I have a RUUD Achiever 90 Plus that won't light. The fan comes on, I can see and hear the igniter firing, but it doesn't light. I don't hear or smell any gas so I suspect that it is not getting gas for some reason. Any ideas would be welcome and thank you in advance.

 

There is no gas flowing from the "valve" to the burners.

 

Welcome to the forums.

Since the igniter is operating it means the safeties are ok. After the igniter is on for approx 30 seconds you should hear a click from the control module, which is the relay for the gas valve, and then burner should light. If it doesn't in five seconds the igniter will shut off and the system will retry and eventually abort.

You need to use an AC voltmeter to check for 24vac at the gas valve when you hear that click. If you don't have the voltage it's a wiring problem or the control module. Check at the multiconductor plug on the board. Try unplugging it a few times to remove any corrosion.

If this doesn't help you'll need to post the model number which can be found inside on the side wall by the burner.

 

Thanks. Will get on that. Further info... there is a plug in the line between the gas valve and the burners. I took this plug out and ran the start cycle to see if I could smell any gas coming out of the hole. There was none. I know gas is coming into the house since the furnace in our addition works. However, no gas is making it past the valve when the ignitor is active. So, I am pretty sure it is something to do with opening the valve.

PS
As mentioned, it does seem to run through 2 start cycles and then aborts.

Also, there are 3 vertical lights on the board. The lower 2 are green and are on. The top one looks like it is yellow or green and I have not seen it on. I don't know what these lights indicate yet. That is one of my next questions for Google!

 

That means you have gas in the house. There should still be at least one valve from the gas line to the non working furnace.

 

OK Update again. Had a little more time. System does try to light 4 times. It tries 2 times, then the main blower fan comes on for a couple minutes, it tries 2 more times and then goes into 1 hour lockout as indicated by the "OK" light on the circuit board. As I said, I know there is gas in the lines in the house since the other furnace works. However, gas is not getting past the valve in the furnace. I am looking for a diagram so I can check for the 24v at the furnace gas valve. There are 4 wires. I believe 2 are ground. Not sure what the other 2 are yet. I found a trouble shooting guide on the back of one of the doors but have to figure out how to "test" everything that the flow chart describes.

 

You can post pictures here so we can see what you see. http://www.doityourself.com/forum/el...-pictures.html

Big pictures are better. You can post them on a free picture site and link to them here.

FYI.... the yellow LED is flame presence. Is should glow pretty strong when flame is active. If it flickers you may need to clean the flame sensing rod. We'll worry about that later... that isn't your current problem.

There should be a union connecting your furnace to the gas line on the furnace side of the service valve. Turn the service valve off, loosen the union, crack the valve open and see if you get gas.

 

Problem found! Although I am not sure that it is fixed yet. Long story short... one of the pressure switches was not working. I don't know if the diaphragm was stuck or whether I just had a little corrosion on the electrical connection. I found the inop. switch by removing the 2 wires and jumping them... furnace lit. I then worked the diaphragm by blowing into the hose to try to loosen it if it was stuck. I then reconnected everything and the furnace worked. I did notice that one of the electrical connections may have had a little corrosion on it. So, now the furnace is working but I am not sure whether the diaphragm was stuck or a bad electrical connection was the culprit. Either way, it is fixed until it breaks again. Only then I will have a good idea where to start. In the meantime I will track down a new switch just in case it quits again.

Thanks for all the help and have a great week.

 

That doesn't make any sense. The igniter WILL NOT start to heat up unless the pressure switch is satisfied. If the pressure switch was the original problem.... the igniter would never have heated up.

 

The igniter is not a glow plug type but rather an electronic "spark" igniter similar to what's on a gas grill which is probably irrelevant. However, there are 2 pressure switches on my furnace. I believe one is for the condensate drain and the other for the exhaust fan. I believe the bad one was for the drain as the fans all seemed to be working. I have read that if the drain switch is inop. the gas valve will not open which was the case here. When I jumped the wires to the switch, I could then hear the gas valve open. Prior to that I heard nothing.

 

Ok. I'm helping so many members it's hard to keep them straight. I should have asked for a model number originally.

 

No worries. I don't claim to understand how everything in there works. I'm just reporting what I did to get it going again. As I said, I am pretty sure it has something to do with that pressure switch. Whether it is a bad switch or just a bad connection remains to be seen.

 

This was very helpful to me. It made me realize step 1 was to make sure the gas line was turned on. It was not. When I had a gas smell last summer, a technician came out and checked both water heaters and both furnaces, and he must have left the gas valve shut on the number 2 furnace, because that was the only problem. Thanks for taking me through the steps.

 

... I had the same problem. I read this thread blew out and sucked in on the the vacuum actuator valves. My heater boom my heater lit up. Thank yso uch

 

Welcome to the forums.

That's a pressure sensor and easily damaged by blowing in on it. The switch itself doesn't typically go bad.... it's the vacuum line connection to it. Remove the hose and make sure it's completely clean. Then clean the orifice inside the nipple on the inducer blower where the hose connects. The little tiny hole you need to clean is down inside the fitting. Use a small piece of wire, pin, small drill bit to clean it out.