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I have a gas Thermador Range/Oven (PRG304) that has an oven problem. The oven will originally heat up to temperature and turn off as it should. But after the initial heat up, it will not fire again. The broiler seems to work fine.
My thought was that the dual gas valve was the problem and I have replaced it. But I still have the same problem.
How do I determine what the problem is? The only two parts I can think to replace at this point are the thermostat and the control unit. Both are expensive parts so I hate to replace the parts unless I can determine if they are the problem.
BTW, I have replaced the Spark Module (because the burners were not getting a spark).
Please help!
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Rank: Member
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I found a post by Servicer about a similar problem that said:
"...you need to check for 3.2 amps from the glowbar. If you have 3.2, but not gas it's the dual valve. If the amperage is less than 3.2 and you have around 120vac it's the igniter."
Does anyone know if it is possible that the glowbar would have 3.2 amps at the initial burn and then perhaps not have enough amps for the second burn? In other words, is it possible that my glowbar is starting to fail and that is why I'm having troubles?
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Rank: Advanced Member
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Hello,
I've never seen where the glowbar would draw the proper amount then stop; usually, the glowbars are either good or bad. Given your symptoms, I would focus more on the thermostat or a possible bad relay. Using the attached diagrams, you can see that the power leaves out of the T-stat, goes through the relay (this is the relay mounted behind the console), through the valve then onto the glowbar.
What this occurs, check for power leaving of terminal number 2 of the t-stat. If it's there, check for power coming into the common (COM) and leaving out of the normally closed (NC) terminal of the relay. If yes, the next point it hits is the dual valve. Being that it's new and your symptoms are the same, it's safe to assume that the valve is still good.
The only way to check the glowbar is from behind the unit when the problem is occurring. You'll have to be behind the range because the unit will be too hot to check from the inside. From the back, you should be able to get to the wires going to the glowbar. If you have 120v, but are not drawing proper amperage, it will be a bad glowbar.
Good Luck,
KC
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Rank: Member
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Thank you very much for your reply. I have a few questions: Originally Posted by: Servicer  Given your symptoms, I would focus more on the thermostat or a possible bad relay. Using the attached diagrams, you can see that the power leaves out of the T-stat, goes through the relay (this is the relay mounted behind the console), through the valve then onto the glowbar. I see the relay on the wiring diagram, but where is it on the unit. I see the convection fan relay on the burner box, but I don't see any other relay. Is it the same relay? Originally Posted by: Servicer The only way to check the glowbar is from behind the unit when the problem is occurring. You'll have to be behind the range because the unit will be too hot to check from the inside. From the back, you should be able to get to the wires going to the glowbar. If you have 120v, but are not drawing proper amperage, it will be a bad glowbar. Isn't the glowbar for the oven accessable from inside the kick panel on the front? Unless I do not understand I think it is the broiler glowbar that is only accessable from behind the unit. My problem is with the oven rather than the broiler. Am I confused? BTW, I didn't see your attachments. I'm using the wiring diagram from this site, but it is not high enough resolution to see the terminal numbers and such. Do you have a better diagram that I can use? Thanks! Jim
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Rank: Advanced Member
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Hello, For some reason, Thermador calls that a convection relay, but it's only purpose is to switch power between the bake and broil circuits. Regarding the glowbar, I thought it was wired from behind. Sorry, I'm getting my models confused. I've attached the PDF file again. If it doesn't work, there may be a problem with the site. KC EDIT - If the heat light is on while this is occurring, the thermostat it not the problem.
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Thank you, thank you, thank you!
Yes, the heat light is on while this is occurring.
One more question:
If the glowbar is lighting up, but there is no gas to burn, doesn't that point to the glowbar in a way. Because the fact that the glowbar glows means that power is coming from the T-Stat, through the relay to the glowbar. I was thinking that perhaps the current is flowing but that there isn't enough flow (lower than necessary AMPs) to open the valve. Is this possible?
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Rank: Advanced Member
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No problem.
Normally, if your current is low, e.g. 2.8 amps, the valve/flame will sputter. Also, it's not likely that the glowbar would be intermittent. If it was an intermittent glowbar, odds are there would be times the unit would not start its initial preheat.
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Well I think I just blew the gas valve. Here is what I did:
I turned the oven on and then checked the voltage coming from the relay and going to the valve/glowbar. I was getting 118 volts according to my meter. So I figured the relay was fine and moved on to check the amperage on the neutral side of the glowbar which my meter showed at 1.19 Amps. But then I wondered if I was supposed to check the Amps before the glowbar, so I checked there. When I did this I blew the breaker. After resetting the breaker I found that the glowbar did not glow anymore. So I checked the voltage at the relay again and I still have 118 volts. But I checked the voltage in front of the glowbar and I have nothing. As I understand it, the only thing between the relay and the glowbar is the gas valve. So I'm thinking I killed the valve. Now that I made an expensive mistake let me ask the following questions:
1) What is the proper way to check the amperage for the glowbar?
2) Is the fact that I was only seeing 1.19 Amps after the glowbar point to a bad glowbar?
One other item to note, I checked the resistance for the glowbar and my meter showed 125 Ohms. Is there some spec that I should be looking for?
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Rank: Advanced Member
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Quote: Well I think I just blew the gas valve. Unfortunately, it sounds like it. Quote:1) What is the proper way to check the amperage for the glowbar? The best way is to use a clamp-on meter on either the hot or neutral side. You can use one line or the other, but not both at the same time. Quote:
2) Is the fact that I was only seeing 1.19 Amps after the glowbar point to a bad glowbar?
One other item to note, I checked the resistance for the glowbar and my meter showed 125 Ohms. Is there some spec that I should be looking for?
These are both signs of a bad glowbar. Using Ohm's Law (Voltage = Current x Resistance), the resistance should be 37.5 ohms. On a side note, using the numbers you've given, your voltage should be 148vac, so I think there may be something wrong with your meter. 1.19 amps x 125 ohms = 148 volts.
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I ordered the new parts. I'll update my results as soon as I get the parts and install them.
BTW, is there any problem testing the resistance of the new glowbar with my meter before I install it? Can I damage it in any way? I'm just curious to see what my meter will show...
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