19 minutes ago, VWD said:

Lee- if it's a HR earth problem, them a meter will show circa 12v between lamp pins 2 & 3. Far better way is to connect a sidelamp bulb  across pins 2 & 3 and then measure voltage. With a good supply ( +12 nom) and a good earth, the reading will be the same as that of battery ( give/take a small voltage). If there's a bad earth / supply voltage, then the voltage read will be a bit lower. ( Bulb will draw the rated current through any HR).

 

I was trying to establish whether 12 volts was even reaching the connector multiplug relevant wires before going further. The end result all adds up to the same thing whichever way you do it.

Edited 20 December, 20196 yr by TMB

I know that, Lee, BUT ( AND IT'S A BIG ONE), a digital meter will only present a very high impedance to the supply volts. Meaning that it most likely will not detect a problem with either a HR feed or a HR earth line.  its down to OHMS law. e.g. An HR of low resistance ( say 10 ohms ) will drop the supply volts across a 5W lamp by 5 volts. Measure the voltage on lamp with a high impedance meter and it will read (nominal) 12v . Place  5w lamp in circuit and the voltage across the lamp will show as (nominal 12) minus 5 =7 volts. Something often missed by folks looking for a HR fault with a modern voltmeter .

A modern digital meter will confirm the presence of 12v on the  connector pins, but measuring across the pins with a 5w lamp in circuit, WILL give the true voltage to light the lamp.

Edited 20 December, 20196 yr by VWD

Yeah I know what you're saying. I usually use a 12v test bulb myself with this sort of problem.

For HR faults, it's possibly better to get hold of one of  ye olde low resistance meters ( somewhere like 1000 ohm/volt) or better still even lower.