Thread: Trailer lights, multi-meters and the smoke theory

Bloody trailer electrics
Cursed damned things

Left hand indicator on the boat trailer wasn't working. I noticed this when I tried to use it last but couldn't get the lens cover off thanks to a frozen screw so left it and went boating anyway (fortunately the car lights are visible past the wee boat). Today I settled down to have a real go at fixing it ... and lo and behold, a minute squirt of RP7 had the screw sliding out happily - it had to be a minute squirt because the can decided that was the time to go empty Funny thing is, I swear it went in the wrong place.

Anyways, the screw came out ... but do you reckon the lens cover would come off? Of course not, the plastic gasket had welded everything together. Serves me right for buying cheap lights doesn't it.

So now I've got access to the bulbs ... and, of course, the offending bulb looks perfect.

Okay, I get into the car, turn it around in the driveway so the bum is facing the trailer, pick up the trailer and drag it to the back of the car, hook up the trailer and test the lights.
Nope, that indicator still isn't working ... and neither is the other side

So off comes that lens and sure enough, that bulb looks perfect too.

Wriggle everything in sight.
Resettle the trailer lights plug a few times.
Pull and tug at anything pullable and tuggable.
Give the wheel a kick.
No indicators.

So I wander inside and dig out the trusty multi-meter, which is a real hoot because when it comes to electrics, I subscribe to the smoke theory - how I ever came to own a multi-meter is a mystery, let alone two of the things.

Back at the trailer, I make a guess at where to set the dial, try the meter, try a few more settings, finally get one that provides numbers, and apply those wee probes to the right hand indicator ... which immediately starts flashing

I glared at the thing, dared it to stop working, and then went back to the left hand indicator, the original cause of all the drama.
No indicator.
No numbers on the multi-meter.
So I started trying things. Yes, there was power at the trailer plug. I tested every combination of bits and pieces in the light itself. Everything I tested said that light should be working ... only it wasn't ... until I tried the final, improbable test and that damned light started flashing.

So I now I have two working indicators (and brake lights and tail lights). They were even working after I screwed the lens covers back on

No sign of any problem though, nothing found that could have explained the mystery. Sure, I'd been moving and twisting things in the hope of clearing whatever bit of corrosion might have been stopping the smoke from flowing through the wires but with both lights, they started working only after I'd applied the multi-meter to the 'right' place.

So, in addition to the smoke theory of electricy, I can now add the fear theory. The demons that provide the smoke for the electricity are actually scared of multi-meters and if you threaten them with said meter, they start to provide the smoke. It only took me so long because I didn't know what I was doing and the demons weren't intimidated enough to act at first.

I hope to use the boat tomorrow. No, I will not be testing the lights before heading off, I can do without the drama.

Richard