. Of course you should read 12v across the bulb since that is the load that's dropping all the voltage.

Sounds like a grounding issue to me double check the ground or even re-do it to be sure.

In any electrical/electronic device the most common problem is the socket or the connector (or switch/relay in that case). Mechanical devices are just not as reliable as electronic devices. What you want to know is whether 12 volts is across the lamp terminals (not the socket) when it is turned on. If the lamp measures ok with an ohmmeter, then it has to light if voltage is applied.
Good luck form Jena, Germany

Lesson learned: Don't trust a multimeter. After being confused about whether I should be getting a voltage reading when I check for voltage, or whether I should be getting continuity when checking for continuity, I just said what the heck & grabbed a couple of wires.

Stretching a long wire to a known good ground (no result), I used a short wire to jump the terminals on the switch. Voila, light happens. So, the switch indicated continuity in the "on" position, but it wasn't passing juice.

Thanks to "tomsm" for the idea that a switch showing continuity might be opening up.

Don Julien
2003 Adventurer 33V

quote:

I get 12 Volts in the fixture socket(so the fixture ground seems OK), but a "10Amp" test doesn't get a read (a similar test of a "live" fixture gets me sparks...obviously a difference...no amps?). A continuity test of the fixture with the bulb in it reads slightly more than the bulb itself, so the fixture continuity seems OK.

I agree with Tom in that you have a bad connection somewehere. A bad connection can carry voltage with no load like when you measure with a meter, but when you put a load on it (bulb) the volatge drops due to high resistance. You have to check the entire circuit while switched on and the bulb installed and now start measuring the voltage from the bulb back to the supply source

http://www.jrprvinc.com/rocker_switches.htm