I've got a Williams gas wall heater that won't fire up. It was working fine (it's about 8 years old) until last weekend then stopped.

The pilot stays lit but when I turn the thermostat up nothing happens. I tried adjusting the thermostat (it's a millivolt type), then replaced the thermostat, and still nothing. Also checked all the connections and the pilot and they seem fine.

Any advice on what to try next? Would a bad thermocouple show these symptoms? I hate to blow $175 on a new gas control valve (they're non-returnable out my way) if it's something simple.

Thanks very much for any help.

 

First thng is to clean the pilot. Especially if it has the low voltage type (250mv) Just a little lint will mess things up. After that if it still is a no-go jump the thermostat wires.
My money goes to a dirty pilot.

 

Thanks for the suggestion, mbk3. I'll give it a shot tomorrow.

 

Well, I removed the pilot and it was dirty, so I blew compressed air through it. Reinstalled and now it seems too clean: the gas just streams out the pilot now.

When I light it it looks like a little blowtorch with a wide flame. Did I blow something out of the pilot? I unscrewed the part on the bottom end with the tiny pinpoint orifice and also blew air through that- maybe that did something?

The good news is that the heater fires up with the blowtorch pilot, so at least it's not the gas control valve.

Thanks again for the help.

 

You may try reducing the pilot thru the pilot adjustment on the gas valve

 

Thanks for staying with this thread.

I adjusted the screw but it only made a marginal difference. So I picked up a new pilot generator assembly (Lasco 36-0681) and it's the same-- the flame seems to be shooting with too much intensity out of the pilot.

Called Lasco and the tech said that it's standard for the flame to shoot out in this way, and that the flame may even extend 1" past the thermocouple. I've never seen any heater pilot flame look like this, but who knows-- maybe I'm so used to old and dirty pilots restricting the flame in some way that a clean one seems "wrong."

Thanks again for your comments.

 

We have a similar situation. It is a Williams Wall Heater that will not stay lit. We do not know how long it has not been operational, as it is a rental house, so it could have been 3 years (the tenant said a space heater was cheaper to run). If the thermostat wires are disconnected, the pilot will not light. If the thermostat wires are connected, the pilot will only light if the thermostat is calling for heat. If the thermostat is calling for heat the burner lights, but when we turned the thermostat to not calling for heat, the burner stays on. The only way we could turn with buner off, was at the heater valve or by disconnecting the thermostat. Then the pilot went out, too. We have replaced the thermostat (MV) and we have tried replacing the thermocoupler. But neither of these two things changed the pilot operation. We also checked the MV and it should be 450, but is less. We called the gas company, who's rep looked at the heater and said it was not generating enough power and that a $40 part should fix it. Since we have already changed the thermocoupler and a new valve is about $200...what are we missing??? Thanks in advance to anyone who has suggestions.

 

I suggest you call the gas co back. Ask them to write down the millivolt reads.

A-Across the generator terminals
B-Across the operator terminals
C-Across the thermostat terminals

All reads must be taken with the thermostat calling for heat.

 

Could this issue (pilot flame too intense-- it looks and sounds like a blowtorch) be caused by the gas valve? Is there anything else I should check before forking out the dough for a new valve?

Just to recap:

1. The heater was working fine.
2. The heater stopped firing up when the thermostat was turned up (the pilot was fine).
3. Cleaned the pilot with compressed air.
4. The heater fired up but the pilot flame seems way too intense.
5. Adjusted the pilot screw which made only a slight difference.
6. Replaced the pilot/thermocouple assembly.
7. Same problem with intense pilot flame.
8. ???

Thanks again.

 

There is always the chance of an over pressure situation, however it happens rarely. Why don't you have the gas co come by and check.

 

Thanks for the suggestion, mbk3. I'll make an appointment.

 

So the utility co. tech came by and guess what-- the "blowtorch" pliot is fine! He said that the new pilot generators (he referred to them as Target type) are meant to have much stronger pilot flames so as to prevent them from going out.

I was stunned. It's MUCH noisier than the old one, and it makes me wonder how much more gas they burn in pilot mode (the tech said it's negligible, but I wonder).

Learn something new every day. Thanks again mbk3.

 

I'm not sure why your pilot adjustment screw will not allow you to turn off the pilot if you wanted to, let's say.

Never heard of any heating device requiring or being normal to have blowtorch-like pilot. Even though tech gave opinion, there are many techs in this world, and not all agree or have the same knowledge.

 

Good points ecman51- thanks for the feedback. The tech was not the only one to say the more intense flame was okay-- the rep at Lasco said the same thing. But I agree that it would be nice to have further verification.

As for the pilot adjustment screw, I've never seen any work that well, and none that would completely shut off the pilot. There are a lot of these old heaters in my area, with Robert Shaw gas valves, so I'm kind of familiar with them, but again, I'd love to hear from people with more experience and knowledge.

It's this type of pilot generator:

750 Millivolt Pilot Generator Universal Pilot (L.P. Gas or Natural Gas) (Right Pilot) (Robertshaw): American HVAC Parts

 

You should be able to throttle that down a bit. Being careful to keep plenty of flame on the generator. You statement about never seeing a pilot adjustment that worked kind of threw me. I have worked on many thousands of furnaces over my career and have found only a few that would not adjust. Are you turning the adjust screw the right way?

 

Well I've always turned the screw clockwise to adjust it down, and have seen small changes, but never anything dramatic. Maybe I'm doing something wrong.

 

Nah your doing it right, maybe give it a little more umph. lol

 

Ha-- sounds good. I've also got a sledgehammer, so maybe a light tap here and there...