Dim Lights

Cyclonic

Seems like a dim subject, but this one has me a bit baffled, so maybe someone can enlighten me?

My 2012 T@B came installed with very standard RV 12v incandescent light fixtures.  Pancake lights.  They get so hot that they started to melt, so last summer I replaced two of them with LED versions of nearly the same fixture.





I replaced just the two that we use the most.  While very bright, they worked well.  I got two more later in the summer, but only recently got around to replacing them.  After putting the new ones in I have found that all of the lights are now very dim, and the older fixture still at the counter doesn't seem to work at all.

Fearing a short somewhere I have removed the new replacements, but I still have very dim lights.  I've checked the fuses, all good, and I am on shore power.  Ground looks good too.

Any ideas?

Dalehelman

What is your battery reading?

Cyclonic

13.2v, full charge.  That was after pulling the plug to the shore power.  Lights have the same issue on or off shore power.

Dalehelman

What is the voltage at the light fixture.

Cyclonic

I'll run a test when I get home this evening, have to dig out my voltmeter

Photomom

Can you post a link to the new lights?

Cyclonic

Well, problem solved.

Voltage at the lights read 9v.  I tracked to back to the converter, and found that while the fuse was not blown, it was weak, so power was not getting through.  Replaced the 10amp fuse and I was back in business.

@Photomom , these are the lights I got, though I don't think I paid nearly that much.  These are very standard in a lot of RV's, but they haven't used them in T@Bs in years now.

wizard1880

Nice find!  Wow that would send even seasoned pros on a scavenger hunt.  I'll bet the fuse was heating up somewhat when the lights were on from that resistance

Michigan_Mike

Photomom said:

Can you post a link to the new lights?

Found them on EBay for a reasonable price.  

ScottG

@Cyclonic, ok, I'll bite...  How did you determine the fuse was weak? Measure the resistance? Trial and error? I know a bit about wiring, but I agree with wizard1880 that this would have been a head-scratcher!

Photomom

If you didn't throw the fuse out already, would you please measure the resistance with an ohmmeter and let us know the reading? This is a new one to me.

Photomom

After thinking about this, I think the most likely cause is corrosion on the fuse blades or on the fuse holder itself. This could increase the resistance of the fuse assembly and cause a voltage drop. If that's the case, when you put the new fuse in it would have rubbed away some of the corrosion and made better contact.

You might inspect all of the fuses and fuse holders for signs of corrosion.

ericnliz

@Photomom, A little dab of dielectric grease works every time for ALL plug-in electric connections. Been using it for 40+ years, hasn't failed me yet!

Cyclonic

ScottG said:

@Cyclonic, ok, I'll bite...  How did you determine the fuse was weak? Measure the resistance? Trial and error? I know a bit about wiring, but I agree with wizard1880 that this would have been a head-scratcher!

Tossed it already, so I can't test it, but basically, when I removed the fuse this time I took a closer look at it.  Normally, when these things blow you know it, the circuit in the middle is very clearly broken.  This one it was not, but near the bottom of it it was considerably thinned out with a little bit of scorching.  So I am thinking it had started to blow, but not completely blown out, so some power was getting through.  All very odd, and I don't think I could make it happen again if I tried.

Photomom

I've never seen it but there is a rare failure mode that can cause a fuse to behave like that. Good job troubleshooting this. 

Photomom

BTW I always check suspect fuses with an ohmmeter unless they are clearly blown.