Voltage at the tap too high, 150 w transformer

Ole Olson

New User
150 watt transformer w 3 fixtures, each w 20 w halogen lamps. First fixture (at the middle of the run, where we T) is 15 feet from transformer. The other 2 fixtures are 15 feet from the T. So this is a very close system.

We are getting a 13.6 v reading at the 12 tap, causing the lamps to burn bluish green. We coiled 30 ft of 12/2g wire, and placed that between the tap and the primary wire, with no reduction in volts. So we tried, first, a coil of 14/2g, then 16/2 g. Still no reduction in voltage.

We double-checked the accuracy of the True meter with a new meter. There is 124v coming out of the receptacle, which is within normal range.

What else can we do? Is a 150 w transformer less precise at reducing voltage than a 300 w?


Staff member
Landscape lighting often uses a transformer voltage higher than 12.00, and automotive 12V bulbs are really specified for 13.6 volts or higher, since the battery may be on charge.
A Malibu (TM) system will specify a minimum length of a maximum wire gauge between the transformer and the closest incandescent lamp to avoid just the kind of problem you are seeing.
When dealing with "12 volt" it is a good idea to confirm that all of the components are on the same page with respect to actual design voltage.

A back to back parallel pair of power or zener diodes in series with one lead may solve your problem.

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