OT heater gas valve

The gas valve on the propane heater is acting up. The pilot won't stay lit when I let up on the pilot bypass, meaning, I press down on the bypass to light the pilot and after the thermocouple is warmed I let up and the pilot is supposed to stay lit. The pilot goes out when I let up. I replaced the thermocouple and the pilot still goes out. The pilot flame does heat the thermocouple tip enough to make it red so I assume the thermocouple is heated enough to make it work. Next step is to replace the valve unit. It's a Robertshaw but some of the tag is missing so I can not get a clear model number off of it. It has a capillary tube type thermostat heat sensing unit, not a remote thermostat.

I need some advice from you guys who work with gas, is there a way to repair the valve or do I get a new one? I looked up Robertshaw valves on the net and ended up with pictures of valves that might work but I don't know enough about this to trust myself with ordering one that might fit.

The inlet port is 1/2"NPT and the outlet port is 3/8" NPT. BTU's of this unit is 52000.

Can any of you decipher what I do have going by the picture? Thanks.

Pictures will be in the next post. I have been having an awful time getting pics to transfer from the phone to the computer so I have to post them straight from the phone. GRRRR! Thanks Windows 10!!!!!

Pics.

I have had some success cleaning the pilot orifice and adjusting the pilot flow valve.

Take the pilot assembly of the tube, look inside where the line attaches, there should be a jet inside. The hole will be so tiny it is nearly invisible. Clean it with carb cleaner and compressed air. Don't try to poke anything through it, just try blowing backward through it.

Before reconnecting the line to the pilot assembly, carefully try lighting the open line. If you get a good flame, the restriction is in the pilot assy itself. If not, on the valve there should be a pan head screw near where the pilot line attaches. Under the screw is an adjustment screw. Try backing the screw out a few turns. If you still can't get a good flame, the valve will need to come aoart and be cleaned, or replaced.

The valves are mostly universal. Just be sure it is for propane, the BTU rating is the same or greater than the original, and the control voltage is the same.

I forgot to mention I have cleaned the orifice several times with carb cleaner and compressed air. It appears to be OK through a magnifying glass. The carb cleaner shoots through it with an acceptable spray strength. I have played with the pilot gas pressure on another heater in the past and I burned up a thermocouple from too strong a flame. The end of the thermocouple on this one does get red in fairly short order. This is not a major brand heater so there are no dealers in the area. We heat the house with it.

Oh, I did mention the thermostat is in the valve and is controlled by a capillary tube coming out of the gas valve. I have had thoughts of getting a valve that utilizes an external thermostat on the wall. This would be my chance to make the change if I want to but this arrangement works OK so I am reluctant to change something that works.

If it gets the thermocoupler red hot, it has plenty of heat.

Sounds like something is wrong inside the valve.

I doubt you will find one with that type control. Probably going to have to update to 24 volt, which will mean adding a transformer, or go with line voltage. Either way it will need a power source.

How old is the heater? If it's getting some years on it, the heat exchanger may be getting thin. Do you want to invest in fixing it, or put that money toward a new one?

(quoted from post at 10:24:44 10/11/17) If it gets the thermocoupler red hot, it has plenty of heat.

Sounds like something is wrong inside the valve.

I doubt you will find one with that type control. Probably going to have to update to 24 volt, which will mean adding a transformer, or go with line voltage. Either way it will need a power source.

How old is the heater? If it's getting some years on it, the heat exchanger may be getting thin. Do you want to invest in fixing it, or put that money toward a new one?

Click to expand...

The heater is ten years old or less. On the website I lresearched they do show this valve with the capillary tube.

This heater has a control knob on top of the heater connected to a rod that goes down to the control valve. You can see it going up from the top left side of the valve in the picture. The valves I see have a turn knob on the control valve where this tor connect on mine. I don't know if I could pull that knob off and transfer the linkage off of the old valve or not.

The oil heater that used to sit where this heater is had a wall thermostat when I was a little kid back in the fifties but something went wrong with it and we ran the heater manually after that.

Check for recalls on that gas valve and you may get one for free. Some valves have been recalled as they leaked.

We have a gas heater in the deer shack with a control like that. Must be over 40 years old or more. When the control failed I took it to the gas supplier & he found the right one for it.

Don't be afraid to try one more thermocouple, You can get a bad one.

The thermocouple in this picture is not new

The thermocouple in the picture is the old one I put back in after the new one didn't work. I thought I would give it another try. I will try another new one first before I replace the valve. After dealing with new vehicle electrical parts that don't work it wouldn't surprise me if thermocouples are in the same category.

First off, remove the pilot tubing from the valve and
at the pilot head at the thermocouple, clean tubing
good and check the oriface at end if tubing for
buildup , after reassembly and still not staying lit
double check flame contact at thermocouple, also
make sure you have thermocouple snugged up tight
at valve, if still not working and you have copper
tubing running up to the valve then remove tubing at
both ends hand shake and bump it against
something solid, ive seen copper scale up internally
and stop the valves up, if still not working holler
back

Looks and sounds like the same valve we put in Trojan brand stock tank heaters. Even thouh we were original equipmemt manufacturers, (oem) Robertshaw would not sell us parts. We had to turn them in for warranty if new enough or tell customer tough luck if it was out of warranty.

My shop hanging heater had the buildup in the pilot orifice...cleaned it and all was good.

that is not the thermocouple. It is the capillary tube for the bulb temperature sensor.

that is a plain ole Robertshaw 700 series. Same basic body will accept several different operators. The safety magnet is replaceable if you can find someone who has
been in the heating business for a few years.

Make sure the place where the thermocouple screws in is clean. it doesn't take much to make it lose contact.

Thanks Russel that's good to know. There are a lot of 700 series valves on the websites only in different sizes. Now another question. This new thermocouple I have states it's for 24 volt or higher systems. This thing does not have any electricity going to the valve body, does that make a difference.