What to test with a multimeter?

[John_]

Can anyone give me guidance what I can test on a combi with a multimeter and what to look for. Many thanks in advance.

 

[AWheating]

this question would be better suited to a closed forum. Have you joined the gas safe registered forum yet?

 

[diamondgas]

John_ :lol: that's kind of scary if you're doing repairs and charging folk... IMHO!!! Not saying you do mind 🙂

But off the top of my head you can check............. oh! Feel freee to add to this list anyone:

polarity
earth continuity
dc voltage
ac voltage
resistance of motors
resistance of coils
ntc resistors
switch continuity
wire continuity
electrode resistance to earth


Okay dried up 🙂

What you look for is a discrepancy in what you expect John_ ... Why do you ask by-the-way?

 

[GQuigley67]

get yourself on some training courses, boiler manufacturers, fault finding, using multi meter etc, it can all be very new and confusing if you dont do it all the time, took me a while to take it all in as its something i dont do everyday and still useless at it !

 

[John_]

Booked myself on a boiler fault finding course later this month. Just want to prep myself and hopefully impress the tutor. Yep, I am a teachers pet. 🙂

 

[Masood]

Booked myself on a boiler fault finding course later this month. Just want to prep myself and hopefully impress the tutor. Yep, I am a teachers pet. 🙂

Out of interest, which manufacturer course, and where?

 

[diamondgas]

Booked myself on a boiler fault finding course later this month. Just want to prep myself and hopefully impress the tutor. Yep, I am a teachers pet. 🙂

If you want to impress then learn how components work! How for example does a gas valve open up to allow gas through? How does an air pressure switch actually know a fan is working? those kind of things will live with you for ever and serve you well regardless of your tutor IMHO 🙂

 

[diamondgas]

How does a little probe know what temperature the water is and 'tell' the gas flame to get smaller? How does the boiler know there's a flame, the pump is running, I am actually asking it to give me some heat?? They're good things to learn too 🙂 Love it! There's a lot to learn about the intricate working of a heating system we all take for granted John_ ... One step at a time my friend ... 🙂

 

[John_]

Thx all. Will study a bit harder. From what I've gathered so far things to look for are, pump, fan, air pressure switch, solenoid, thermistor, overheat stat, ignition, motorised valve, and obviously the usual dead tests and polarity, what else do I need to look for? I am more interested in components wise.

 

[John_]

Am I right in thinking that the thermistor will tell the boiler that temperature has reached? What test do I need to do to find out this is not faulty?

 

[John_]

Just one little boiler hanging on my kitchen wall, and yet so much to learn. 🙁

 

[glenno1]

Try to get a few components and test them,i found that the best way i.e see what thermistor does when you warm it up

 

[diamondgas]

Am I right in thinking that the thermistor will tell the boiler that temperature has reached? What test do I need to do to find out this is not faulty?

Do a google on Negative Temperature Coefficient resistors .. It'll melt ya brain 🙂

 

[diamondgas]

Try to get a few components and test them,i found that the best way i.e see what thermistor does when you warm it up

Really good advice 🙂

Instead of just throwing things away after replacing them try messing about with them, get familiar with how they work ... It'll help you know end, promise 🙂

 

[John_]

How does a little probe know what temperature the water is and 'tell' the gas flame to get smaller? How does the boiler know there's a flame, the pump is running, I am actually asking it to give me some heat?? They're good things to learn too 🙂 Love it! There's a lot to learn about the intricate working of a heating system we all take for granted John_ ... One step at a time my friend ... 🙂

The ignition sequence I understand, pump on, fan on, air pressure switch closed, ignition start, solenoid open. Is this correct? I really want to understand.

 

[John_]

Do a google on Negative Temperature Coefficient resistors .. It'll melt ya brain 🙂

Will do, thx 🙂

 

[diamondgas]

The ignition sequence I understand, pump on, fan on, air pressure switch closed, ignition start, solenoid open. Is this correct? I really want to understand.

Not all boilers need to know that the pump is running, however they do need to know that a fan is running! How weird 🙂 But then a pump has nothing to do with the safe removal of the products of combustion yeh?

 

[johnnyplumb]

The ignition sequence I understand, pump on, fan on, air pressure switch closed, ignition start, solenoid open. Is this correct? I really want to understand.

if you want to learn about boiler repairs, start with this book

Homepage - Central Heating Combination Boilers - Fault Finding & Repair Book

 

[tamz]

"Fault Finding & Repair’ is the latest publication from author John Reginald, a Gas Safe registered heating engineer."

I wonder if there is more money to be made writing books on how to do it than actually doing it.........mmmm i'm not getting any younger :lol:

 

[Bernie2]

Have a go Tamz! Why not?