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AssuredElectrical, Master Electrician
Category: Electrical
Satisfied Customers: 4241
Experience:  Contractor-42+ Years in the ElectricalTrade
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I have 2 security lights on my garage. After dusk, one will

Customer Question

I have 2 security lights on my garage. After dusk, one will blink on and off continously. They both work fine in test mode during the day. They are both on the same circuit and one works fine. I replaced the sensor with a more expensive one with no change. The garage opener is on the same circuit but doesn,t interrupt the other light. I tried running another line to it (just to try anything possibility) and it didn't work. I put them on separate switches also. Please help if you can.
Submitted: 1 year ago.
Category: Electrical
Expert:  AssuredElectrical replied 1 year ago.

Welcome. My name is ***** ***** would be glad to assist.

Need some more details on the situation.

1. Is this a new installation?

2. What is the location of each fixture?

3. What type of bulbs are in the fixtures?

4. Make and Model of the fixtures?

Let me know and we can continue,


Customer: replied 1 year ago.
It is not a new install. I purchased the home in 2010 and both lights worked until last fall when one went the way I described. One fixture ( the errant one) is on the front of the garage and the other is on the side of the garage, about 10 feet away. I tried both flood and replaced the fixture and tried halogin, same outcome. I dont know the make of the older sensors (Standard Home Depot style) but the new one is All-Pro MS180W.
Expert:  AssuredElectrical replied 1 year ago.

Ok, thanks.

With motion sensing security lights, there are a few items that can have effects on them.

It will be one of them and it takes some work to find which one.

1. Keep in mind, the so called "test " modes only check the motion capabilities of the sensor in the daylight

It does not use the daylight sensing part, so it changes when it is dark many times form what the setting is.

I never complete testing unless it is dark. The test mode allows close proximity.

2. Another light in the area can put enough light on the sensor and cause it to malfunction

3. Bulbs in the fixture itself can cause the same issue, the sensor picks up enough light to trigger

4. Anything in the zone of the sensor, can trigger, whether it be a leaf, tree limb, flag or other item that disrupts the path.

5. A bad sensor of course can cause the same issues

6 Having bulbs over the rated wattage of the fixture and sensor will cause issues until it finally burns out the sensor

7. Loose connections in the wiring or in the fixtures bulb sockets.

8. Loose Bulb socket rivets or solder will cause issues (each socket has either rivets or solder connections)

9. Low voltage on the line when the fixture is operating

Always best to start with positioning the sensor differently, little by little.

Then the bulbs positions on all fixtures in the area

Those are the items to inspect and check.

Sometimes it takes a while to find that needle in the hay stack.

Customer: replied 1 year ago.
Ok. I've looked into and tried all but number 9. Do you mean the low voltage like from the garage door opener? The fixture that isn't working is on the front, above the garage door. If so, if I unplug the garage door opener will that tell me anything? The door opener was there when we moved in and both lights worked then. I do have some shrubs next to the garage ( they were there when we move in also) so I put a large piece of cardboard in front of it for the night. Didn't help. I'll try the test mode at night. I guess #9 is the question.
Expert:  AssuredElectrical replied 1 year ago.

Ok, it shows you in the USA, so where is is dark in the USA now to check all of the items, out of curiosity?

Low voltage is just that lower voltage than the regular 115 volts supply.

You have to measure the voltage at the fixture to determine.

Using cardboard is not the way to test, it will generate a flicker and the sensor will see it.

DO NOT use the test mode at night, it is of NO value at all.

I thought the explanation was sufficient on the previous post, maybe it wasn't clear on how it works.

Customer: replied 1 year ago.
I have tested during the day and all worked well. So that's out. I will test the voltage at the light. I have put a small refrigerator ( dorm size) in the garage. Could the load draw (when the compressor starts) lower the voltage enough to start the light blinking?
Customer: replied 1 year ago.
I forgot to answer your question. It is 3:45 pm here now. and will be dark in 3 1/2 to 4 hours.
Customer: replied 1 year ago.
I tested the voltage when the compressor in off and when it kicks on. It went from 119.8 to 119.6 and right back again.
Expert:  AssuredElectrical replied 1 year ago.


The voltage is a rarer issue and usually caused by loose connections.

I was trying to see how one could go through and do all the tests in daylight when the testing I posted is all at night.

Except for the inspection side and that would take about an hour to 1 1/2 hr to check by a good electrician.

Your voltage numbers are good that you measured, I would say it is not an issue if taken when the lights are all on.

Customer: replied 1 year ago.
Well, I will start over again. I will put the halogin fixture back on, so there is no doubt that the light won't mess up the sensor. Then test it during the light hours in test mode. While in test mode and the light is on, I will test the voltage when the refrigerator compressor comes on. All connections will be checked. No cars in the driveway, in case of reflection. All other lights will be turned off. I will let you know as soon as I can as to what happens. If this doesn't work, you are suggesting that I hire a good electrician, correct?
Expert:  AssuredElectrical replied 1 year ago.


If you carefully inspect and perform all the tests with everything posted, you should find the issue, no need for anyone else.

The list covers it all.

Not sure what the posting of halogen fixture back so it doesnt mess with the sensor? Halogens are notorious for their light output. So you have to be sure of their direction.

The only bulbs NOT to use are LED and CFL unless the motion sensor instructions state they are allowed.

Also, set your sensitivity to approx 40-50%.

Customer: replied 1 year ago.
The halogen is what was on it originally and the case it's in deflects the light away from the sensor. I don't think the light had much bearing on it because as soon as it went into night mode, the light started flashing. It didn't even wait to be set off by movement.
I've gone through all of the changes. Set up the field with the test mode and checked all of the connections both in the light junction box and where the wires come in. It is set at about 40 to 50%.
Fingers are crossed and a drink waiting in the frig to celebrate
I'll let you know how it went.
Thank you
Expert:  AssuredElectrical replied 1 year ago.

Ok, very good.