Question about Heating & Cooling
I have a ruud deluxe 90 nat. gas unit built '87. The furnace turns on and the igniter glows, but won't light. The relay to the gas valve comes on about 15 to 20 sec. after igniter but I don't fell the gas valve open. I measured the voltage at valve and get .02V then 10.47 volts for a few sec then drops to .02V. ( From my vom meter I have to ground the red wire or I get a Neg. voltage reading. ??? )
I pulled the yellow wires off the circut board that come from the transformer and I don't get 24V or any voltage for that matter when 110v is on.
I don't think it's the valve because I can get it to open from the power of a 9V battery.
Is it a bad transformer or circut board problem or what?
First lets try the transformer. With your meter check for 24v on the output side. You cant check to ground on this, you have to check your meter with both wires to the transformer. If this is too complicated just try turning on the A/C, if it comes on, the transformer is good. The problem may be with the time delay relay. try by-passing it and then see what happens. since its an '87 when you say circuit board I assume its a board with all the low voltage wires attached to it right? Or does it have resistors, diodes, and relays molded into it?
Posted on Nov 04, 2007
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Posted on Jan 02, 2017
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Feb 01, 2018 | Ruud UAKA037 Air Conditioner
1. Thermostat calls for heat. 2. Draft inducer motor starts. 3. Pressure switch attached by a small plastic or rubber tube senses the negative pressure produced by the draft inducer and closes. 4. Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound. The ignitor did not glow, the flame sensor (a small metal probe about 1/8" in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops with no ignition of gas to heat your home. Your furnace shuts down and goes into a lock out condition until you turn your power switch back off and on again. Then the sequence starts all over again with no ignition of the gas. Solution: You probably need to purchase and install a new ignitor. I would suggest that you inspect your ignitor closely for cracks. Make sure you do not touch the ignitor with your bare hands. If you do not visually see a crack, then you could have a furnace control board problem or a limit, rollout switch problem. The furnace's control board might not be supplying the voltage to the ignitor. If your furnace lights and the gas stays on for 8 to 10 seconds, then shuts right back off, then you need to clean your flame sensor with light sand paper or steel wool. You might need a new flame sensor, but most of the time they can be cleaned an will work well after cleaning.
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