Auto Electrical ? How is this even possible plz?

sr2, Jan 18, 9:41am
The LOADpro is simply a 24 ohm resistor with a momentary off switch wired in parallel with it; it's a 5 minute DIY job to make one with junk from the shop electrical box. I prefer to substitute the resistor with a 6 watt bulb, i.e. the bulb lights up when you introduce the load.


kiwibookhunter, Jan 16, 11:18pm
Okay so to get a wof I have to fix my number plate light. I pull the thing apart find the bulb is gone, replace it, no go. so I go deeper, strip the wires back and test them, yes there is power in the power wire, it reads about 12v when the tester is connected to the power wire and the earth wire. so i get a new bulb and test it to make sure it is good first and then put the wires to it and IT DOESNT GO! how is that even possible? there is power in the wires and the bulb is good!

newtec1, Jan 16, 11:20pm
Left hand thread is your problem.

ceebee2, Jan 16, 11:34pm
The plastic fitting that holds the bulb has a faulty earth. most I have worked on have a crude earth wire jammed between the steel holder and the plastic. Consequently any excess heat can loosen this connection. Check with a meter from the steel casing to the earth with and I bet there is no continuity.

intrade, Jan 16, 11:45pm
i can tell you how its called ohms law
tell me what you used to check the 2 wires had power? did you use a volt meter by chance or what exactly?

gsimpson, Jan 16, 11:46pm
Probably a poor earth. You may be getting enough contact to drive the meter but not the bulb. Try measuring for voltage across the bulb when it is in place.

mrfxit, Jan 16, 11:54pm
Yep that ^ ^^

Try a test bulb AND holder, just jam the wires in to the clip

intrade, Jan 16, 11:56pm
both posters above are on the right path but remember high resistence is the culprit it can be in both wires , its just way more commont to have corrosion on a negative connection.
a volt meter drwas almost no current also a led testlight also draws almost no current. both can read system voltage with this low load not detecting the high resitence , only when the main bulb with a much higer current demand is inserted you get a drop to close to 0 volts
it is why you have to do a voltage drop test.

intrade, Jan 16, 11:58pm
if you want to learn this is the basics you must know to diagnose engine computer problems and anything there is ohms law apply to electronic just as it does to this simple bulb issue

jmma, Jan 16, 11:59pm
Man it's just a number plate light, give it a whack and it will go (o:

intrade, Jan 17, 12:04am
i recommend you buy your self the loadpro test leads and the book from dan sullivan the inventer and patent holder of the loadpro tester i will post a video of him demonstrating how a simply small resistance just like you have somewhere on your circuit , can shut down a huge truck and stop it from starting again.

mrfxit, Jan 17, 12:16am
LOL yea, the most often used cure for a bad contact bulb.

intrade, Jan 17, 12:22am
here is a video of how simple its done with loadpro test leads i cant find the one where he shut the truck down but this video shows how he reads battery coltage with the volt meter thru his hand. do you think your bulb would glow when you connect it to your hand as the volt meter suggests as you got system voltage.
His hand is a ultra high resister nothing more and we are conductive its why we get electricuted .
https://www.youtube.com/watch?v=7fB_G-voXgQ this is the truck shutdown https://www.youtube.com/watch?v=I8kbEsXCRfc

franc123, Jan 17, 1:22am
x1
If its obviously earthed correctly and the taiilights are working as they should then obviously there's a dodgy connection where the plate light circuit is spliced into the tail circuit. A common trap is thinking you have full power at the bulb because the meter says so when you haven't, the wire could well be fractured and only hanging together by a strand or two which simply won't pass enough current to drive even a 5W bulb. Its better to use a headlight bulb as a test light when testing old trailer circuits, it loads em up properly.

kiwibookhunter, Jan 17, 3:24am
awesome, thx for u help. ALL SORTED.

msigg, Aug 5, 9:10am
Yes basic stuff really, franc and intrade have some good examples and explanations if interested. Often a decent length wire, alligator clips, bulbs, meter you can do alot. Good stuff.

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