GAS VALVE ON HEATER DOES NOT OPEN


As I am getting a little older, I'm getting lazy. Called Heating Repair to assess no heat from a BDP furnace. When told gas valve was defective, wife implored let him fix it. This was after $89 diagnosis fee not applied to $450 for valve. EF 32CW 183 replaced unit not working; now told igniter defective, then printed circuit board defective. As I am an elec engineer, I informed tech that multiple problems were not likely. Checked old solenoid coils have appropriate impedance.
After throwing tech out, got off my ass and inspected furnace. Solenoid is clicking but no ignition. Checked wiring and by placing a little pressure on connector to printed circuit board furnace ignited and functioned normally for about ten days.
Then stopped working. Inspected again and cleaned connections with switch cleaner. Now, pilot ignites, small fan does not turn (I think this flue fan did before) and after 5 seconds or so instead of gas valve fully opening goes back to clicking solenoid. I think either the flue is not present due to the fan not turning or less likely, the bimetal is not reacting to the pilot flame.
I am an experienced hands on engineer who can fix anything, given adequate schematics. I understand safety. Can anyone explain the appropriate start sequence with voltages at appropriate locations? I have a pretty good general idea, and have worked on old furnaces before (my own). Thanks in advance for any help.
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ADDITIONAL INFO:
WHEN FLUE SWITCH IS SHORTED BURNER LIGHTS. Now to determine why inducer motor not working, I think.
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until the radio worked. And he was as close to "anyone" as you can get.
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THANKS FOR THE REPLY. THE MOTOR IMPEDANCE IS NORMAL. SO NOW NEED TO CHECK THE RELAY (SOLENOID) VOLTAGE AND DETERMINE IF IT IS SWITCHING.
QUESTION: 1. DOES THE INDUCER RUN CONSTANTLY THE ENTIRE TIME THE FURNACE IS ON? I THINK YES.
2. THE VOLTAGE LOOKS LIKE 110 ON THE SCHEMATIC. I AM THINKING OF SUPPLYING 110 TO THE FAN DIRECTLY WITH JUMPERS BYPASSING THE RELAY TO TEST THE MOTOR WITH VOLTAGE. IF IT WORKS THE THE RELAY IS BAD.
3. SINCE THE RELAY IS SEALED ON A PRINTED CIRCUIT BOARD, CAN IT BE REPLACED WITHOUT REPLACING THE BOARD? ANY 110 V RELAY SHOULD WORK???
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This all worries me too. I get a lot more upset when someone I hire messes up than when I mess up myself. And I'm getting lazy too.

I have no idea if it is 110 or not, but if there is no transformer to lower the 110, probably is. If there is a transformer, you can probably find two points near the relay to measure if it 110. If you can't merely replacing the relay likely won't work.

Not counting the obvious, single pole/double pole/etc, not big enough, yes.
Again, I haven't seen what heater boards are like in the last 20 years, if they are still single layer or multiple layer. Mulitple layer could be very hard, but on single layer, if your relay won't fit in the space, you can run wires from all the pin mounting points and put the actual relay anywhere you want.
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scidoc wrote:

    In order to exhaust the flu fumes, the fan will run prior to the lighting of the burners and continue until the flame goes out. YES.

    Looking at the motor faceplate for the inducer should tell you the voltage it operates on. Mine use 110 volt AC and I would GUESS yours is probably the same. It sounds like you are on the right track and understand where to look. Of course the relay is (probably) driven by a DC voltage so the problem could be further back. Establish the operating voltage of the motor, and measure what is applied when heat is called for by the thermostat. If it is 110v and it is being applied, then the motor or a motor start cap is your problem.

    You sound like you know more than the guy you hired, but do NOT jump to conclusions in trouble shooting a circuit. Establish what is incorrect and back up until you find what is not functioning as it should. If the relay is failing to latch and all voltages are there, only then should you seek a relay.
To answer your question regarding the relay: Anything can be repaired if you can acquire the correct tools and parts. Most manufacturers do not "Re-invent the wheel," and use readily available parts. Some however do in order to force your purchase of their products.
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OK; BEERS FOR ALL!
TAPPED THE RELAY AND A SMALL SPARK WAS VISIBLE AND THE FAN MOVED FOR 200 MSEC. REMOVED THE PRINTED CIRCUIT BOARD AND LO AND BEHOLD; A COLD SOLDER JOINT UNDER THE 110 SIDE OF THE RELAY. SOLDERED PIN, REINSTALLED BOARD. ALL IS WORKING. THERE IS STILL HOPE FOR US SELF REPAIR GUYS IN THIS WORLD.
THE MOTOR IS 110. THAT PROBABLY CONTRIBUTED TO WHY THE SOLDER JOINT CRACKED.
THANKS FOR ALL THE HELP AND SUPPORT.
LET THERE BE HEAT!
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NOW THE HEATING GUY WANTS TO CHARGE $500 FOR REPLACING THE GAS VALVE AND NOT FIXING THE FURNACE. 2 DIFFERENT TECHS CAME OUT. WAS TOO ANGRY TO TALK TO THE OWNER WHEN HE CALLED LAST WEEK. NOW I HAVE CALMED DOWN A BIT.
ANY IDEAS ON HOW TO DEAL WITH THIS GUY WOULD BE APPRECIATED? THE NEW GAS VALVE IS IN, THE OLD GAS VALVE HAS A GOOD SOLENOID.
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scidoc wrote:

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    If it were me, I would offer him something like half of what he wants. Tell him if he does not take it, remove and replace the old units and you will report the incident to the BBB and whatever organization that licenses his company. There are surely good people out there, but too many are crooks counting on the customer to be dazzled by their BS. Good luck.
    If you would like to see more examples, go to the news group alt.hvac
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I've watched this story with interest. I've had similar problems with many of the "pros" around here. Just because they are licensed doesn't mean they are competent!
Doug
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Doug wrote:

    That Doug, is the understatement of the year!!! I have been in my present home for over 30 years. It was new when I bought it, and less than two years after I moved in one of the condenser units stopped running. Since there were stickers applied to the furnace and AC stating who had installed them and it was so new, I figured I would call them to fix what I thought was still under warranty.
    A "Tech" came to my house and inside of ten minutes diagnosed my problem as a faulty compressor. Thinking that this would surely still be covered, I said something like "Go ahead, it won't cost me anything." To which he informed me that the compressor was covered but the labor was NOT. That labor would be $600.
    Having a background in electronics and also being nosy, I watched him "Diagnose" the problem. He never once took out a meter to see if the contactor was being activated by the thermostat, nor if it even had power going to any of the components. I watched in disbelief not saying a word because I wanted to see whether they were honest or not. I saw all I needed to see and told the "Tech" I would contact him when I decided what I wanted to do. After he left I took out my meter and inside of five minutes determined there was no 24v AC at the coil for the contactor. Looking at the wires going to it I saw they were spliced (perhaps I should say wrapped) and covered with electrical tape. Opening the tape showed oxidation and a poor connection. Once soldered and taped the unit ran fine. I might also say it ran fine for another 30+ years!!!!!!!!
    Now I am not a HVAC person, nor have I been trained in the trade. There is much I cannot and will not attempt. There are however many simple tasks that a person with very little skill can attempt without jeopardizing the safety of their family. When in doubt, DON'T. It is a shame that so many of those in the trade are either incompetent or dishonest. I would be very upset if their acts tainted my trade and I were one of the honest ones.
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