Multimeter Novice

[mrmills]

Just started using a multimeter on doing polarity and voltage checks as initial checks but looking to venture into testing parts on breakdowns such as fans, gas valves etc does anyone know a good website or book to refer to or any advice would be appreciated.
Just a point does it matter which probe (red or black) goes onto which connection when checking componenant ?! thanks

 

[Jonwells]

Multimeter checks are the way forward to diagnose correctly, not many manufacturers print set values for various components. I know the game quite well, but I now talk to technical when I'm in front of a faulty boiler, they will tell you the values you should be getting. Alot of boiler faults (all cheaper boilers) are what i call "two jobs" there is one fault that has caused another, just talk to the manufacturers technical, most are great, but beware some are premium rate 86p per minute.

 

[mrmills]

Thanks for the prompt reply. Some good pointers, but if say testing a gas valve, if i pull the connection off, does it matter which one the red probe goes to and the black probe as some wires are grey and black etc same on APS does it matter which probes i use for the C, NC or NO ?!?

 

[arran197]

You will be testing resistance, so no it doesn't matter. Usually the one solenoid is roughly half the other, buy you will need to check with the manufacturer.

An APS will be continuity, on the C to NC when no fan running.

 

[stevetheplumber]

theres no polarity when doing resistance so no doesnt matter which way leads are
for switches (over heat stats,aps, low water sensors) your not usually testing resistance just make or break of the switch
mostly when testing motors (pumps fans etc ) youll either have a resistance figure which is good or youll have no resistance or open circuit

 

[dontknowitall]

There are a couple of YouTube videos on the basics of multimeters.

 

[quality]

Your red and black leads only really matter when your measuring DC voltage polarity as AC will be the same either way

 

[BGB1]

Mr Combi does a good DVD which takes you through testing components and your basic electrical checks.
You can find details on the web and order a disc.

 

[johnnyplumb]

Best book for repair work combination boiler fault finding & repair John reginald