Diagnosing bad pilot light in B-W gas water heater

Jells

Hi,

I've got a 5 year old 75gal B-W NG (M-I-75S6BN) water heater that won't sustain a flame, it goes out when I release the button. I replaced the entire pilot unit ($28) which includes both the thermocouple and the pilot, but no go. I thought I'd ask here before going in for $200 and replacing the control valve. Is there something I'm missing? Or are those electronic controls more failure prone than the old school valves?

Tim McElwain

Can you get a picture of the valve and some control numbers? Have you taken any millivolt readings?

Jells

Tim McElwain said:

Can you get a picture of the valve and some control numbers? Have you taken any millivolt readings?

I don't think standard thermocouple mv readings help with this one, it uses a special one that generates the voltage used by the electronics. Besides, I already replaced it.

SKU:239-48275-01Brand: Bradford White

Tim McElwain

That is a WV model from Honeywell. It uses a pilot generator putting out 750 millivolts to power the electronic board with the 750 millivolts DC. I have the troubleshooting procedure for it send me an e-mail at gastc@cox.net and I will get it off to you.

Jells

That's very generous of you Tim! But can I ask, as I'm trying to get this back up ASAP to provide hot water for a tenant (currently marginal using boiler heat exchanger), what are the repair possibilities if the pilot assembly is new but still no sustainable pilot light? I had not thought the valve control unit was serviceable, just replaceable.

Tim McElwain

What Status Light indicators are you getting? What is the Honeywell number on the control it should be WV with numbers following. I can take the time here to go through the 30 or 40 pages of diagnostics with you or as it seems you want to just go ahead and change the control. Your choice? An electronic failure would be indicated by 7 flashes on the light on the control.

Jells

I don't want you to spend a lot of time, I'd be happy to go through the process with your materials, but is the control valve actually serviceable, or is replacement really the only option whatever the cause? I'm just not seeing where there's an alternative to control valve replacement, if I've already replaced the pilot assembly with no change of symptom. At one point it was giving the 2 flash 3 second interval of low pilot. The simple diagnostic on their website said replacement.

Tim McElwain

What is it giving now since you replaced the pilot? The procedures that they give to service this unit also cover other attachments to the control. I do not have the exact spec sheet on the model you have but the procedures that Bradford White gives for all their water heaters with this control system. What other features does this heater have, does it have the "Icon System" for example?

Top answer your question the printed circuit board is not serviceable so it would mean replacing the entire control. The truth is these controls have been pretty reliable.

Jells

I was back at the property today, the valve is WV 88600 1010. I saw nothing to indicate any "ICON" system. When I try and light it, the led does the 3 second "all is well" while I hold the button, then goes to nothing within a short time after I let go, presumably after it's capacitor is discharged.

So, do understand you correctly that you agree with me since the problem isn't in the pilot unit (replaced and gives a healthy flame), it has to be in the control valve, and since the CV isn't serviceable, I need to replace it no matter what? I haven't heard another possibility.

Tim McElwain

If the pilot generator is putting out 750 millivolts and the unit will not stay on then try replacing it just don't throw the one you remove away.

unclejohn

$28.00 bucks for the whole assembly? Are you sure you got the right one?

Jells

unclejohn said:

$28.00 bucks for the whole assembly? Are you sure you got the right one?

Yup, it was identical. Seemed like a deal, but it was at a pretty good pro supplier. The little "bodega" plumbing supply wanted $58 just for a non-oem generator that didn't have the right connectors. I ordered the control this morning, it seem from some pictures not from that supplier that it comes with the pilot assembly too. Bummer. I guess I'll now have a backup.

Jells

Followup: replaced the control and everything has been fine.