dancutlass

I am currently trying to get my courtesy lights to work properly.
There is power at both ends of the fuse with the ignition off and also at the ends of the orange wires.
The white wire provides good ground as well, my test light is always shining when I hook it up to both contacts in the socket.
So far so good.
Now when I put a bulb into the socket, that's a totally different story, because then I have no power at all so the bulb won't light up.
Does anybody have an idea to solve that mystery?
Thanks Dan

tru-blue 442

Just thinking out loud Dan.
Doesn't the under dash socket
have to be grounded in it's location
under the dash to provide a solid ground
for the rest of the lights?

MDchanic

Your test light should NOT light up when you test the white (ground) side of the circuit, as it is grounded (at least when a door is open or the headlight dimmer is turned all the way).
If you are saying that the test light lights up on both sides of the bulb when the bulb is in the socket AND the doors are closed, that's different.


No. Ground is completed through each switch.

- Eric

oldcutlass

If you put the bulb in and have power to both sides of the lamp, then you are not getting the ground provided by the door switches.

dancutlass

Thanks for your answers so far guys! I will update a picture I took, to clear things up a little I didn't mean that the test light lights up when I test the white side of the circuit, what I really meant was, that it lights up when I use the white ground wire as ground, while testing the orange one.
Sorry for my bad english
When I put the bulb in however, I have no power at all, neither at the orange wire, nor the white one.

dancutlass

IMAG1016_zpsfe134ef6.jpg

oldcutlass

What are we looking at there Dan? I'm assuming it's showing voltage, what happens if you put the bulb into the circuit. If it goes away it means a bad connection somewhere.

dancutlass

Yes you're right, Eric! It's showing voltage and if I put a bulb in, the test light indicating voltage goes out.
So what do you mean with a bad connection? What should I search for and where?

Jetstarjim

Hmmnn... your LED test light does not pull very much power, maybe giving the illusion you have a good ground? Maybe the conventional bulb is pulling more power, thus causing your ground failure?

oldspackrat

This may be a stupid question, but are you 100% sure you're using the correct bulb? Also maybe check the voltage to that socket with an actual voltmeter to see if you're getting battery voltage there?

MDchanic

Here's the thing: A voltmeter, whether digital, LED, or mechanical, is an extremely high resistance device, and draws essentially no current.

Because of this, a source of current at the end of a high resistance run may show full circuit voltage when no current is flowing, but as soon as current actually flows (as soon as you put the light bulb in), the resistor prevents significant current flow, and the measured voltage drops to zero.

I would check it with a proper 12V test light (like an 1156 bulb with two wires soldered to it), and see whether current flows.

You may have a very high resistance spot somewhere, most likely in the fuse box, but it could be at any connection point in the circuit.

- Eric

oldcutlass

What you have is just enough conductivity to activate the led as Eric said above. It may be that the door pin switch is just barely touching and when a real load is connected the circuit opens. Similar to a battery and corroded terminals, it'll read 12v all day but it won't allow the starter to do anything but click. Will the bulb light if you rotate your headlight switch? A light bulb is a controlled short circuit.

Jetstarjim

Besides a good "old fashioned" test light, one of the entry level "power probes" is almost a must have for the hobbyist. Mine has a few more functions on it, but the basic one is pretty reasonable. It's probably one of my most borrowed tools, and often followed by an "I should have bought one of those along time ago". They are great for chasing down electrical gremlins.

MDchanic

I dunno. In the past 35 years, I've never had more than an 1156 bulb soldered to two wires and a multimeter, and I've never had that "empty feeling"...

- Eric

Lady72nRob71

Try changing the fuse (swap with another if you do not have a spare).
Sometimes the link inside separates from the end caps and will open up under load such as when the light comes on. With no load, current will pass.
Sounds odd but I have seen it several times.

5998DownUnder

Make sure the end of the bulb is goes down far enough into the socket to make contact. The pins may be sitting in the correct way in the slots but holding the bulb up too high off the contact.


I had this problem. To test, I folded up a small piece of aluminium foil and put in the base of the socket then inserted the bulb. That was my problem, then the solder for a permanent fix.


Sometimes a dob or 2 of solder on the base of the bulb extends that base just enough to make a contact.


Failing that run extra earth leads (ground leads).

johnnyjaws

u shouldn't have powr going to both wires 1 power oneground

Jetstarjim

Well, it was just a suggestion. I've found mine to be very useful, and just thought I'd share the information on it. I'm somewhat reluctant to accept newer products as well, still having lead paddles and files that see less and less activity. If your set-up works for you, wonderful! I never anticipated a "right" or "wrong" answer. Have a great day!

MDchanic

I'm just busting your chops. I do tend to go the "old fashioned" route myself a lot of the time, though.

My grandfather was a body man. He'd worked with lead since the days of the Model T.
Never taught me a single thing about it. He said that when plastic (Bondo) came in, it was a godsend, and you'd be an idiot to use lead, so he wasn't going to talk about it (I'm not saying that about you - that's what he used to say to me 40 years ago).
He tended to be opinionated.
I sure wish he'd taught me about it now.

- Eric

twintracks

The ground has to come through the door switch. I'd try pulling the door switch, and touch the wires directly to the body to see what you get. If you have rust on the threads, or grime at the switch contact point, you will get these symptoms.

dancutlass

Many thanks to all of you, as usual y'all were very helpful!
The fuse box turned out to be the culprit, the contacts are rusted badly, causing the effects the Erics described above! I thought I cleaned the fuse box pretty good already, as everything else works, but maybe these are too far gone to make a reliable contact.
Replacing the whole fuse box doesn't sound too attractive though :-/
At least I have a nice BP90 soldered to two wires now, which I will use more often than the led in the future for sure ;-)

oldcutlass

Glad you fixed it.

MDchanic

The metal terminals inside the fuse box are available from one of the aftermarket wiring harness vendors - we had a discussion about it on here about a year or two ago, but I don't recall which vendor it was.

Glad you got it working!

- Eric