Luxaire Furnace Blowing Cold - 8 Red LED Flashes

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Old 03-01-10, 08:00 PM
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Luxaire Furnace Blowing Cold - 8 Red LED Flashes

We have a Luxaire furnace that has been giving us trouble over the past year. It was heating the house up one degree and then clicking off. The only way to get it to come back on was to turn the thermostat off & then back on.

Recently, it started blowing cool air.

Today, we replaced the hot surface ignitor. It glows red, lights the furnace and then the flame goes out quickly (like within 5-10 seconds). We then cleaned the flame sensor and tried again. Same thing.

We checked the pressure switch voltage and it's good.

Now we're getting 8 red flashes on the LED indicator, which means "IGNITION LOCKOUT DUE TO RECYCLES".

Any ideas what step to take next? We're cold!
 
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Old 03-01-10, 08:53 PM
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I see NATE in your ID.

Can you measure flame rectification and verify a good ground to the furnace and to the control board?

Reset power and watch it try to start. Does it display an error code before locking out and giving you the IGNITION LOCKOUT DUE TO RECYCLES code?
 
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Old 03-02-10, 09:18 AM
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Thanks for your response, Houston.

I'm not for sure how to measure the flame rectification.

As far as operation, the system shows a slow green light which seems to be the normal code.

The system appears to light when the initial call for heat comes in, however, the flame is only lit for approx 5 secs and it shuts off. The system light turns to amber which appears to be normal from what I have read.

However, it goes through the gas lighting phases 4 or 5 times and then it goes off and flashes 8 times.

I'm no expert at this, so if I need to call in a tech, please let me know that as well. I was hoping to see if it was something simple.

Thanks,
Nathan
 
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Old 03-02-10, 01:38 PM
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clean the flame sensor, it will be a rod immersed in the flame. thats what it sounds like, and ur other problem about it going up one degree sounds like ur limit switch is shutting off the gas because it is too hot.
 
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Old 03-02-10, 01:46 PM
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I cleaned the flame sensor last night.

The serviceman just left. He tested EVERYTHING. Looks like we need a new pressure switch. He was great. Told us where to get one (he even called around & found one) and how to change it out.

Thanks!
 
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Old 03-02-10, 03:24 PM
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interesting, given that problem i never would have guessed pressure switch. mostly because the pressure switch is activated before the flames come on.
 
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Old 03-02-10, 04:45 PM
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But he also said the flame goes out.

A marginal pressure switch, or marginal fault in the venting of the furnace could cause such behavior. Not sure how the tech came to the conclusion it is the switch though. Nate said that the pressure switch voltage said good, but did not expound on when the test to it's 2 or 3 terminals was taken.
 
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Old 03-04-10, 06:34 AM
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Well, it's not the pressure switch. I changed it out yesterday. Now the flame stays on & the furnace started blowing warm air.

But it still locks out. Still getting the same 8 red flashes (lockout due to recycles). We had it on yesterday evening & it seemed to be working fine. I didn't go stand in front of the unit b/c it appeared to be working. We set the thermostat (which the tech also bypassed yesterday to make sure it wasn't bad) & went to bed. My wife heard the unit come on once during the night and then again this morning. I'm guessing that was it resetting after locking out.

You can turn the unit off & back on to override the lockout (otherwise it tries again in an hour?), but it works for a few minutes & locks out again.
 
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Old 03-04-10, 07:53 AM
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Why did you change out the pressure switch? Did a voltmeterr test show that current was not passing through it? Even if there is not, more often than not it is because of something obstructing how the furnace can draft. That is why there is a pressure switch in the first place - so the outgoing electrical terminal can shut off, for safety reasons.

You need to let us know if you are losing power off any of the terminals of the pressure switch, when the flame goes out.
 
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Old 03-04-10, 08:11 AM
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The technician who came yesterday tested everything he could. He checked for birds' nests, tested the flame sensor, bypassed the thermostat, etc.

He got an error (6 red flashes) that means the pressure switch opened 4 times during the call for heat. (I guess I didn't mention that previously). Then after a while, it gave him the 8 flashes for lockout.

So, before, the furnace would come on, blow warm air, but click off before heating the house to temp. Apparently it was locking out (we didn't know about the LED indicator at the time, so never checked it). The only way to get the furnace to come back on is to turn it off or back on (or wait an hour for it to attempt to heat again).

Then it started blowing cold air. The furnace would come on, the ignitor would glow hot, the flame would light but go out quicly.

Once we replaced the pressure switch, the furnace will stay lit. But it's doing the same thing it used to do. It'll come one, blow warm air, but it clicks off (lockout) before heating the house to temp.

Could it be overheating? A gas valve? A relay switch?

ETA: When I tested the voltage on the old pressure switch, it was 24.
 
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Old 03-04-10, 09:11 AM
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Originally Posted by natedog51 View Post
ETA: When I tested the voltage on the old pressure switch, it was 24.
If you test across the two terminals, when inducer fan is running, and get 24 volts, then switch is open (not passing current). [But how can that be?: That it says 24 volts, yet is open? Answer: It has to do with resistance and the easiest path current can take. Your meter is a resistor. If say the PS was "closed" instead, the easiest path to ground for the 24 volts is through the PS, because that is only a switch, and not a resistor, like your meter is. Therefore the reading on the meter would be an infinite...same as 'open' read, where the meter acts like it was never even hooked up. But when the reading, with such a testing method(called "in series" testing) is 24 volts, the pressure switch is "open", and the only path it can take to ground is through your meter.]

To sum up the paragraph above: Readings will be the reverse of what a layperson's logic might think.

But if you test from one PS terminal to ground (I prefer this method as it is most logical to understand for anyone) and it is 24 volts, and test the other PS terminal to ground, and only one terminal yields the 24 volts, then once again, the PS is "open"(not passing current, for given reasons in my other post). BUT, If doing same test you get 24 volts to ground off each terminal, the pressure switch AND drafting and all safety functions of the 24 volt circuit of the furnace is good. And the burner should stay on, unless something ELSE is wrong, instead.

You want ot catch this in the act with meter attached at the pressure switch's outgoing wire/terminal -------> ground. IF the flame goes out and yet you still show current, then test voltage at gas valve, to see if that stays on or goes out. If that too shuts off 24 volts (more than likely), then unplug and replug jacks and spade connectors, especially those dealing with the circuit from board to gas valve.

If none of this is it, it is likely the control board.

Is the furnace tech so puzzled that he cannot solve?, or don't you want to pay him for another service charge?
 
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Old 03-04-10, 09:40 AM
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He was puzzled by the entire situation. He said he wouldn't have guessed it was the pressure switch, but it appeared that's what it was. And it did solve the flame-no-staying-lit problem. But it appears as if there is more to it than that. He was convinced that the entire problem was the pressure switch, and if not, the control board. He never mentioned a potential problem with the gas pressure.
 
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Old 03-04-10, 10:47 AM
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Well, by also testing voltage at the gas valve, then one can know if power is remaining at the gas valve or not. If it is, then the gas valve would be faulty. If the 24 volt power does not remain at the gas valve, while there still is a confirmed call for heat going on (and you need to verify that), then something other than the gas valve is at fault. And about all that is left is connections or the control board itself.

After the advice given so far, what do you plan to look at now?
 
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Old 03-04-10, 11:04 AM
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Originally Posted by natedog51 View Post
He was puzzled by the entire situation. He said he wouldn't have guessed it was the pressure switch, but it appeared that's what it was. And it did solve the flame-no-staying-lit problem. But it appears as if there is more to it than that. He was convinced that the entire problem was the pressure switch, and if not, the control board. He never mentioned a potential problem with the gas pressure.

It's quite common for pressure problems to be right on the edge of the margin for the pressure switch to close. In such cases, replacing the pressure switch might cause the furnace to start operating some of the time, or to improve somewhat. But an underlying problem often causes the equipment to again start operating erratically.

About 5% of the time a bad pressure switch causes the pressure switch to fail to close. 95% of the time it's a problem in the furnace or venting system.

Despite this, people and even repairmen go for replacing pressure switches like a duck on a junebug.

Suppose a pressure switch costs $60. You have to replace $1200 worth of pressure switches to find one that was actually bad. In my opinion, that's an expensive part!


Yet people keep changing them out....
 
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Old 03-23-10, 11:22 AM
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I have a luxaire 9c series furance. it was installed 10/09. last my month my furance was not working properly and gave me 6 blinking red lights. After doing research online i decide to take the small hose that connects to the pressure switch completly off and blow it out with air. A small piece of dirt fell out , and I reattached the hose back. NO broblems ever since. Before you call an hvac guy and spent a lot of money, try blowing out the tube. You never know it might work. i can provide pictures if you want.
 
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Old 03-23-10, 11:38 AM
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I have a luxaire 9c series furance. it was installed 10/09. last my month my furance was not working properly and gave me 6 blinking red lights. After doing research online i decide to take the small hose that connects to the pressure switch completly off and blow it out with air. A small piece of dirt fell out , and I reattached the hose back. NO broblems ever since. Before you call an hvac guy and spent a lot of money, try blowing out the tube. You never know it might work. i can provide pictures if you want.
 
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