Help with electrical testing

[Johnysmall]

Worcester Bosch Greenstar Junior 24i

I was called out to one of these today because the owner had "No hot water"
Old, small terraced house, 2 up 2 down.

Done preliminary checks and I found that:

Hot Water
Sink is next to boiler, open hot tap, diverter valve moves to DHW position, boiler fires up, then cuts out within a minute. The water doesn't get hot in this minute, just lukewarm for a few seconds, then cold. Clicking noises every now and then from boiler as though it wants to fire but nothing happens.

Heating
Property has 1 rad downstairs in living room, 2 upstairs and a towel rail in bathroom. Room stat in living room.
Boiler control turned to max, room stat @ 30 and rad valves open. Boiler fires up and stays on for approx 2 minutes, off for approx 3 mins, back on for 2 minutes etc etc. during this time return pipe back to boiler is just lukewarm, all rads and towel rail lukewarm, room stat reads temp at 15 degrees.

No fault codes shown on lights during DHW or CH operation i.e Blue light on constant, reset light off.

The instructions assume that any competent person working on the appliance is a qualified electrician, either that or I'm an idiot because I don't have a clue when it starts telling what to test for electrically.

Flow Sensor Test
:Replace control board if: 5V is not across the red and black cables.
:1.5V-3.5V is across the yellow and black cables (with water flowing). Otherwise replace flow sensor

Where exactly are the cables?

 

[picasso]

you will find the cables on the plug st9 on the pcb and the other end on the flow sensor although I dont think that will be your problem.

 

[Johnysmall]

Thanks for the first part of your sentence , but the second half is rather useless to me unless you care to elaborate?

 

[Agile]

These questions are best asked in the CC forum.

Its not clear to me on what basis you are going to these properties but if you are offering a boiler breakdown repair service then its essential to have a very good understanding of electrical testing procedures otherwise you will be seriously struggling with most repairs.

Tony

 

[Johnysmall]

These questions are best asked in the CC forum.

Its not clear to me on what basis you are going to these properties but if you are offering a boiler breakdown repair service then its essential to have a very good understanding of electrical testing procedures otherwise you will be seriously struggling with most repairs.

Tony

Most of my working life in the past 3 years has been fitting council/housing trust bathrooms, kitchens and heating systems. Thats my working week Monday to Friday, it's not nice but it's work and the moneys not too bad. I could probably do the lot with my eyes closed by now but my knowledge is pretty much limited to this work now. Every now and then, time permitting, I will do other work which is usually for a mate/family etc. This is in my spare time, against my better knowledge and the pleas from my kids, and usually unpaid or for pennies.

I got a call from a mate Saturday morning that his mate had no hot water, has a baby, etc etc, can I take a look. I took a look, noted my findings and as I was a bit unsure thought I would be better off asking advice in this forum, as come Monday morning I'm going to be back throwing the council stuff in and not having a minute to think about it.

So as you see I am not offering a boiler breakdown service, but I am none the less qualified to work on boilers. So I will now copy and paste my original post into the CC and hope one of you guys can help me out. With any luck I can pick up whatever I need late tomorrow afternoon and hopefully fit it during the evening. Otherwise I will just tell him to get someone else in as I simply don't have the time.

I hope this clears up any queries and really hope one of you can help me out.

Cheers