Pool light went dim, then out; now replacement is dim

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rhythm

LifeTime Supporter
Mar 1, 2008
124
Lake Forest, CA
It appears that I have a pool light issue that seems a bit strange (to me, at least). Our pool was completed about 5 years ago, and earlier this Summer I noticed that our main pool light, a Pentair Amerlite, was getting dimmer. This seemed strange to me...I figured the failure mode would simply be no light at all. Over the course of a week or two, the light continued to look dimmer, then finally was completely dark. I opened up the panel of the control center (Jandy Aqualink) and confirmed that 120V was getting to the pool light side of the relay that it's on. This light didn't have a very high number of hours on it, but I figured some things fail earlier than expected, so no big deal.

Anyway, I went ahead and replaced the bulb and gasket. Everything seemed OK with the fixture...no signs of corrosion anywhere, no signs of leaks (it was completely dry inside where the bulb is housed). After replacing the bulb, everything seemed to be working fine and I figured I was done. Well, after only 4-5 weeks of having the new bulb in there, I'm noticing that the light is getting dimmer again! I noticed this a couple of nights ago, and I think it was a little dimmer again last night. So obviously something is not right. The spa light, which is on its own relay, is still working just fine.

Can anybody give me some suggestions as to what should I be looking at to try and figure this out?

Thanks,
Greg
 
Thanks for the replies.

John, I'll try connecting the pool light to the relay that currently connects to the spa light, and see if the bulb is brighter again. I have a feeling that the pool light bulb has already degraded, based on what happened with the previous bulb, so it might stay dim now no matter what, but I'll try it. I probably won't connect the spa light to the relay that currently controls the pool light though, just in case there is something with the relay/circuit that is causing the pool light bulbs to burn out prematurely. I don't want to damage the spa light also.

Dalandlord, I agree with you about the load/no load idea. When I checked last time and read the 120V, the pool bulb was connected, but the bulb had already gone completely dark, so there was probably no load at the time. I'll measure the voltage at the light (with it turned on) when I get home today and see what I get. The strange thing is, though, is that the new light was plenty bright for a while after I first installed it, then went dim after several weeks. I would have guessed that if the pool lights are loading the relay/circuit to where it can't supply the proper voltage, the new light would have been dim right away.

It seems like the light bulbs are truly degrading and going bad, rather than just not getting enough power. I say this because of the fact that the new bulb was nice and bright after being installed, rather than being dim or dark immediately upon installation.

Anyhow, I'll check things out and report back.

Thanks!
Greg
 
OK...here's what I found after work today....

With the pool light on (it's pretty dim now) I measure a full 120V (122V actually) on the pool light side of the relay.

With the pool light on, I measure nearly zero resistance across the relay (same as when I measure the spa light relay resistance).

When I move the wire for the pool light over to another relay and turn that relay on, the pool light is still dim. I figured that might be the case, though, because I believe the pool light is degraded.

Normally, these results would have me believe that the whole problem is the light bulb. But since the bulb is new and this same thing just happened with the previous bulb, I'm still thinking that something else is causing the issue.

The breaker for the lights is probably OK, because the spa light is on the same breaker and it's been fine. Is there anything else about the relay or the light fixture itself that needs to be checked out for problems?

A couple more things I'll mention:
Ever since we've had the pool I've noticed that there's normally a bit of a delay when switching the pool light on manually (I press the button, and a second or so later the relay clicks and the light comes on.) The spa light relay has not done this; it clicks shut immediately upon pressing the button. Even so, the first light worked fine for nearly 5 years before it began dimming. So it seems more like something has happened more recently to cause the issue.

When I replaced the bulb, I replaced a 400W bulb with a 500W bulb. But I believe the fixture and wiring are made to handle a range of wattages up to 500W on the Pentair Amerlite.

Thanks for any suggestions!
Greg
 
Unless there is something different about pool bulbs I don't know about it is very unusual for an incandescent bulb to dim like that instead of just going out. For two of them to do that seems like it must be more than a coincidence. I just have no clue what could be causing it. Hopefully Someone here has seen it before.
 
rhythm said:
OK...here's what I found after work today....

With the pool light on (it's pretty dim now) I measure a full 120V (122V actually) on the pool light side of the relay.
Click to expand...

Are you measuring to the neutral line feeding the light or to ground in the box?
 
It sounds like there is some sort of excess resistance in the lines somewhere. Here are some suggestions:

1) Make sure that the contacts in the light fixture are clean and making good contact.
2) Check the connections in the junction box.
3) Measure voltage at the bulb with the light on.
4) Measure the resistance of the power and neutral wires from the relay to the light bulb socket.
 
John T, I'm measuring between line and neutral. I did go ahead and measure between line and ground, and it was nearly the same measurement.

Dalandlord, I'll probably be taking the pool light fixture out of the pool this weekend to inspect it, so I can try that. The previous bulb appeared completely dead when I replaced it, and I have a feeling this one has degraded to being dim no matter what, but it's certainly worth checking out.

James, it does seem like something's wrong somewhere for sure, but what's so strange is that the first bulb went dim, then nothing, but when I installed the new bulb it was fully bright for a few weeks before the dimming started. Intuitively I would have thought that the new one would have been dim right off the bat if I have an electrical problem, but I guess I must have something going on that degrades the bulb over a short period of time. I'll check the contacts in the fixture this weekend when I take it out. I looked in the junction box, and everything appeared fine upon inspection, but I haven't unscrewed the wire nuts yet. This weekend I'll have to rig up a long wire from the relay contact that I can take over where the light fixture will be before I can make the last measurement that you suggested.

Tonight I measured the voltage across the relay contacts with the light on. There was only about 13-14 millivolts, so real drop there. The voltage across the spa relay was only 3-4 millivolts, but it's also only drawing 20% of the current that pool light is, so I think this is OK.

Something that I thought was strange, but perhaps it's normal: When none of the relays are closed, I get continuity between the pool light load side of its relay and the spa light load side of its relay. The resistance varies between 5 and 25 ohms between the pool light and spa light lines (that go over to the junction box then to the lights). I thought these two wires would be completely isolated. However, when one relay is closed, I do measure a complete open between the two lines, so perhaps it's fine.

Thanks for all the comments...this is weird....I'll keep at it.

Greg
 

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It sounds as if it is one of two things: degraded light socked with oxidation built up on center terminal (this oxidation could have been broken down somewhat with light change, but it may be that the center terminal of the Edison fixture is not making good a connection with the bulb's center contact; e.g. the resistance between the line and neutral wires is high) or that there is a short somewhere along the cord to the light, or in the fixture (e.g. the resistance is very low). Does this fixture have a thermal protection circuit? That could also be the culprit.
 
Craig,

I'll be checking all of this out in better detail over the weekend. I'll be removing the wire nuts from the connections in the J-Box so I can do some checking with the fixture wiring separated from the J-Box to Relay Box wiring. I'll also be pulling the fixture from the pool onto the deck so I can make measurements at the fixture, check the oxidation, remove the bulb and see if it fully lights or not with another power source, etc.

Yes, the pool light circuits are GFCI protected. I don't know if the fixture has a thermal protection circuit, but I should be able to easily find out, since it's a very common fixture (Pentair Amerlite).

Thanks for the suggestions....I'll report back once I've done more testing.

Greg
 
JamesW said:
It sounds like there is some sort of excess resistance in the lines somewhere. Here are some suggestions:
.....
3) Measure voltage at the bulb with the light on.
Click to expand...

Just want to make sure I understand. When you say "with the light on" you don't mean that the bulb is installed do you? I need to have the bulb removed to get to the + (or 'hot') when I'm measuring the voltage, right? Or is there a way to measure the voltage at the bulb with it actually installed?

With the bulb removed, I take it that the center contact at the bottom of the socket is 'hot', and anywhere on the inner wall of the light socket is neutral? Any safety precautions when doing this that might not be obvious?

Thanks,
Greg
 
No, take out the light bulb and with the wiring all connected, check the voltage between the center and sheath on the Edison socket. You should be getting 120V (this is a standard 120V line, right?). Also, check the resistance (with the circuit off and the light cord disconnected from the panel wires in the pool light junction box) with the bulb in between the neutral (white) and load (black) wires going to the light. Then, take out the pool light bulb and check the resistance. You should probably set your meter to read in the 1-2kOhm range for this.

What values do you get? If you are getting low voltage, and the resistance is high, you have a defective circuit and will probably have to replace the unit.
 
rhythm said:
Just want to make sure I understand. When you say "with the light on" you don't mean that the bulb is installed do you? I need to have the bulb removed to get to the + (or 'hot') when I'm measuring the voltage, right? Or is there a way to measure the voltage at the bulb with it actually installed?
Click to expand...
I was thinking that you might be able to use a light socket plug adaptor such as this:

398px-Light_socket_plug_adapter.jpg
 
OK...a few measurements that I just took...

With everything connected, powered up, and the bulb out, I measure exactly 120V (120.3 actually) between line and neutral at the fixture socket.

Next, measuring between the black and white wires from the light fixture, disconnected at the junction box, the resistance is wide open with no bulb in (as if the leads weren't touching anything at all). With the bulb in, I'm reading 2.5 to 3 ohms (remember, the bulb is already heavily degraded). If I measure between tip/sleeve on the bulb itself (not screwed in to anything) I get the exact same 2.5 ohm reading. I believe this agreement between resistance readings confirms that the light fixture hot/neutral resistance is indeed wide open. As another check, I grabbed a 100W bulb from a lamp and screwed it in to the pool light fixture. I measured 11 ohms between the black/white wires at the j-box. And again, this matched exactly with the measurement made with just the bulb itself (11 ohms between tip/sleeve).

Is the resistance between hot and neutral on the fixture supposed to read wide open?

Also, in the j-box, I didn't disconnect the ground wire from the light fixture to the ground bus bar. Should I do this and measure between hot and neutral again, or does it make no difference?

Thanks,
Greg
 
rhythm said:
Is the resistance between hot and neutral on the fixture supposed to read wide open?
Click to expand...

With the bulb out, yes. You should see close to zero from neutral to ground. They are connected at the panel.
 
Hi John,

I'm don't think I understand the connection between the question of mine that you quoted and the statement that you made. I'm measuring an open (infinity) resistance between hot and neutral at the j-box (the light fixture side), with both of those wires disconnected from the wires from j-box to panel. So I'm not sure how the ground to neutral connection at the panel influences me reading an open between hot and neutral at the j-box.

Of course, this wouldn't be the first thing that I don't understand!

Greg
 
rhythm said:
Hi John,

I'm don't think I understand the connection between the question of mine that you quoted and the statement that you made. I'm measuring an open (infinity) resistance between hot and neutral at the j-box (the light fixture side), with both of those wires disconnected from the wires from j-box to panel. So I'm not sure how the ground to neutral connection at the panel influences me reading an open between hot and neutral at the j-box.

Of course, this wouldn't be the first thing that I don't understand!

Greg
Click to expand...

I was just giving extra info. Hot and neutral are isolated except at (in) the load. Ground and neutral aren't isolated.
 

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