Corrosion. 12.5VDC dont mean sh!t

[bonanzadave]

I hope Jim (Posplayr) will shed some "light" on this.

I was trouble shooting the inop dome light in my truck topper. Easy. Check the voltage at the bulb socket. 12.5 VDC. Bad Bulb. Nope. ???? There is 12.5V at the socket ! Two bad bulbs ? Nope. WTF. 12.5VDC on both sides of the fuse. A+ wire ohms out to the light socket. Bad ground ? Nope. Ground wire ohms out to the light socket. WTF !!! Crawled under the truck and found this badly corroded splice. Replaced it with a new splice and.....

How does the corrosion allow voltage but resists current ?

[chuck hahn]

be sure to use some dielectric grease on the new splices and clean up all the other connections and grease them also.. that will avoid many problems down the road.

[Dave8338]

I hope Jim (Posplayr) will shed some "light" on this.

I was trouble shooting the inop dome light in my truck topper. Easy. Check the voltage at the bulb socket. 12.5 VDC. Bad Bulb. Nope. ???? There is 12.5V at the socket ! Two bad bulbs ? Nope. WTF. 12.5VDC on both sides of the fuse. A+ wire ohms out to the light socket. Bad ground ? Nope. Ground wire ohms out to the light socket. WTF !!! Crawled under the truck and found this badly corroded splice. Replaced it with a new splice and.....

How does the corrosion allow voltage but resists current ?

Though I'm no electrical wizzard by any standard, is not the voltage, the "allowed current" through a given passage and the Ohms resistance the electrical equivelant to the "pressure"?

Geeezzzz, Dave. that could have all been avoided if you would have bought a Ford!

[Steve]

Very good illustration why there should never be spliced connections under a vehicle.

Even if it had been wrapped with a bunch of tape, water would still have found its way in.

.

[duaneage]

Resistors are made from different materials that allow some flow but not much. Transistors and diodes are made from unique materials that allow current flow in strange ways.

In the light socket case you're looking for no monkey business, just low resistance. The green stuff looks like copper that has oxidized pretty bad. Try not to ford streams so much and you should be fine.

[Nessism]

Very good illustration why there should never be spliced connections under a vehicle.

Even if it had been wrapped with a bunch of tape, water would still have found its way in.

.

What I was thinking to...only I'd say to never use scotchlock connects period, inside or otherwise.

[Dave8338]

What I was thinking to...only I'd say to never use scotchlock connects period, inside or otherwise.

AGREED~!

[850GT_Rider]

Using a digital voltmeter?

Watch out when checking for voltages with a digital voltmeter. The input impedance is so high that a mere trickle voltage is enough for them to register.
You'll have better luck using one of the 12vdc trouble lights. I've added a really long clip lead to the negative side of mine. Clip it to the -side of the battery to check for 12 volts. Clip it to the + side and you can check for ground continuity. And I still use an analog VOM a lot. Much more dependable than a digital unit sometimes.

[Detroit Diesel Man]

AGREED~!

Double that agree here...we get those issues at work allllll the time..truck driver spends $200 on fancy lights and then installs them with those damn connectors..or worse yet..ive actually seen people use wire nuts..as in house wire nuts...a nitemare to trackdown and very costly to re-wire a set of 25+ lights correctly when it should have been done right the first time...they should outlaw those scotchlocks.

DDM

[bwringer]

Scotchloks are evil. Eeeeeeeeeeevil.

[posplayr]

Yes indeedie

http://www.thegsresources.com/_forum/showthread.php?p=1174217#post1174217

And that is why electrical engineers invented "full load" tests

[posplayr]

By using a DIGITAL VOM and not the conventional/analog type, that's how.
You are not the first or last person to be fooled by a digital VOM.

Please explain the empirical or theoretical basis for your conclusion.

[BIKERTUCKER]

I'm an electronics tech by trade. My take on this is the faulty connector could pass 12vdc to the socket with no load (no bulb filiment) But once bulb was installed and circuit loaded (bulb filiment)the corrosion in the connector provided the path of least resistance and passed the small amount of current that should have been going to the bulb and went to ground. Not a short that would blow a fuse more like the corrosion created a poor mans resistor to ground. Agree with never use these snap connectors. Once removed over thirty of them on an old Goldwing. My choice is 40/60 solder and heat shrink.

Take care

Tim

[bonanzadave]

Got it.....

Scotchlocks - Bad (I actually knew that)

Get a (maybe two) test lights.

Smart ass replys - Ask Mr. Dave8338 (I actually knew that too)

Empirical or theoretical conclusions - Ask Mr. teddux (could you fix my TV ?)


Thanks guys ! I see the light !!

[DanTheMan]

Scotchloks are evil. Eeeeeeeeeeevil.

But they're Easy. EEEEEEEEEEEEEEEEEEEEEASY!!!!