!2v Guru needed

[Cousin Jack]

What I thought would be a simple exchange exercise is proving a little more demanding....removed one old 12v cabin light, put a new one on, nothing! Having changed bulbs etc, I eventually put a meter on the supply, 12.56v present, lights before and after working, put a load, (std bulb, that works!), in the circuit, and the meter reads 0.00v!

Any thoughts??

 

[Cloven]

Long shot but is the new one an LED bulb? Sometimes the polarity matters with these bulbs.

 

[Cousin Jack]

Nope, standard 12v type.

Long shot but is the new one an LED bulb? Sometimes the polarity matters with these bulbs.

 

[elton]

What I thought would be a simple exchange exercise is proving a little more demanding....removed one old 12v cabin light, put a new one on, nothing! Having changed bulbs etc, I eventually put a meter on the supply, 12.56v present, lights before and after working, put a load, (std bulb, that works!), in the circuit, and the meter reads 0.00v!

Any thoughts??

You've got a bad connection somewhere, which is working until it has to pass significant current. Probably a corroded bullet connector, or a dirty or corroded bulb socket.

 

[G12]

This one is easy but it might be a bugger to find. There is a corroded connection somewhere that is preventing the circuit from carrying load. I'd use a test bulb at various points to chase it back until you find the issue. A bulb will provide enough load to recreate the fault.
Try checking at the switch/breaker first.... at least you'll have a good starting point then...

 

[Cousin Jack]

Thanks Chaps, that should keep me out of trouble for a while!!

This one is easy but it might be a bugger to find. There is a corroded connection somewhere that is preventing the circuit from carrying load. I'd use a test bulb at various points to chase it back until you find the issue. A bulb will provide enough load to recreate the fault.
Try checking at the switch/breaker first.... at least you'll have a good starting point then...

 

[VicS]

Thanks Chaps, that should keep me out of trouble for a while!!

Without doubt a bad connection


One of the pitfalls of using a digital volt meter. They take so little current that they give a normal reading despite there being a bad connection.

A test lamp. ( a small bulb on a couple of leads ) is what you need ........ or even the meter with a small bulb in parallel

 

[fergie_mac66]

worth swapping bulbs for led , the power saving is more than worth it .

 

[nigelmercier]

... or even the meter with a small bulb in parallel

You have just reminded me that I plan to make up a lead with stackable 4mm banana plugs connected to a 24V lamp.

 

[Cousin Jack]

Without doubt a bad connection


One of the pitfalls of using a digital volt meter. They take so little current that they give a normal reading despite there being a bad connection.

A test lamp. ( a small bulb on a couple of leads ) is what you need ........ or even the meter with a small bulb in parallel

That's what I did when tested under load, (bulb and meter)....old habits etc.

Thanks

 

[lw395]

One thing that exhibits exactly this behaviour is those fuses which have an LED which light up when blown....

 

[prv]

One of the pitfalls of using a digital volt meter. They take so little current that they give a normal reading despite there being a bad connection.

+1 - I ended up buying an unnecessary replacement fridge controller as a result of this mistake

Pete

 

[nigelmercier]

You have just reminded me that I plan to make up a lead with stackable 4mm banana plugs connected to a 24V lamp.

I can order some extra parts if anyone wants them.

New thread started http://www.ybw.com/forums/showthrea...-Buy-Stackable-Voltmeter-Plugs-Lamp&p=5222569

 

[nigelmercier]

One of the pitfalls of using a digital volt meter. They take so little current that they give a normal reading despite there being a bad connection. ...

See demonstration in this thread:

New thread started http://www.ybw.com/forums/showthrea...-Buy-Stackable-Voltmeter-Plugs-Lamp&p=5222569