The following is a reprint from our Ask the Expert feature on AcmeHowTo.com

Question: Hi there, I have an older White Westinghouse gas dryer, that lately isn't putting out much heat. I ran through your troubleshooting articles, and everything is functioning normally, except that the flame tube has a deposit of soot and the flame itself is mostly yellow. I can't reach in there effectively to clean it out... What do I do now?

If it makes any difference, our gas refrigerator has been having soot trouble lately as well, we were wondering if we have a bad batch of propane.

Thanks for your help

Answer: The build up of soot suggests a problem. Gas is a clean burning fuel that only leaves a residue if it doesn't burn completely, and that would typically be because of impurities. So a bad batch of propane is conceivably a possibility, although I can't say I've run into such a problem. However, in my area we don't use propane. I'm familiar with natural gas. I do know that if you run gas appliances on propane, you need a special fitting for the alternate gas. Since the dryer was working before, I'll assume the appropriate fittings have been used.

I believe that a blue flame is expected with propane, just like with natural gas. The reason that you might get a yellow flame is a gas jet that is not clean, or an air mixture problem. The air mixture usually would result from the adjustment (if any) on the venturi tube (the tube that the flame is housed in). If there is a sliding door on the tube, then you can try opening or closing it a little at a time to try and improve the air mixture. However, since it worked before, the door seems less likely to be the problem.

If you can get a toothbrush (dry and no toothpaste) into brush the tip of the gas jet, that would be a good place to start. Another thing to try, if possible, is to connect up a small propane canister to the dryer. Use of an alternate propane will help to test the "bad batch" theory. Note that it might not show an instant improvement, it may take a while. You could just call the propane dealer and ask if anyone has reported similar problems.

I know you read through the instructions on the website, but just in case you missed this point, here it is again. The most common cause of the problem you describe is a restriction in the airway in the dryer. It can occur anywhere from the blower wheel, through the vents in the drum, out to vent opening, the vent hose to the exterior vent. Making sure that the entire pathway is clean and there are no kinks in the vent hose will often resolve the problem you describe.