Question about Intermatic Malibu 300W Power Pack Transformer ML300RTW

1 Answer

Malibu landscape lighting transformer problem

I have a Malibu MT600TW transformer which is not working. When it is plugged in and turned on, and I place a voltmeter across either of the A-B terminals, I get no voltage reading. An ohmmeter measurement seems to show that the A-B terminals are connected, which I assume is a problem. Could this have been caused by the terminals getting wet or something?

Posted by boolam on

  • 5 more comments 
  • boolam May 30, 2009

    Thanks for your help.

    No, there are two A-B terminals and each one is for a different 300W circuit. The two wires for each circuit are connected to A and B (one to each). The manual with instructions can be found at

    When I check the voltage, I just place the two voltmeter leads on A and B (one on each), then I switched to the other direction just to make sure the polarity is correct.

    I assume there should be 24V across these two terminals? Yes, the timer/switch is working, and the transformer is getting 120V, I checked both of these.

    Thanks again.

  • boolam May 30, 2009

    You were right on all counts ... I was checking DC volts, and it is a 12V system not 24V. And I understand your comment about continuity through the transformer windings.

    So I gotta look for another reason why the lights aren't working.

    But thanks for taking the time to reply! You were extremely helpful.

  • Samuel Charles Spriggs May 11, 2010

    I'm going too fast here. Of course, you have 12 VAC on the A/B terminals or you wouldn't be looking for another reason for no lights.

    If you only have one circuit in use, maybe there is a cut wire. I would first check the continuity through the line going to the lights.

  • Samuel Charles Spriggs May 11, 2010

    Thanks for the reply. I'm not ready to quit yet. Did you check the output on the A/B terminals and it is zero?

  • Samuel Charles Spriggs May 11, 2010

    Sorry, one more point. There should be continuity across A & B terminals. The meter is measuring the resistance of the secondary coil in the transformer -- if you got no continuity across these termianls that would be a problem -- the coil would have an open circuit which would render it non-functional.

  • Samuel Charles Spriggs May 11, 2010

    Please don't take offense, but did you have the voltmeter set to A/C volts?

    I didn't see any electrical specs in the pdf above, but every outdoor lighting transformer I've ever seen has a nominal output of 12 volts A/C.

    When you mentioned polarity, that kinda told me you were checking for DC voltage.

    But, be that as it may, I assume it won't light up anything, and that is the symptom of concern -- is that correct?

  • Samuel Charles Spriggs May 11, 2010

    I could only find the ML600TW on line.

    But in any event could I get some clarification?

    Are the A & B terminals for different circuits?

    When you check for A and then B voltage, do you use a common terminal to do this?

    Have you confirmed that the timer/switch are working and the transformer is getting 120 volts?




1 Answer


Testing ohms across A and B will read open circuit through transformer coil.
Testing DC voltage across terminals A and B should read 12 volts DC, and nothing less.
Transformer should make humming sound when working.
Test that receptacle has power and breaker is not tripped.

There are no repair parts for power packs, but they come with 5 year limited warranty.

For more information on Intermatic/Malibu power packs showing troubleshoot steps, replacement trippers, useful links, warranties and tips:

Posted on Mar 05, 2011


Add Your Answer


Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

We have a Malibu 300 low wattage transformer for 13- 20 watt landscape lights.

Try connecting a lamp (correct voltage, etc) directly to the transformer. Most likely, the wire from the transformer to your lights is broken... The reset button can't reset anything, if there's nothing wrong there.

Jun 16, 2016 | Intermatic Malibu 300W Power Pack...

1 Answer

Where can I buy a replacement photocell for my Malibu 300W low voltage landscape lighting transformer?

You can buy the Malibu Photocell Low Voltage sensor on eBay. Go to eBay and search "Malibu Photocell Sensor" and you should see it. Or search eBay item number 371829265599

Mar 26, 2016 | Intermatic Malibu 300W Power Pack...

2 Answers

Problem with Malibu Landscape Lights Transformer ML900TW

Use an extension cord to plug the transformer into a different "test" GFCI receptacle, if it holds on the test GFCI you know that the GFCI for the transformer needs replaced. If it doesn't hold, then the transformer is on the way out and should be replaced. Sometimes motors and transformers will "leak" current and still work, but not trip a regular circuit breaker. A GFCI that is doing it's job will catch it though. Don't force a GFCI like can wear it out prematurely.

Apr 24, 2012 | Home

1 Answer

Using Lowes mechanical timer in Hadco TC654-15 landscape lighting transformer. Have tried 3 timers now and timer clock does not work when plugged into the transformer. if I bypass the timer, low voltage...

Always a good idea to check outlet with cheap circuit analyzer.
And move timer to different outlet to see if difficulties are outlet-specific.
Try timer at neighbor's house.
Having 3 defects in a row is unusual.

There are no repairs for defective timers.

Timer clock motors stop working for many reasons, bad manufacturing of plastic gears and power surge and dirt and reversed polarity among the causes.
Using household plug-in timer is typical solution since clock modules are not sold separately.

Following link gives tips for having low-voltage power pack last longer, in case you decide to buy Intermatic-Malibu from Home Depot:

Aug 31, 2011 | Hadco TC151-12TP Accessory Transformer

1 Answer

We have an outside landscape light time that has quit working. Model pb115m1. Do you carry these?

Fixya does not sell timers or parts.

Timer system is not identified for certain.
If landscape system still turns on-off with override switch, then you can work around and buy cheap plug-in timer, set landscape to override, and plug landscape system into cheap timer.

Open following link for low voltage transformer resources:

Add a comment for more help.

Take a moment and rate answer:
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on timer or any do-it-yourself project.
Fixya is always less expensive than a service call.

Aug 28, 2011 | Hardware & Accessories

1 Answer

Lights will turn on and off manually only

Just checking, still plugged in, fuse or circuit breaker not tripped that provides power to it? If you can turn it manually, and the dial does not turn when powered up, look for a small on/off switch, other than that, maybe it does need replacement, but they usually last longer that a year, but I have had some timers that just quit working on me too.

Apr 29, 2010 | Intermatic Malibu 300W Power Pack...

1 Answer

When i plugg in my power pack it instantly tripps the breaker in my power box. i un plugged it and disconnected the wires it worked fine since june when i bought it. iturned it off over dec. because of...

Guess is that the primary winding on the transformer (in the box) has a shorted winding. No fix. Replace the transformer.... and be sure that the load (total wattage of the lights being serviced) does on exceed 90 percent of the power pack capacity.

Jan 09, 2010 | Malibu ML200RT - Low Voltage Power Pack...

1 Answer

Malibu landscape transformer

I discovered that I hadn't turned the manual switch to off on the one that wasn't working properly.
Now they both work fine. The instructions that come with the Malibu Transformer is not easy to understand and it does not go into enough detail. There isn't a trouble shooting section which would help.

Apr 14, 2009 | Intermatic Malibu 300W Power Pack...

1 Answer

Malibu landscape transformer

If it is keeping time try moving the stops. If it is not keeping time the motor is probably burned out. These transformers don't have a lot of serviceable parts to them.

Oct 29, 2008 | Malibu ML600TW - Low Voltage Power Pack -...

Not finding what you are looking for?
Intermatic Malibu 300W Power Pack Transformer ML300RTW Logo

7,658 people viewed this question

Ask a Question

Usually answered in minutes!

Top Intermatic Hardware & Accessories Experts

Gene Haynes

Level 3 Expert

5391 Answers


Level 3 Expert

4369 Answers

Cindy Wells

Level 3 Expert

6164 Answers

Are you an Intermatic Hardware and Accessory Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides