Landscape lighting shows no voltage sometimes

Question

I have a Malibu transformer that puts out 12V 88W MAX. It powers four lights at 12V 18W (incandescent) apiece. I think there is a run where one cable powers two lights. I dug up the cable on the second light run and found what I would call a "vampire connector" that kind of bites the wires to make a connection. I assume there is the same thing on the first run, although I cut the cable from the lamp to allow me to remove a stake which was causing the light to lean.

The end of the cable (in the run) has 12V when I turn on the switch.

At the first light on the cable I get an inconsistent reading, it seems sometimes I get 12V, sometimes nothing and when I twist it together to connect the lamp I get nothing at that connection. This is the problem, I am getting power but when I connect the lamp I get no light.

I don't know what else to try.

-update: I added a new "quick clip connector" to A and the light now works there.

diagram:

Answer 1

Given that you measure voltage but when the light is plugged in it doesn't light (and assuming the bulb itself is not broken) you're almost certainly looking at a poor connection - or possibly more than one of them.

Using a spare socket or even just some stripped wire, ensure that the bulb lights when wired to the transformer outputs right at the transformer.

Next, test the bulb at the far end of the cable.

Finally, measure voltage at the far end of the cable while the bulb is plugged to the socket it belongs in. From the preceding tests you'll know the bulb itself is good and the connection of wire to transformer is good. If the bulb doesn't light and the voltage at the far end of the cable stays near 12 v, you can be fairly confident the problem is in the "vampire connector" splice or in the lamp socket. Replace the splice, test, and replace the socket too if it still doesn't work.

Or - go with probability and replace the vampire connector as step 1. An underground connector with minimal, if any, protection against water ingress is bound to fail sooner or later.