Hi Everyone, I have an 20+ year old American Standard Furnace. My pilot will not stay on at all. I have changed the thermocouple with no results. I also changed it again thinking I might have purchased a defective one. Still, not change. I have even checked all three with a volt meter and each checks out giving a reading of more than 30 millivolts. So if the orriginal thermocouple was always working what should I check next? I know that Gas Valves can be the problem also, but are there other and less expensive things that I should check or test first?

Also, I am pretty mechanically inclined and I am comfortable doing work myself. I'm good at making sure I do my due-dilligence before taking on new items to work on. By saying all of this I am asking whether it is worth it for me to tackle this gas valve myself. It looks very simple and cookie cutter to complete the procedure but do I need any special tools? Is it Illegal?

Thanks in advance...

Jermaine

Also, Is a gas valve servicable? If so what components should I bee looking for the clean, fix, or replace?

You need to clean the pilot lite orifice.

Thank you HVAC1000.. I already did that too. It has nice strong blue flame.

As soon as I let go of the red tab it goes right out.

Make sure thermocouple is in the flame properly. Gas valve not serviceable and must be replaced if necessary.

HVAC, thanks again but I thought about that too. It's getting a direct hit. I've even tested it with a volt meter while it was in the pilot. Gave a 31 -33 millivolt reading.

There are two wires that lead from it that goes to the other side of the furnace where all of the other electrical connections are. Could it be an electrical thing that might keep the Gas valve from opperating?

Yes it is possible a high limit control is attached to those wires.

Could it also be a culprit? Should I try to upload a pic.

Is there a test I can run? Or, is it's function function totally separated from the Pilot light function of the Gas valve?

If it is a limit it should show continunity on the ohm scale. In other words the circuit to that device should be closed.

If it is a limit it should show continunity on the ohm scale. In other words the circuit to that device should be closed.

Hvac1000 if I hook it up to a multimeter what should I be looking for? An ohm rating?? A volt rating or range?? Any insight would help.

Thanks

You can test the gas valve with a volt meter. The only problem is knowing witch wires to check at the gas valve. If you only have two it is simple, put a probe on each terminal and you should get 24 volts reading with the pilot lit and the thermostat way up and the heat/AC switch on heat.

If you have more that two wires then you have to find out if it is a redundant vavle or not.

Send a picture of your gas valve, so that we can see the wiring.

letmetellu thanks for responding. I will take a pic and post ASAP. I appreciate the help everyone.

It should show continunity or a closed circuit.

Hi Guys, here are some pics of my Gas Valve. They are the best but when I get home from work I will try to get some better pictures. I also sent the pic of the Black piece attached to the Valve that has the two wires and the electrical unit that they attach to on the other side of the furnace.

If you guys have any other advice to offer me please let me know. I am all ears...

Guys thank you for all of your help. I appreciate all the advice and insight you provided. The conclusion is the gas valve.

Whil I was doing to continuity test I found that all of the curcuits was closed except for the circuit inside of the thermocouple port. Because the circuit is open I decided to take off the front casing and that is where I found the tiny wire that connected to the back side had broken.

I could easily solder the connection reassemble the gas valve, but due to the pressures of the natural gas and not knowing if the reassembly would 100% leak free. I don't trust a 25 year old fasket nor do I think I can find another gaskest. Due to it being high pressure gas I don't think making a gasket would be a good idea.

Thanks again everybody, but I will change the unit even though I could have it relatively repaired in 10 minutes at not cost.