Weil mclain boiler failed. It’s cold!

ripllewop

20yr old WM cg-6 series 12 boiler w/5 zones recently failed. Has new thermocouple, new rollout and spill switches... installed new taco pump months before failure...when calling for heat the damper rolls open, pump turns on, gas valve clicks once then again about 5-10 seconds later but doesn’t fire. Pilot stays lit(Propane fueled) 
notice 5A 240v fuse under wrap was blown but have read it’s supposed to be and not to replace. Hoping to find a solution short of replacing entire unit. 
Any help is appreciated. It’s the coldest week of the yr and can’t afford new boiler... 

ripllewop

Water pressure is good at 13-14psi...

Jamie Hall

You don't need a new boiler. You do need a good technician. Who will find out why the fuse blew, fix the problem, and get you on your way again. Have you checked "find a contractor" above? Or, if not, where are you located? We may know someone handy.

bucksnort

Sounds like you just need a new gas valve.

pecmsg

bucksnort said:

Sounds like you just need a new gas valve.

And what do you base that assumption on?

Alan (California Radiant) Forbes

Yes, gas valve or ignition control module (ICM). If you have 24 volts at the main valve connections on the boiler's gas valve, you need a new gas valve. If not, you'll want to replace the ICM.

bucksnort

pecmsg said:

bucksnort said:

Sounds like you just need a new gas valve.

And what do you base that assumption on?

I'd start there with a volt meter attached. If a constant 24V signal is present at the gas valve and gas isn't coming out . Maybe his propane line is froze up. Not enough info as to why a new spill switch or roll out switch was needed. Was anything diagnosed or just parts changed without a reason?

ripllewop

Replaced cheap parts to provide new safety devices that might fix the problem for less than the cost of a tech for an hour. Seems the right kind of gamble. New thermocouple seemed to slightly increase pilot flame intensity. 
Wire connectors and a couple screws are certainly within my ability level, as is some sweating, and tightening doped up pipes and fittings. Volt meter too. No spring chicken. 
Tank just filled but all other downstream appliances still working as usual. So I don’t think the line is frozen. 
Gathering and processing info from generous experts who like to help others may save me thousands if the tech who happens to be available were on the unscrupulous side of things during record cold. Better to be well informed if/when ‘visit from a tech’ time comes. 
Will check voltage next, as instructed. 
Thanks to all! 

ripllewop

Btw- it’s feeding 5 zones of radiant lines in slab... 

EBEBRATT-Ed

@ripllewop

Better off getting a tech than throwing parts at it

DZoro

Has new thermocouple, new rollout and spill switches... installed new taco pump months before
Many new parts there, rollout and spill switches are important safety devices and usually don't fail and do there job very well. Has the boiler been fully cleaned and flushed? Flue cleaned and open? 
Also is the new pump the same model as the original?
Really sounds like one of the safeties is tripped again....

bucksnort

Can you get a schematic ladder diagnostic troubleshooting diagram for your boiler? Start in the beginning and with a voltmeter you can determine what's good and move on to the next part. I'm guilty as hejj in changing good parts. Good luck.

SuperTech

It could quite a few things that are keeping the boiler from firing.  As others have stated checking voltage at the safety switches and gas valve is the best place to start.  It could even be an issue with the flue damper. If you are against calling a pro and are comfortable with using a meter to troubleshooting the boiler a flow chart is available online that can assist you in the process.