Fuse Blowing - Jaguar Combi Bolier

[slippery]

Hi guys.

Hope you can help with this little problem. I was asked to have a look at a fault on a Jaguar wall hung combi boiler. There are two fuses on the PCB. One is 1.6A and the other is 80mA. The 80mA fuse is blowing intermittantly for no apparent reason and there is no pattern or associated other faulty component that I know of. It can last a few hours or a few days. Does anyone have any idea as to what may cause this fuse to blow?

 

[tamz]

Doesn't help when it is a pile of junk you are looking at.
It is something you would need to be there when it does it. Putting a heavier fuse in may damage the board so do that at your own risk.

Speak to the manu and see what they say. They may have had it before.

 

[mountainman]

If you can download the MI's you may be able to identify what the fuse feeds,
80mA isn't a lot so may be gas valve of a diverter motor.

 

[Mike Jackson]

The instructions give no idea of what the fuse feeds. The instructions are probably worse than the boiler, which is saying a lot.

 

[mountainman]

Next idea then
What stops working when the fuse is removed.
I.e. Fan works with fuse in, doesn't work with fuse out.
A very simplistic scenario but the principle holds good.

Another thought, do you know what voltage is present at the fuse?
It could be low voltage AC or DC, knowing this may help in identifying the component causing the fuse to blow.

 

[M.Joshi]

According to the manual (page 33), Fuse 1 T80mA seems to be for the main boiler control circuitry and display.

Fuse 2 T1.6A is for the pump, fan and ignition module.

http://manuals.arated.com/index.php?d=Boilers/Jaguar

Are you replacing the 80mA fuse with a time-delay one (T80mA)?

Fuse 1 is probably after the main transformer as it is such a small value. It may be blowing due to ageing of other components on the PCB or intermittent water ingress into the PCB. Can you see discolouration anywhere on the PCB?

 

[jtsplumbing]

Its a jag boiler, load of junk made by Glow-Worm for Plumb Center, see if you can talk them into a replacement. Probly got a faulty PCB.

 

[glenno1]

Try checking pcb for any scorch marks or possible arcin,if not already done so

 

[slippery]

Guys

Thanks for all the suggestions and I do agree it is a pile of junk but that said a fault is a fault.
For more info. There are no other obvious signs of component failure, arcing, water damage etc. and the fuse does not rupture on power up but at some later time that can be a few minutes to a few days.

 

[mountainman]

Sounds as though a component fed by that fuse is drawing more power than it previously did and gradually shortening the life of the fuse.
I reckon it's a test meter jobby, do you have any friends that are keen on electronics that can trace the circuitry?

 

[M.Joshi]

Was the fuse replaced with a time-delay one? If a standard fuse was fitted, it may eventually blow whereas a time-delay one (as specified) will be tolerant to power up surges etc.

 

[mountainman]

Was the fuse replaced with a time-delay one? If a standard fuse was fitted, it may eventually blow whereas a time-delay one (as specified) will be tolerant to power up surges etc.

Should have been, you suggested this some time ago

 

[M.Joshi]

Should have been, you suggested this some time ago

Just checking as slippery hasn't mentioned what type of fuse was replaced

 

[zzzjim]

Got any details of how power is fed in . Modern house with RCD / old fuse box and Spur or socket ?
Far more likely problem is in boiler , but dirty power can blow fuses like this !

 

[krafa]

Just to recap, I think you said it is an intermittent fault, how many
times has the fuse blown and over what time period?
My friend's boiler is installed in the loft and has been subject to
extreme swings of temperature in the last few weeks and therefore highly
likely to have had condensation problems. Plummer