If there is not a clicking sound, it almost always means the main ignition or control unit (box with red and green lights and wires coming from it) is not getting the supply voltage. The voltage is supplied by a generator that is getting energy from the flow of water (the "hydro generator"). First disconnect the wire connector at the hydogenerator and check the voltage while water is running. The manual says you should read 1.6 VAC (I read 2.5 VAC). Make sure your voltage reader is on AC, not DC. If you have at least something like 1 VAC, then the next thing to check is the "microswitch" that allows the hydro generator voltage to reach the ignition unit. To check it, disconnect the other wire connector that is on the black wire coming from the hydrogenerator that is closer to the ignition unit. Then with the water running, stick a small screwdriver in the male plug side to short the two wires in order to bypass the microswitch (per Bosch tech support instructions). You should now here clicking and see the unit work. This is what happened with me and tech support said I needed to order a new microswitch and gave me a part number and telephone. But don't stop reading here. You can see the microswitch when looking up at the underneath of the unit. It's a small white 1x1 inch box-like shape held by 1 screw. After removing it, I noticed the microswitch had a removable cover (which is strange for a switch) and opened it to discover the internal switch can actually move inside because it "automatically adjusts" itself when it is first put in (it stays more firmly, but not rigidly in place when the cover is on). So you can mess up when putting it in. Don't bump it. It can easily get out of its working range of motion, which is why mine stopped working: it was a bad design to use this type switch in this application. So I slide the internal switch back close to the spring side ("default" position), put the cover back on, carefulyl screwed it in place, and now it works.
The purpose of the mechanical microswitch is to not allow the hydroenerator voltage to the ignition unit unless the "pushrod" has opened the main gas supply. It prevents clicking if there is no supply gas, so it is not needed (you can electrically bypass it with a splice) if everything else is working fine. But don't blame me if you do this and for some reason it ruins the more expensive ignition unit. The microswitch is turned on by the pushrod when the pushrod leaves it's default position. The the pushrod moves only about 2 to 3 mm when you turn on the water. You can see the pushrod when you unscrew the microswitch, and you can watch it move. The problem is that the microswitch mounting is not precise enough for the small pushrod movement and the pushrod's default position can change with age of the diaphragm or change in the grease. So their automatically adjusting microswitch that makes up for lack of precision in design and pushrod movement can stop working when the pushrod changes position. My unit was 2 years old.
what a pain the microswitch is. mine needs "adjusting" just about every other day, after 2 years of minimal use in my garage. after reading this, i put in a switched splice, meaning i can have the circuit complete any time with the switch. i don't think this will affect the ignition as it only completes when water is running, in other words when it needs to be fired up. bad design but otherwise the heater works great.
Fixed my issue as well. Looked all over to try to fix this problem, even boschs website. Do they even mention this? No, go figure. Thanks tons
geno! You Rock!!! Thanks so much!
Worked for me also, thank you.
I bypassed the microswitch because it wouldn't adjust for me. There are already enough safety features, and the gas valve won't open nor will the ignitor throw a spark w/o hydrogenerator voltage output from water flow. Nary a problem in 8 years.
Zawy! you are correct! thanks for the post!
I got no spark/light/unit function when shorting the male end connecting to the microswitch. Why? I manually thrww the microswitch and still nothing happened. Water getting on the wires during drainage could ruin them and need to be replaced, correct? What about checking the control box/on-off box?
×
This was a life saver. Bosch tech help was RUDE! Can't believe this was the fix. They refused to converse with me because Im not a tech. Thank you thank you
2,683 views
Usually answered in minutes!
×