Bosch Water Heaters - Recent Questions, Troubleshooting & Support

check to see if voltage correct if not replace board if ok bad ignitor

possible missing or bad gasket or o ring

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.

If you can't hear clicks, then very likely it is the "microswitch" that is a rectangular white plastic box that can be seen at the bottom of the unit from underneath. It's purpose is this: when there is gas pressure, a pushrod turns the switch on, thereby allowing electrical current to flow from the "hydrogenerator" to the igniter unit. The hydrogenerator generators from about 1 to 2.5 volts AC (not DC) when water is flowing, powering the generator which powers the igniter unit....assuming the microswitch is allowing electrical current (the voltage) to pass through. It is a "self-adjusting" switch because the pushrod can come out at different pressures. So if your gas fluctuates, the microswitch will be fixed to a higher pressure level, but not be able to turn on if the pressure drops. This is because the pushrod is not pushing as far. It's simple to unscrew the plastic box and push the teethed switch setting back to the initial default position, and then carefully replace the plastic cover. Then do it again next time it stops working, a year or two it seems for many people. You can take out the switch and connect it's two wires directly, but if there is no gas pressure and you let water flow through, the igniter unit will constantly be sparking and thereby might fail early. If there is no gas pressure, then maybe it is because of a local leak and thereby bypassing the switch is a built-in explosion hazard, but that would require the sparking to no longer be internal to the ignition unit.

WOW!!!
Great answer by Steve (I know Steve Spam...real name Richard). Lot of time on his hands (37000 answers).

Can we get real professionals answering questions.

Thank you Richard...let's just call you Dick for short.

You are looking for a mechanical problem for an electrical issue. This unit is controlled by an electronic board. That board is the cause of your issue. They are about 300 dollars.

Are you holding the flame button until the thermocouple heats up.

you dont drain theses type water heaters

you can not drain these w/ heaters

first id check shower head most has a screen in them and do get clogged from time to time since the water flows good from faucets

One possibility - insufficient gas flow or oxygen starvation might be making the pilot light dip when the main flame is on so the thermocouple bulb is no longer heated. This will cause the main flame to go out and restore full pressure/sufficient oxygen to the pilot.

Is Bosch 1600is the correct model #, or 1600ps?

Slim chance but this link might have it https://www.manualslib.com/