Question about Intermatic Malibu 300W Power Pack Transformer ML300RTW

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My lawn lights stopped working, transformer tested ok. What could be the problem?

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You checked that power pack is getting electricity.
Scratch a wire across both terminal screws and see if there is spark.
If a bulb burns out, and is not replaced, additional power can burn out other bulbs.
Power pack should be unplugged if bulbs are not burning since that can burn out power pack.
Change out a couple bulbs and then plug-in power pack.
Check connections where lights tie into wire.

My power pack was doing same thing, I bought another power pack from Home Depot to check my lights. All but 2 bulbs were burned out. I replaced bulbs and returned new power pack.. and then power pack quit for good a month later.

I found tips to preserve power packs:
1) Match wattage of bulbs with wattage of power pack
-15 each X 20 watt bulbs = 300 watts, so install 300Watt power pack
2) Installing a 500W power pack on 300W of bulbs will burn out bulbs and power pack.
3) Replace bulbs as soon as they burn out or other bulbs will burn out and power pack will burn out.
4) When working on bulbs, unplug power pack or it may burn out.

Posted on Nov 14, 2010


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1 Answer

LG model MS3949CS/00 Not getting power to the HV transformer but all els works tested transformer HV cap and diode all ok.

did u check plug n internal my diode that went to earth was the culprit coz my microwave leaked into base and diode to stop leakage to earth had blown

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The timer on my 8100-0600-01 Malibu light transform is not working the on and test part work but I want to set the time on

The electronic dawn dust timers can fail easily in power surge etc.
Manuals, tips and troubleshoot resources on following link:

I recommend professional grade transformer for anybody wanting better quality and resistance to problems:

If you need further help, I’m available over the phone at

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Some power but not operating

Check out with a multitester whether the control panel switch on the power towards the high voltage transformer NNB disconnect the high voltage transformer for this test. if not the relay on the electronic controlle device is broken and the panel needs replacement. check also the 3 safety switches on the door for proper operation. mind the power it is dangerous.

May 10, 2013 | Sanyo Microwave Ovens

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The light on my unit does not light up. It was working anyway but now stopped. How can I tell if it is the transformer that is not working and not the motor.

You can take it to a pool supply store that works on robotic cleaners and they can test the electrical output strength of the transformer.

Jul 01, 2012 | Smartpool Nitro Robotic Cleaner and Caddy

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Our lights were all connected to one transformer, but the second half of the lights were dimmer than the first half. I installed a second transformer to help eliminate the dimming for the second half of...

1) Problem could be transformer voltage and/or length-and-diameter of wire.

2) Open following link for power pack resources including links to manuals, tips, trippers, instructions, and troubleshoot:

3) Unclear what is meant by 1st half and 2nd half of lights.
Do not connect transformers in parallel or series with each other.
Test across terminals A and B and see if it shows 12 Volts. If voltage is less, then power pack is not functioning correctly.
Power pack wattage must match total wattage of bulbs.
First bulb must be 10 feet away from transformer.

4) Use following chart for wire size:

5) Review resources above, and then add a comment for more help.

6) 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

Sep 05, 2011 | Malibu Hardware & Accessories

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I have a Watermill SS45DLV shower pump which has stopped working. Tested fuse (ok) . Tested power to transformer (ok) but not sure what voltage i should get at the pump pcb as it's not listed on the rating...

38v AC I think, similar problem here, check you have a circuit on the primary side of the transformer! If it's open you need a new transformer.

Oct 29, 2010 | Heating & Cooling

1 Answer

Malibu landscape lighting transformer problem

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:

May 30, 2009 | Intermatic Malibu 300W Power Pack...

1 Answer

Intermatic ML300RTW not working

Yes this loose strands is probably the issue, the Transformer is working too hard and shuts down. you can make sure by removing all the bulbs but the last one and turning the transformer on, if it fails- you've got bad wiring. move the x-former closer to the lights so you don't have very much bad wiring.

Apr 09, 2009 | Malibu Intermatic Inc. ML300RTW 300-Watt...

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