using multimeters to test boiler faults?

[luckydub]

hello..i am a qualified plumber / gas fitter. I have been working in my trade for over 11 yrs, but mostly installating gas fired heating systems in residential area's. I have always been pretty good with fault finding on systems, and i know abit about parts on boilers but im not 100% sure how to use a multimeter to check if parts arent working or to work out 100% if that is actually the part thats not working...the easy way to fix alot of boilers is to change the P.C.B but i want to be better than that. I want to further my skill on boilers

 

[zeusfaber]

Never applied this to boilers, but I imagine the same rules apply.

You need to understand how the thing you're testing works - not just what its output normally looks like, but how it should react to any combination of inputs. This will probably mean getting wiring, pcb layout and schematic diagrams for the system (don't know how easy this will be in your field).

Then you need to work out how you can get to what is going on at every significant point in the circuit. Sometimes that's a simple "volts between here and earth" - but often you have to be more imaginative. Know how to use a voltage to tell whether a set of contacts is open or closed (after having proved the source). Know how to measure a current without breaking into the circuit (find a series resistor in the circuit). Know how to measure voltages relative to an earth you can't get to.

For some types of circuit, a cheap moving coil meter can be a useful extra tool - much easier to tell how a signal is changing and how stable it is with one of these.

After that, it's a case of finding where in the system the signals aren't what you'd expect - then tracking down which components are just giving a wrong output because they've got a wrong input, and which have an output which isn't consistent with the inputs.

A.

 

[rmw]

LuckyDub,

Anonymous sites on the internet are good places to get tips (would be an intersting name for a site wouldn't it?) and opinions but not enhance your skills. That you ask is to me in and of itself an indication to me that you are in way over your head here.

I'd suggest trying to find a trade school nearby where you can take some basic electrical and electronic courses at night or weekends, and then with what you learn there you can competently do what it is that you want to do.

Starting to poke around with a miltimeter without knowing what you are doing spells trouble for someone - could be you.

rmw