Light troubleshooting - mystery

[Stereo]

I have a fairly superficial knowledge of electricity so I'm willing to try to fix things myself first, but this problem has me totally flummoxed.

I have an exterior light on my camper that works intermittently. I took the switch out of the circuit and the bulb lit up fine.


I then checked the continuity of the switch and found it to be fine, but I cleaned up all the contacts to be sure that wasn't causing the issue. I then plugged the light back in but it did NOT work, even though I am getting 12v through the circuit.



I tried an LED bulb in there too, but same issue. Why isn't the light working?

Thanks for your help.

 

[Hillbilly Heaven]

Phantom voltage! Voltage is there but not enough current to light the light lol. I still suspect the switch internally. Try a different swich.

 

[shade]

Phantom voltage! Voltage is there but not enough current to light the light lol. I still suspect the switch internally. Try a different swich.

You can also do some switch wiggling to see if the lamp lights.

Bad ground contact is the culprit of many vehicular gremlins. Once you're absolutely sure the switch isn't the problem, the bulb contacts are good, and nothing's amiss at the fuse & fuse block, I'd start looking at grounds and bad insulation. There's not much else left!

 

[dwh]

If bypassing the switch makes it work, then it's the switch. Ipso facto.

 

[Stereo]

I had not persisted enough with wiggling various connections. It seems the issue is in the light socket as I got the bulb to light once by wiggling the bulb in the socket. I don't really get that because the bulb works fine and consistently in that very socket if I bypass the switch, so maybe I'm wrong about it being the socket.

I tried filing the contacts in the socket the best that I could, even though they look clean, and I tried pinching the contacts together, but the light is still not coming on. I cannot figure out if I can disengage the wire from the socket in order to work for carefully on it or replace it. The wires with their brass tips do not seem to pull out of the socket and I can't get in there to pinch the socket connectors together enough to push them back out through the socket, if they engage by tension, though again, I can't tell. Any advice on my next step?

 

[Stereo]

I'm going to try a switch I know works and see if that solves the problem. I'll get back with you shortly.

 

[shade]

If bypassing the switch makes it work, then it's the switch. Ipso facto.

In a perfectly static system, that's usually true.

It could also be the switch and another fault, or something wiggling just so during the investigation of the switch that masked the true fault.

 

[Stereo]

The winner is...dwh and Hillbilly Heaven. It was the switch. I thought I had the same problem on another light (same symptoms) but that turned out to be a bad contact on the LED bulb itself. It worked sometimes and not others. That problem was fixed with a new bulb.

DWH, being the great teacher that you are, can you please explain to me why, on the multimeter, I could read 12v through the switch if it wasn't working?

 

[Hillbilly Heaven]

It is because of high resistance. Do yourself a favor with the old bad switch. With it out of the circuit place it in the on position and measure the resistance across the connection points. You might be surprised it is high as in 100s or 1000s of ohms. Compare it to a known good switch. You will now see the resistance of the good switch is much lower. The high resistance was allowing the voltage but limiting the current to nearly nothing.

 

[shade]

A bad switch can deliver intermittent contact. For lack of a better term, they often feel crunchy when actuating them.

 

[Sparse Gray Hackle]

If I recall correctly, this was an issue that surfaced a few years back, and it was the switch that caused the problem. People were replacing them with a switch from Amazon.

 

[dwh]

Yup. High resistance, phantom voltage, call it what you will.

Switches have contacts, and, like the points in an old distributor, they wear out. Burned, corroded, dead dust mite carcasses...not making good contact for whatever reason. Good enough contact to read voltage with a meter putting a load of micromilliamps on it, but not good enough to support a load of a few watts.

No surprise if that switch is outdoors - it's certainly not a waterproof switch.

 

[Stereo]

Thanks to all of you for the education and the solution.

 

[BajaSurfRig]

Which switch did you replace it with? I have the same issue on my 1983 FWC.

 

[Stereo]

I found a mini-rocker switch at my local auto store. They only had one with a third terminal for a mini light to show when the switch was on, but I just left that disconnected. Here's a link to an online source for the two-pin type: https://www.amazon.com/5Pcs-Snap-Po...H6DZ1X26930&psc=1&refRID=471EFE1P3H6DZ1X26930