The heater will not fire. The pilot light is on (older heater) but the burner won't light, I jumped the gas block and still nothing, don't want to replace the gas block if it is something stupid. It has done this many times before then out of no where it will fire. Any suggestions?

Is the gas valve 24v or millivolt?

24 volt gas block with a standing pilot, I realized after the post you can't jump the block on a 24 v system like a mv.

http://www.robertshawtstats.com/spaw2/SiteContent/Training%20HEATING%20GAS%20VALVE%20SYSTEMS.pdf

You can peruse this PDF, and starting about page 32, go through the check procedure to see if the gas valve system has to be cleaned, adjusted, or replaced.

Do you have a manufacturer and model number for the gas valve? Maybe a more specific check procedure can be found.

http://www.robertshawtstats.com/spaw2/SiteContent/Training%20HEATING%20GAS%20VALVE%20SYSTEMS.pdf

You can peruse this PDF, and starting about page 32, go through the check procedure to see if the gas valve system has to be cleaned, adjusted, or replaced.

Do you have a manufacturer and model number for the gas valve? Maybe a more specific check procedure can be found.

Gas valve WR 36C21-411---Heater model 200-341... TY!

Thank for your patience. You can change the gas block for $160 bucks or less depending on where you get it from. That's better than taking it apart, and changing components. I can provide the rather detailed and extensive procedure for checking this unit with an ohm meter but may lead you to the same conclusion of changing the gas valve unit. I know, for that kind of money you can get a new heater for your garage/shop

http://www.northerntool.com/images/product/400x400/212/21273_400x400.jpg

Last question, is this a switch actuated or thermostat controlled heater?

Thank for your patience. You can change the gas block for $160 bucks or less depending on where you get it from. That's better than taking it apart, and changing components. I can provide the rather detailed and extensive procedure for checking this unit with an ohm meter but may lead you to the same conclusion of changing the gas valve unit. I know, for that kind of money you can get a new heater for your garage/shop

http://www.northerntool.com/images/product/400x400/212/21273_400x400.jpg

Last question, is this a switch actuated or thermostat controlled heater?
As you can imagine it is a very old unit, there is an electrical wall switch and a thermostat. Swapping out the gas block makes sense.

Before you go throwing parts at it, I suggest checking to see if you are getting 24v to the gas valve during a call for heat. If you are not, a new gas valve won't help a bit.

Before you go throwing parts at it, I suggest checking to see if you are getting 24v to the gas valve during a call for heat. If you are not, a new gas valve won't help a bit.
Thanks makes sense, but what get me is it is intermittent.

Presuming the thermostat is remotely mounted, try disconnecting it & jumpering the two wires together. Could be a stat problem.

Presuming the thermostat is remotely mounted, try disconnecting it & jumpering the two wires together. Could be a stat problem.
What is odd is that it goes through the firing sequence, once turned on the burner should fire but it does not. After about 45 seconds or so the fan turns on, I always thought the heat from the unit heating up turned on the fan, not the case, so it will blow cold air, when shutting off, it will go through the cool down cycle, letting the fan run for a bit...

On most heaters today, the fan is on a timer. X seconds after there is a call for heat, regardless if there is flame or not, the fan will come on & stay on until Y seconds after the call for heat ends. The fact the fan comes on tells me the furnace is getting the call for heat.

Ok, makes sense... just need some gas... TY!

You're welcome. When you get a call for heat, check for 24v between M & C or MV/PV & MV depending upon how your valve is marked. If you get the 24v, give the valve body a few firm raps with wrench or small hammer. Sometimes that will loosen a stuck valve.

You're welcome. When you get a call for heat, check for 24v between M & C or MV/PV & MV depending upon how your valve is marked. If you get the 24v, give the valve body a few firm raps with wrench or small hammer. Sometimes that will loosen a stuck valve.
LOL, first thing I did. I will put a test on it tomorrow.