Hi There,

3 or 4 weeks ago my trusty 12 year old Prima 80F boiler stopped working. At
the time I gave it a (small well calibrated) thump. It started working
again and I thought no more of it.

Today it failed again. In the specific failure mode:

....The controls are calling for heat.
....The pump is running and the fan is on.
....The pilot light is lit
....but no main burner.

I took off the bottom cover and can see the gas valve is connected to the
electrical control PCB/gubbins by a 4 way MOLEX style connector.

* If I carefully wiggle this connector the main burner lights straight
away.
* If I turn down the temperature control it turns off the main burner as
you would expect.
* When I turn up the temperature the boiler *sometimes* returns to the
failure mode.

I sense a dodgy connection or a dry joint.

Q. Is this a common failure mode?
Is there a specific connector or component that is the most common
source of this problem.
The benefit of your experience is appreciated!

David

In message , Vortex
writes
Hi There,

3 or 4 weeks ago my trusty 12 year old Prima 80F boiler stopped working. At
the time I gave it a (small well calibrated) thump. It started working
again and I thought no more of it.

Today it failed again. In the specific failure mode:

...The controls are calling for heat.
...The pump is running and the fan is on.
...The pilot light is lit
...but no main burner.

I took off the bottom cover and can see the gas valve is connected to the
electrical control PCB/gubbins by a 4 way MOLEX style connector.

A three way connector - pilot, main and common




* If I carefully wiggle this connector the main burner lights straight
away.
* If I turn down the temperature control it turns off the main burner as
you would expect.
* When I turn up the temperature the boiler *sometimes* returns to the
failure mode.

Either spurious or you have another problem


I sense a dodgy connection or a dry joint.

Q. Is this a common failure mode?

Yes - bad flow soldering, or a cracked wire in the loom connector

Is there a specific connector or component that is the most common
source of this problem.

Use your eyes grasshopper

The benefit of your experience is appreciated!

David








--
geoff

On Mon, 03 Apr 2006 23:03:11 +0100, Vortex wrote:

Hi There,

3 or 4 weeks ago my trusty 12 year old Prima 80F boiler stopped working. At
the time I gave it a (small well calibrated) thump. It started working
again and I thought no more of it.

Today it failed again. In the specific failure mode:

...The controls are calling for heat.
...The pump is running and the fan is on.
...The pilot light is lit
...but no main burner.

I took off the bottom cover and can see the gas valve is connected to the
electrical control PCB/gubbins by a 4 way MOLEX style connector.

* If I carefully wiggle this connector the main burner lights straight
away.
* If I turn down the temperature control it turns off the main burner as
you would expect.
* When I turn up the temperature the boiler *sometimes* returns to the
failure mode.

I sense a dodgy connection or a dry joint.

Q. Is this a common failure mode?
Is there a specific connector or component that is the most common
source of this problem.
The benefit of your experience is appreciated!

You've found the fault.
You might be able to make a repair with your soldering iron. I've seen
this fault on similar models.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

In message .uk, Ed
Sirett writes
On Mon, 03 Apr 2006 23:03:11 +0100, Vortex wrote:

Hi There,

3 or 4 weeks ago my trusty 12 year old Prima 80F boiler stopped working. At
the time I gave it a (small well calibrated) thump. It started working
again and I thought no more of it.

Today it failed again. In the specific failure mode:

...The controls are calling for heat.
...The pump is running and the fan is on.
...The pilot light is lit
...but no main burner.

I took off the bottom cover and can see the gas valve is connected to the
electrical control PCB/gubbins by a 4 way MOLEX style connector.

* If I carefully wiggle this connector the main burner lights straight
away.
* If I turn down the temperature control it turns off the main burner as
you would expect.
* When I turn up the temperature the boiler *sometimes* returns to the
failure mode.

I sense a dodgy connection or a dry joint.

Q. Is this a common failure mode?
Is there a specific connector or component that is the most common
source of this problem.
The benefit of your experience is appreciated!

You've found the fault.
You might be able to make a repair with your soldering iron. I've seen
this fault on similar models.

I had a similar fault on a Potterton profile.

The pc board connector pins had dry/cracked solder joints. As someone
suggested, at the time, you need a magnifying glass to spot which pins
need re-soldering. Go easy on the heat applied as softening the plastic
part of the connector is very likely:-(

There was quite a long thread here last Christmas, but I think you
already have the conclusions.

regards



--
Tim Lamb

"Tim Lamb" wrote in message
...
In message .uk, Ed
Sirett writes
[snip]


You've found the fault.
You might be able to make a repair with your soldering iron. I've seen
this fault on similar models.

I had a similar fault on a Potterton profile.

The pc board connector pins had dry/cracked solder joints. As someone
suggested, at the time, you need a magnifying glass to spot which pins
need re-soldering. Go easy on the heat applied as softening the plastic
part of the connector is very likely:-(

There was quite a long thread here last Christmas, but I think you already
have the conclusions.

regards



--
Tim Lamb

Guys thanks for confirming my suspicions.

This morning I have unplugged and replugged all the connectors. Right now
"it just works".

If/when it fails again I'll rework the solder joints.


Thanks again,


David.

In message , Tim Lamb
writes


I sense a dodgy connection or a dry joint.

Q. Is this a common failure mode?
Is there a specific connector or component that is the most common
source of this problem.
The benefit of your experience is appreciated!

You've found the fault.
You might be able to make a repair with your soldering iron. I've seen
this fault on similar models.

I had a similar fault on a Potterton profile.

It's the same pcb



--
geoff

In message , vortex2
writes

Guys thanks for confirming my suspicions.

This morning I have unplugged and replugged all the connectors. Right now
"it just works".

If/when it fails again I'll rework the solder joints.

The answer is that it's bound sure to fail again

don't forget to check the loomside connector as well as the solder
joints
--
geoff