Intermittent Gas Valve Problems (Carrier LP Heating Unit)
All – I have an older Carrier LP heating system that began having intermitting problems about a year ago. I had a HVAC pro diagnose the problem. He told me that they main board, lockout timer, and airflow switch were bad. Given that I am a die-hard DIYer, I replaced all components myself. After replacing the three parts, the blower would kick on but no ignition. I called the pro back out and he found sludge in the tube on the output of the airflow switch. Once he cleaned that, all ignited and the system fired up beautifully. The only problem was that the flames would fire and intermittently sputter, if you will. It was like someone was shutting the gas valve on and off every couple of seconds. We let the system run for a few minutes to be sure no air was in the main line as I had the propane company service the main lines a couple days prior. The tech tested the gas pressure before and after the main gas valve (current part #EF32CW184A – modified for LP). The pressure after the valve was intermitting while the pressure before the valve was constant. This would make one assume that it is, in fact, the main gas valve sticking or something. Given that I have already thrown three expensive parts at the unit and now a fourth, I am looking for some added reassurance that this may be the problem. My question to all is – What are the possible symptoms of a bad gas valve? Is it possible to produce intermittent gas pressure as apposed to all-or-none? Is there anything else I should investigate? Lastly, the new replacement part for older model EF32CW184A is EF EF32CW183. Given that my part was modified for LP, is the new 183 part already modified or how is the modification identified? Thanks in advance for your help! It is about 60 degrees today as apposed to the 20s/30s. I just fired the system up to see what would happen since the temps warmed up. The gas seems to be flowing fine now without interruption. Might my problem be temperature related? The early diagnosis of the intermitting system failure seemed to happen only during rapid temperature drops. My unit is in my basement. Some other threads discussed electronic issues during temperature shifts. Is it possible that the valve can stick as well during colder temps? I came back in this afternoon to find the gas flow intermitting again. System cycles on just fine but flames stop and start about every 3 seconds. Can anyone please help me identify the problem? Thanks. I would not condemn the gas valve until you rule out that current to the gas valve is not fluttering from some marginal safety circuit issue. Originally Posted by vtbeachnut The tech tested the gas pressure before and after the main gas valve (current part #EF32CW184A – modified for LP). The pressure after the valve was intermitting while the pressure before the valve was constant. This would make one assume that it is, in fact, the main gas valve sticking or something. Heaven forfend --- a repairman WITH a manometer who USES it! So what did this repairman conclude from his observation? Ecman makes a useful point that it would be worthwhile verifying that the voltage on the gas valve was sufficient to cause reliable operation while it in fact was producing unreliable operation. In general I would expect a repairman using a manometer to be skilled enough to check such things if he thought it worthwhile, but you never know, I suppose. Did this person leave you a written notice on what he found? If so, what does it say? You describe the affect as being intermitting, but I don't know what that means---- was it varying or shutting on and off? Or what? One useful diagnostic technique considers parts as being black boxes. If all the required inputs are present, then a predicted output should be present. If it's not, the black box is defective and should be replaced. The test done with the manometer presumably found all the inputs in place, but got the erratic gas pressure as an output, which should not have happened. Most main burner gas controls have pressure regulators as a part of them, and while I've never seen this kind of erratic performance from a gas valve wouldn't hesitate to replace it if I did. In short, it sounds to me like your repairman did a competent job for you. If he recommended changing out the valve, I'd be inclined to do it. Thanks for your replies guys. The repairman did use a pressure meter to test gas pressure both before the gas valve and then after the gas valve. The pressure before the valve was constant while the pressure after the valve would hold normal pressure for approximately three-second intervals with interrupted pressure in-between. It is like water flowing through a hose and doing a pinch-and-release. It is only a split second that the pressure drops. The gas pressure is a follows – 3Sec on / quick interruption / 3Sec on / quick interruption / 3Sec on / quick interruption… In addition to testing the pressure, he did test the voltage and confirmed that all was consistent to the device. Can failure of a gas valve cause such consistent symptoms? I can't recall seeing the problem you describe, and I can't really think of how the gas valve might cause such a problem other than a defect with the pressure regulator that might be causing erratic operation. But there the problem is, nonetheless. And since the voltage is remaining on at proper levels while this problem is happening, there's every reason to blame the valve and replace it. It sounds like your repairman has done a very good job of diagnosing a problem for you. My understanding is Carrier has some LP units that operate at 3.5wc instead of the 11wc we are used to. I would be curious to know what pressure reads were obtained. Also did the meter used have the ability to pick up the reads within the 3 second fail time. Another thought: does this use a 3 wire pilot or a hot surface igniter for ignition? A 3 wire pilot could be presenting the senario you describe. Interesting points, mbk. The report we were given did say that the repairman found the voltage supply to the gas valve remained steady while the gas pressure output varied erratically. This was in the post at 7:53 AM. Nevertheless, perhaps beachnut can give us the model number of the furnace obatined from the rating plate in the burner compartment and the burner manifold pressure if that was given by the repairman doing the pressure tests. Originally Posted by SeattlePioneer Interesting points, mbk. The report we were given did say that the repairman found the voltage supply to the gas valve remained steady while the gas pressure output varied erratically. This was in the post at 7:53 AM. Nevertheless, perhaps beachnut can give us the model number of the furnace obatined from the rating plate in the burner compartment and the burner manifold pressure if that was given by the repairman doing the pressure tests. I realize the voltage appeared to show steady, but we had some meters at work that had a lag time between reads, sometimes made it difficullt . Just a thought And that is why it is nice to have an analog meter also. I have seen gas valve readings on my digital jump(flutter is more like the word) to all kinds of numbers when the gas valve opens. I would think that a repairman who is checking the burner manifold pressure and the gas valve voltage would be looking at that issue pretty carefully. And a Carrier three wire pilot that is turning the burner on and off repeatedly usually has the gas valve solenoid clicking on and off rather noisily. The absence of additional information from the repairman continues to lead me to suspect some defect in the gas valve as the problem. A bad electrical supply pretty much requires the repairman to have been negligent in checking that voltage. While that's always possible, everything reported so far suggests a competent and diligent diagnosis of the problem to me. Originally Posted by SeattlePioneer I would think that a repairman who is checking the burner manifold pressure and the gas valve voltage would be looking at that issue pretty carefully. And a Carrier three wire pilot that is turning the burner on and off repeatedly usually has the gas valve solenoid clicking on and off rather noisily. The absence of additional information from the repairman continues to lead me to suspect some defect in the gas valve as the problem. A bad electrical supply pretty much requires the repairman to have been negligent in checking that voltage. While that's always possible, everything reported so far suggests a competent and diligent diagnosis of the problem to me. Actually the older 5 wire gas valves were heat motor type and didn't have an audile click when opening and closing. They were Essex not White-Rodgers mfg's. I'm not trying to be argumentative. Wow, I am really grateful to find folks that care enough about this industry to share their wisdom. The unit is the Weathermaker SX (58SX080-JG-1). The pilot is the 3-wire pilot with a spark electrode. Oh, I did put a new spark electrode on as well (not the entire pilot assembly). FYI, most all of the parts that I have documented can be found on gsistore.com under Carrier/Bryant. This isn’t a plug but rather info on where I have purchased most of my parts. It is a good quick reference with photos. I believe the pressure readings were 11”wc. I watched the reading on his digital display as it would hold pressure and the briefly drop to zero and then immediately go back to normal. There isn’t any erratic clicking of the valve. I will order a new valve tomorrow if that still seems to be the culprit. It should be in sometime this week. I will keep you guys posted on the outcome. If you have any additional info, feel free to pass it along. Again, I am truly grateful for the help. You guys have a great week! Matt My recollection is that those early valves had the pilot and hold coils as heat motor coils, with the main burner operator a solenoid you could typically hear open. But perhaps my memory is failing on that point. Then you have the fact that most of those valves were changed out when one thing or another went bad. But speculation is only that without more facts. My bet continues to be on a bad gas valve, but perhaps I'll be proven wrong. I see that mbk3s speculation that there might be a three wire pilot has been proven correct. beachnut, is your existing gas valve more or less cubical, or sort of a flat rectangle, perhaps with a blue knob? Maybe you can provide the make and model of the gas valve. So far mbk3s guesses have been better than mine. But here's another objection to consider ---- if the main burner operator is a heat motor, why would you be seeing the rapid pulses in burner manifold pressure? Usually those operators are s-l-o-w to open and close. With a three wire pilot, standard procedure would be to clean the pilot burner and orifice. Those three wire pilots are famous for causing a variety of symptoms, and I'd clean it in hope that the problem beachnut has is another one of those. Go ahead--- prove me 100% wrong! The saga continues: The heat motor portion of the valve is the main valve operator. The pick hold portion is a single solenoid with 3 wires instead of 2. For what thats worth. S/P, you got me thinking about the lag time when a heat motor is de-enrgized (very astute observation). I don't know respond. Maybe I can think of some abstract lie. Oh yeah I remember....I invented the gas furnace and every control known to mankind. Did I spell astute correctly? The current gas valve is current part #EF32CW184A – modified for LP. It does have a blue knob. The following link will show you an image of the recommended replacement. It is pretty much identical in design -http://www.gsistore.com/cabrpaefgasv.html. Thanks for the additional information, beachnut. The valve you have does have solenoids which tend to have a click when they open that would be hard to miss. Still, any Carrier three wire pilot is capable of a range of tricks, and it's pretty much SOP to clean the pilot whenever something weird is going on. So my suggestion is to try disassembling the pilot burner and cleaning the pilot orifice. The hole of an LP orifice is quite tiny, and I'm not sure the best method to use to clean it --- blow it out from both sides might work. If it were me I'd replace it with a new one were it available --- it's a cheap part. Of course, now I'm expecting mbk3 to have a better idea.... Originally Posted by SeattlePioneer Thanks for the additional information, beachnut. The valve you have does have solenoids which tend to have a click when they open that would be hard to miss. Still, any Carrier three wire pilot is capable of a range of tricks, and it's pretty much SOP to clean the pilot whenever something weird is going on. So my suggestion is to try disassembling the pilot burner and cleaning the pilot orifice. The hole of an LP orifice is quite tiny, and I'm not sure the best method to use to clean it --- blow it out from both sides might work. If it were me I'd replace it with a new one were it available --- it's a cheap part. Of course, now I'm expecting mbk3 to have a better idea.... Wiseguy...lol I saw the pix of the valve and indeed it is the model you described with the audible click. Makes me think the valve has already replace once from the essex I believe was oem on that furnace..whatcha think Replacing the original cubical shaped valve is certainly the norm. Few survived very long, although I did replace one a year ago that was 16 or 17 years old. It was leaking gas because the valve was failing to close completely. So--- What odds do you want to give that cleaning the three wire pilot solves the problem? I don't really see how it could be causing the problem, but I'm guessing 2-1 odds that cleaning the pilot solves the problem whether it makes any sense or not! Originally Posted by SeattlePioneer Replacing the original cubical shaped valve is certainly the norm. Few survived very long, although I did replace one a year ago that was 16 or 17 years old. It was leaking gas because the valve was failing to close completely. So--- What odds do you want to give that cleaning the three wire pilot solves the problem? I don't really see how it could be causing the problem, but I'm guessing 2-1 odds that cleaning the pilot solves the problem whether it makes any sense or not! Whenever I taught the new (and older) guys at work I always said: The only absolute is....there is no absolute. Something always seems to be other then it should .. So, I have this exact problem, what did you replace to finally solve the problem? My suggestion --- Start a new thread and describe in detail what happens when turn up the thermostat.
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