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I have, as the title says, a mighty weird issue. The dome lights do not turn ON which isn't a rare problem, but read on for the weird part.
The lights themselves are fine and light up nicely with 12V applied from a bench power supply.
OK, so I took out the dome assembly and moved the garage door opener out of the way and I saw that basically it is a brain-dead 12V feed from a nearby connector with some ground wire too and a switch which opens or closes the contacts to the metal terminals which hold the bulbs. There is no electronics there - just simple wiring and a trivial SPST sliding switch. The two bulbs are wired in parallel. The contacts inside look rusty but the terminals holding the bulbs are shiny.
So I thought, sure, this is a fuse issue. Except fuse 19 controls other lights too and these come on.
So then I though to check the bulb terminals to see what voltage the bulbs are getting. When the bulbs should be ON, the terminals get 2.58V (yes, not 12V). The fact that they get some non-zero and very repeatable voltage tells me that the fuse is probably OK, as expected. But the voltage makes no sense and there seems to be not enough voltage applied to drive the bulbs. Moreover, once the bulbs are inserted I see the voltage across the bulb at 0V which tells me there is no current sourcing capacity. Whatever is providing that 2.58V is not a real power supply. Could be a diode forward voltage somewhere? A bit high for a silicon diode but not uncommon in general. Is that it?
Any hints or thoughts or suggestions? I am not relying on these lights but would love to get the circuit to work again.
I had my driver side dome light not coming on last month. My problem was the current not going through a wire to a metal part that holds the light bulb.
The wire terminal ends and the bulb holders are secured by rivets. The rivets and other metal parts were not making good contacts.
I used a spring loaded center punch to tighten rivets so they will make better contacts.
This trick worked on my car. The dome lights light up every single time they are activated. I think they are brighter than when I got this car in October.
Hope this will help.
The rivets are the most likely culprit. I've had to fix mine a couple of times (each time a different rivet). They don't take solder very well, unless you have good equipment and really know what you are doing. I wound up replacing one of the rivets involved. I like TCMMark's idea of using the punch except for the fact that old plastic is involved. I was concerned about breaking the plastic housing. They use fairly standard rivets, I did a write up about that a while back and can look it up if you need it. Let us know how it turns out.
The rivets are the most likely culprit. I've had to fix mine a couple of times (each time a different rivet). They don't take solder very well, unless you have good equipment and really know what you are doing. I wound up replacing one of the rivets involved. I like TCMMark's idea of using the punch except for the fact that old plastic is involved. I was concerned about breaking the plastic housing. They use fairly standard rivets, I did a write up about that a while back and can look it up if you need it. Let us know how it turns out.
You have to use an appropriate size drift punch to support the work. Drift punch is securely clamped on a bench vise and take the blow of the punch action.
OK, so I have a long post to make. First off, now that I know what the problem was, I have to apologize because nobody here could have helped, really. I do appreciate the suggestions though.
So... the story starts with me installing a dashcam. I asked in another thread and was told where to get the power without routing it from afar: the harness for the interior rear view mirror. So that's what I did. I tapped into the power and ground, added a USB power supply:
and thought I was done.
Except that the dashcam in question was a power hog and affected the other components on the circuit (in this case fuse 22). And no, fuse 22 did not blow, but the other major power hog on that circuit - the antenna motor - started doing something weird when the radio was on. I mean, yes, it is supposed to moved the antenna but in this case it somehow redistributed the load and started drawing too much off the other fuse it sits on - fuse 19. Now fuse 19 did blow and this caused all my troubles.
But wait, didn't I start this thread with saying fuse 19 was OK? Yes I did. Turns out this is a one in a million case where the fuse blew but it also checked out fine when pulled out. It happens but I almost feel like I lost a lottery. Once I got frustrated enough and actually replaced the fuse for a new one that other fuse blew up as it should. Now the good news for me is that I have been meaning to disconnect the antenna motor for a while but got lazy. So five minutes after I saw the light the antenna motor was unplugged and all circuits are now happy.
And finally about them rivets. I pulled out the connectors altogether with pliers Those rivets are not very strong and did not look very reliable. I then screwed in and soldered in 1156 sockets:
The whole thing barely fits but it sure produces tons of light. When I do an overhaul, I do an overhaul.
BTW I also ripped out the rear view mirror once I understood how it mounted to the windshield. What a piece of crap that mirror is: bulky, yet it provides no coverage of blind spots and it is hard to mount clip-on mirrors on because they are just not big enough to obscure the mirror they clip onto. As a result the look of the whole thing is just terrible with clip-on mirrors. In its place I put a custom mount and an ATV mirror:
I did lose the wireless receiver in the process and so pretty soon I will install Advanced Keys to get everything better than OEM. Also waiting on my VAIS to arrive so I can get the I Agree screen out of the way so I plan on doing a lot of the front electronics gutting and rewiring a bit later. I might bug you fine folks again if I screw something up
Thanks again and happy new year.
12-23-20, 05:46 PM
Dome light - weird problem
Those rivets are not very strong and did not look very reliable. I then screwed in and soldered in 1156 sockets:
