Mercury flame sensor trouble?


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Old 11-09-07, 01:17 PM
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Mercury flame sensor trouble?

I have a Weil-McLain HE 3 series boiler. The main burners will not light. The pilot light comes on after the fan is up to speed. But the pilot light flame does not seem to be big enough, or close enough to the flame sensor to trip it. The flame also seems to be caught in a draft.

I have followed the troubleshooting steps in the owners manual.

If I disconnect the flame sensor from the gas valve, the pilot light stays on. I then use a small section of wire to jump the connection on the gas valve, and the main burners will then come on.

I have tried replacing the flame sensor, thinking that it was not working. the boiler worked for 1 week, but now I once again have the same trouble again.

It seems like the pilot flame might be too small, is there a way make the flame bigger. There is a screw on the gas valve labled for an adjustment, but it does not seem to do anything. Can I maybe clean it somehow?

Any advice would be great.

Thanks,
 
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Old 11-09-07, 04:09 PM
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Originally Posted by mustangdan302
There is a screw on the gas valve labled for an adjustment, but it does not seem to do anything.
I would first try to clean the orifice. Then if I was satisfied it was indeed clean - THEN - I would try to adjust the pilot flame. Perhaps that screw you were trying to adjust was only a surface cap cover that hides the real adjustment screw that is down under it.

Also, see if the flame sensor is not able to pivot towards the flame better, somehow.

If you work on anything with the valve like this, first be sure to shut off electrical power to the boiler and also be prepared to shut off the vave that is in the gas supply line. Make sure this is able to work/turn, before doing any fiddling around on the gas valve!
 
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Old 11-10-07, 03:52 PM
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A little better

I have cleaned the pilot light, by blowing compresses air backward through the system. The flame is larger but still does not reach the flame sensor fully.

There does not seem to be a way to move them closer.

You were right about the adjuster being below the cover screw.

But the adjustment was already maxed out.

What would I do to upgrade the ignition system?

Thanks again.

Dan
 
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Old 11-10-07, 04:00 PM
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Sounds like a pressure problem then. Or perhaps the orifice hole is reduced in size and you just can't tell. Sure though you can't bend the hood or bend something over a bit to get them to touch (better)? I've done this a lot, successfully, with old gas water heaters where the pilot flame would want to draft upwards too much and miss the thermocouple.
 
 

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