Question : How to replace a D-cell with a universal adapter instead

I have two propane "on demand" water heaters that heat our swimming pool. Since they run pretty much 10 hours a day, the little D-cell in there doesn't last much longer than 3 weeks or so. I think the D-cell helps in igniting the flame, but I'm not sure what else it does. If you take it out the flame dies.

So my idea so I don't constantly have to be changing batteries is the following:  I've got this universal AC-DC adapter (see pictures).

 

DSC09929.JPG (1.9 MB) (File Type Details) 

Adapter 1

 

DSC09936.JPG (2.1 MB) (File Type Details) 

Adapter 2

There is a variety of ends on the unit, but none, of course, mimic a D-Cell.  So this is what I was thinking of doing:
1: Set the adapter to 1.5V
2: Strip the wires of the adapter and soldering one to the positive side and one to the negative side of where the D-Cell would normally rest in the water heater.
3: Plug it in and hope it works. If it doesn't work, I'll switch the polarity and try again.

So anyway, I have no knowledge of electronics and I'm not sure what I doing wouldn't wreck something, so I wanted to check with Experts Exchange first.

Lemme know. Thanks.

Answer : How to replace a D-cell with a universal adapter instead

Put in on DC Volts, make sure the red (postive) and black (negative) are plugged in correct on the volt meter. attach the leads to the wires if the voltage read is postive, the red lead is connected to the postive wire and black connected to the negative otherwise the voltage will be negative, switch leads, the voltage will be postive and the red lead will be on the postive wire.

Please note on some of these adapters the polarity can be set with a switch on the adapter. Not sure about yours. Basically if you slide the switch the polarity changes.

The white line should be so you can tell the wires apart.

Also make sure to solder so the connections do not ever spark.