12V transformer issue

richs555 · 08-02-2009, 02:16 PM

This 120V/12V transformer has 2 black wires on one side of the seperator, 2 white on the other side and a ground nut on the seperator. the 12V light has 1 black and 1 white. of course i have a black, white and ground from the 120V line. how do i wire this up? it is obvious i don't match the blacks to blacks and whites to whites. do i connect the whites on one side of the transformer to the 120V in or do i connect the blacks on the other side to the 120V in? dazed and confused.

Gigs · 08-02-2009, 05:10 PM

That's pretty confusing. You might need to take a picture. You need to find out which side is the primary and which one is the secondary. The colors might not mean anything... there's not always standard colors on transformers.

kbsparky · 08-02-2009, 05:57 PM

What is this transformer for?
Got a make and model number?
What is the rating in watts, or kVA?
Are the black wires larger than the white ones, or smaller?

richs555 · 08-02-2009, 07:40 PM

so on the transformer it has a decal that has the primary (120v) on the right which is where the 2 blacks are and the secondary (13.9v) on the left which is where the 2 whites are. coming off one of the whites is a fuse-like transducer/reducer i am guessing which must reduce the voltage by 2 volts and must connect to the black leading to the pool light. the other white to white. the problem is that i can't figure:

1. which of the two blacks on the primary side goes to the black hot feed? or does it even matter?
2. when i put a meter on the 2 whites on the secondary side i should get a reading of 12-14 volts but i get nothing.
3. why do i get a continuity reading off the 2 whites on the secondary side but not on the 2 blacks on the primary side?

this confuses me. attached is a picture although not very good.

Thurman · 08-02-2009, 07:54 PM

I think I see what you are trying to describe: The two "black" wires appear to be two conductor lamp cord, thereby the insulation on both wires are black. The other cord just happens to have two conductors also and the insulation is white on both wires. Usually on a 110 volt supply like this it really doesn't matter which wire is the "hot" wire, but it may matter in this case, if your transformer calls for a "hot feed" connection. Look at the two black insulated wires closely, is one of them somewhat smooth, and the other has maybe "ribs" running along the length of the wire? If so, I believe the one with the ribs will be the neutral wire and the smooth wire the "HOT" wire, (someone back me on this). You will just have to know which prong on the male plug it "HOT" and which is neutral and wire it correctly. Good Luck, David

Gigs · 08-02-2009, 08:19 PM

It sounds like an open primary if the two black wires show no continuity.

Probably a blown internal fuse. Throw that antique away and get a new one.

kbsparky · 08-02-2009, 08:57 PM

You have a bad transformer, with no continuity on the primary windings.

Time to get a new one, and they ain't cheap.

micromind · 08-02-2009, 09:28 PM

What do you mean by 'no continuity'? If you're using a standard digital multimeter and the 200 ohm scale, the test might be invalid.

The resistance across the primary of this transformer could easily be more than 200 ohms. Try using the 2000 (2K) scale. If it still shows no continuity at 2000 ohms, then there's something wrong.

Usually, when a transformer like this burns up, the primary winding will open, not the secondary.

Often, the problem is the connection of the lead wires to the actual winding. The winding wire is solid, and easy to break.

Rob