[Dan Powers]

I have an old Thermador GSC30 (1991) drop in range/oven that recently blew the main control block. The service tech replaced the control block, and we also soldered loose pins on the front control panel potentiometer to get it going again. Everything works well now except for one minor problem. The cooling fan, which engages when the oven is turned on, continues indefinitely. It does not cycle off after a reasonable cool-down period like it should. To turn it off, I trip the main breaker and all is well. I was planning to open this up again (requires a special burner tool so I need to get that). Any advice on what to look for or what the problem might be, or how to fix it (other than install a reset switch somewhere in the power supply.)

Thanks,
Dan

[Servicer]

Hello,
The way the GSC works, is it will keep the fan running until the oven sensor reads that the inside of the oven is below 350. At this point the clock cuts the DC voltage leaving out to the relay board that keeps that fan energized.

The fact that, simply, resetting the breaker causes the fan to shut off tells me that the clock is what's keeping that fan running. To my knowledge, if it were a stuck relay it wouldn't unstick itself when the power is removed. Also, if the range seems to be cooking at the correct temps, the sensor should be OK.

The only other thing I can think of is the possibility of the heat that's raising up into the control panel is causing the harness on the clock, which is where the sensor plugs into the board, to expand and lose connection. When this happens the total resistance on the sensor circuit can increase which can trick the board into thinking the oven is still above 350°f. This isn't likely, but possible. A good sensor reading is 1100 ohms at room temp and ~1650 ohms at 350°.

Good Luck..

[Servicer]

Hello,
The way the GSC works, is it will keep the fan running until the oven sensor reads that the inside of the oven is below 350. At this point the clock cuts the DC voltage leaving out to the relay board that keeps that fan energized.

The fact that, simply, resetting the breaker causes the fan to shut off tells me that the clock is what's keeping that fan running. To my knowledge, if it were a stuck relay it wouldn't unstick itself when the power is removed. Also, if the range seems to be cooking at the correct temps, the sensor should be OK.

The only other thing I can think of is the possibility of the heat that's raising up into the control panel is causing the harness on the clock, which is where the sensor plugs into the board, to expand and lose connection. When this happens the total resistance on the sensor circuit can increase which can trick the board into thinking the oven is still above 350°f. This isn't likely, but possible. A good sensor reading is 1100 ohms at room temp and ~1650 ohms at 350°.

Good Luck..

[Dan Powers]

The problem appears to be in the front panel (clock). The new control block is OK. In fact I now have a spare block for this unit if anyone wants it. The clock is trickier, since there are no replacement boards, it must be sent back to Thermador for rebuilding. I resoldered a couple of pins on the clock potentiometer so I might revisit that.

[Servicer]

Actually, it will need to be sent to CG Industries. Thermador doesn't rebuild their old parts.

CG Industries - America's top remanufacturer for residential appliance parts.
866-737-2244

[kayakcrzy]

Replace the sensor, before you send your clock back. Tom ApplianceEducator.com