Friday, May 25, 2018

Bosch HGS235UC/01: even after replacing igniter and gas valve, still no heat in oven

I have had a problem with our Bosch HGS235UC/01 gas range for some time. When I set it to the oven convection bake or regular bake mode, it would not heat up in normal time. The igniter became red-hot but the gas would not ignite until 20 minutes later; this delay became longer over time.

The igniter was the main suspect, so I decided to replace it on my own. But, to verify that this part needed to be changed, I tried to measure the current flowing through the igniter, which should be between 3.2 A and 3.6 A (as I understand it). Unfortunately, one of the meter probes with the igniter wires made contact with the metal panels underneath and caused a short-circuit and sparks to fly. This permanently damaged the coil inside the gas safety valve. I ordered a new igniter and new dual gas valve assembly. With great difficulty and effort (German engineering with no access to the screws, requiring dismantling of the whole unit!!!), I replaced these two parts.

Now, the igniter seems to work fine with about 3.4 A measured through it. Alas, for some unknown reason, the gas valve doesn’t open and as a result, the igniter doesn’t ignite the gas, because it’s not flowing. I’m really baffled because the gas valve coil and the igniter are connected in series, so the 3.4 A current has to flow through the gas valve coil as well, which should open the gas to the oven, but it doesn’t.

One thing that I noticed is that there’s a blinking red LED light (LED1) on the power board. What does it mean, and is it normal? Maybe, I damaged something on that board.
Of course, I should mention that the top of the gas range works fine, so there is no problem with the main gas supply. I could check the power board, but I don’t have access to the schematic, nor the service manual. If anyone has it, I would greatly appreciate a copy.

Also, any ideas are welcome. At this point, I’m quite desperate because it’s the third day that I’ve been trying to fix it, and my wife has become quite upset, as you can imagine.

via Bosch HGS235UC/01: even after replacing igniter and gas valve, still no heat in oven
by Krakus

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