It sounds like the thermo-coupling is bad

 

I have a similar setup in my shop that I use to take the chill out. Mine takes several turns to get it to come on. The holding it down long doesn't work but repeated turns does. Push it in, turn it to the left and it will spark but not start. A few more times it will do this and then the flame will catch. I've found this is the only way around it for my unit anyhow. Hope this helps.

 

It's a thermocouple, the function of the thermocouple is to let the gas valve know that there is an actual flame(heat) so the valve doesn't stay open if there isn't(on lighting).

 

What makes the thermocouple quit working?

 

They just go bad/wear out. Some sooner than others. Cleaning the old one never helps and is a waste of time, but you should clean up the pilot assembly when you replace the thermocouple. That'll insure a good spark for ignition and a good flame covering the end of the thermocouple. A slightly longer thermocouple won't hurt anything if you can't find the exact length, but the longer the thermocouple the longer you'll have to hold down the button when lighting.

 

https://spaceheaterparts.com/product.sc?productId=1611

This appears to be the universal replacement for that type of heater. Looking at the pic there are terminals for a limit switch. You should also check to see if your thermocouple has terminals like this and a limit. They can go bad too. Easy to check with an electric meter to see if the limit is open or closed. It should be closed unless overheated. A bad limit would keep it from staying lit just like a bad thermocouple.

 

Thermocouples are ingenious little devices that are often used in applications like this. Basically they are two different types of metal connected together that produce a small amount of electricity when heated. To start your heater you push a button that opens a valve to allow the gas to flow. You ignite the gas with the sparker. In my experience it should only take a few seconds for the thermocouple to get hot enough to generate enough electricity to keep the valve open. If you have been holding the button for a minute to keep the heater running your thermocouple has been going bad for a long time.

 

Maintenance Man gives the straight scoop for this. One thing to insure before you declare the thermocouple deceased is to make sure the very tip of the TC is in the flame path. Only the tip of the TC is bimetallic, and a thermocouple will not work with heat along the length of it. Sometimes the things get bent up a little and don't heat up on the end.
Otherwise, thermocouples are cheap, as are tilt or limit switches, and they are not hard to replace. You should be back in business quickly.

 

Don't these heaters produce a lot of moisture as well?

 

Heck yeah! You can work up a sweat when it gets warm. In my uninsulated garage, that's rarely a problem, but I usually just make it warm enough to take off the chill and then turn it off.

 

Yeah, I had a bad experience with a kerosene heater and moisture. I need to upgrade my power so I can run a 220 heater. Until then I just have to bundle up

 

The burner may need cleaning. Mine acted like that and I took it apart and cleaned not just the thermocouple but the burner as well and it's been working fine again since (three years ago). I just used a wire brush to clean all the scale and rust and stuff off and made sure all the holes in the burner were clean and clear. When I put it back together I made sure the flame from the burner was aimed right at the tip of the thermocouple so that it got hot fast. Sometimes you get a bad bottle of propane that has more impurities than usual and they get left behind on your burner. I can't prove it but I think the gas you get in those "Exchange" programs where you trade your empty tank for a full one is less than clean. I stopped using them and haven't had a problem since.

 

A lot of good advice; let us know what solves the problem Quickstep.

 

Quickstep, I used to work in tool and equipment rentals, We rented all types of heaters which needed repairs and maintenance. We bought replacement parts from Portable Heater Parts. Here is the link. PHP | Portable Heater Parts - Your destination for all things heaters and rentals

 

Quickstep, I used to work in tool and equipment rentals, We rented all types of heaters which needed repairs and maintenance. We bought replacement parts from Portable Heater Parts. Here is the link. PHP | Portable Heater Parts - Your destination for all things heaters and rentals

Thanks for the info. Perhaps ironically, the heater I have I bought from a Rental Center. It was cheap and sure doesn't owe me anything, but it's handy to have and I'd like to get it going. I'm thinking about just replacing both the thermocouple and the limit switch. I found a parts breakdown online, but I haven't yet found a replacement limit switch that I know for sure is the right one. I'll check these guys out. Thanks for the lead.

 

Nothing's this easy, right?

I finally cracked this heater open this morning. As I began to remove the thermocouple to get a part number off of it, I noticed that out was unusually easy to turn the fitting that holds the thermocouple into the valve. So, instead of removing it, I tightened that fitting. I connected it up to the tank and it works!

Nothing's this easy, right?

 

Quickstep, A day without learning something new is a wasted day. I am glad you got it going. The way a thermocouple works is when the smaller than hair size wire that is inside the copper tube gets hot... it vibrates and induces a very small electrical current. The gas valve has a spring internally that holds the valve closed. When you push the pilot button on the valve, it allows a tiny amount of gas into the pilot and you light it. Once the pilot is lit... the heat from the pilot flame heats the thermocouple sending a current of electricity to an electromagnet that is energized, and that is how the gas valve is held open (by overpowering the spring). Once there is a continuous flow of electricity to the electromagnet in the valve... the gas valve remains on. After that you can turn the spigot on the gas valve which allows a second stream of gas routed to the burner. The thermocoupler has another external connection (on the thermocouple) that can be connected to a tip over switch, or a high temperature thermo disk, that can interrupt the electrical flow to the valve shutting the valve off by loosing magnetic power... then the spring in the valve shuts off the gas flow. That is how the system works.

 

Some units don't even have pilots. Mine doesn't. You turn on the gas, press a knob that opens the valve and hit the piezo button to fire it up, it gets full flame right away and after 5-10 seconds you can let go of the knob and it stays on. To turn it off you close the valve on the propane tank to cut off the gas.

 

Still works on the same principle... So does gas water heater, gas furnace, RV gas refrigerator... Gas valve held on by electricity provided by the thermcouple. The 5-10 seconds is how long it takes to generate enough power to overcome the spring tension in the gas valve.