Dome light help

[Alan]

My dome lights don't come on when I open either door. I think it's the interior lamp delay unit. I'd like help proving it.

When I open either door, the appropriate door lamps (amber/red door edge lights) come on. I have incandescent bulbs in original dome lights. If I switch either of them on at the housing, they both come on as they should. The glove compartment light works as it should.

I think all my symptoms point to one common point of failure between both dome lights not working with the doors. That's the interior lamp delay unit. Is there a good way to test it?

I want to replace it with Bitsyncmaster's unit and LEDs... but I want to troubleshoot the system first so I know it will work when I do.

As an aside, Bitsyncmaster's Dome Light Dimmer module has the warning that it requires LEDs that don't have a switching regulator. Can someone refer me to specific LEDs that are the right type to work with Dave's dimmer?

Thanks,
Alan

[81dmc]

Might be one of the three diodes in the driver's footwell and/or a ground wire broke off the female spade on the door plunger. I had a bad diode.

Once I get to my car, I will tell you what color wires to look at.

[Alan]

Thank you.

It seems the door switch wiring has to be good. Otherwise, the wiring for both would need to be bad and I'd think the door lights themselves wouldn't work.

I'd think the diodes for the door lights have to be good or they'd both have to have gone out at the same time.

The diode for the delay unit seems like another possibility, though.

Does my thinking seem correct? And then, how to determine if it's the delay unit or the diode?

[81dmc]

It's the diode then. I don't even have a dome light module installed.

BTW, door lights and dome lights run off different diodes.

[Bitsyncmaster]

The door lights will work with or without diodes. The dome lights will only work with good diodes from the door switches if the dome lights are set to "auto" position.

Do your dome lights work when you switch them to manually on? That could be forward or backward depending which way the dome unit is installed.

[Alan]

Do your dome lights work when you switch them to manually on? That could be forward or backward depending which way the dome unit is installed.

Yes, I just confirmed, the dome lights work manually, normally. If it helps, the door lights only work on their respective sides via their respective plunger switches.

[81dmc]

I may have an extra diode I can send you. I removed it after I reinstalled Dave's Idle ECU.

[Bitsyncmaster]

Check that the three diodes still have the wires attached. The diodes are by the drivers right foot in the harness.

[Jonathan]

Alan,

Did your dome lights work before as they were intended? Have you owned your car going back that long? Did you replace the light fixtures at some point?

The reason I ask is that I struggled getting mine working, with new fixtures or the old, until I realized the wiring is counterintuitive to how you think it should go between the "auto" and "manual" modes (with the doors and without the doors that is).

I had a thread discussing it at one point and I'll see if I can find it or the drawing that helped me sort it out.

[Alan]

Alan,

Did your dome lights work before as they were intended? Have you owned your car going back that long? Did you replace the light fixtures at some point?

The reason I ask is that I struggled getting mine working, with new fixtures or the old, until I realized the wiring is counterintuitive to how you think it should go between the "auto" and "manual" modes (with the doors and without the doors that is).

I had a thread discussing it at one point and I'll see if I can find it or the drawing that helped me sort it out.

I've owned it under a year. I've made no changes to the dome lighting. The door lights are LEDs now. The dome lighting is all stock as far as I know... but I don't KNOW the PO didn't do something.

The dome lights did work properly for a while since I've had the car. I don't recall for sure, but I don't think the dome lights started failing right when the door LEDs went in. Any possibility of a relationship there, though?

My next step is to see about the connections at the diodes. I'll need to find them first.

[Alan]

Ok. I found the diode bundle. Very easy. I did a visual and tactile inspection. Wires all seem connected. I moved the connectors a bit. All moved easily. I was hoping to "wear through" any mild surface corrosion. After all that, still no dome lights by opening the door.

Next step to test them? I have a simple multi meter. Look for high resistance one way and low the other?

Other recommendations?

[Bitsyncmaster]

Ok. I found the diode bundle. Very easy. I did a visual and tactile inspection. Wires all seem connected. I moved the connectors a bit. All moved easily. I was hoping to "wear through" any mild surface corrosion. After all that, still no dome lights by opening the door.

Next step to test them? I have a simple multi meter. Look for high resistance one way and low the other?

Other recommendations?

Yes, ohm test is open one way, very low the other way. Most multimeters have a "diode" range which reads the voltage drop over the diode, 0.7 volts one way, infinity the the other.

[Jonathan]

Alan,

Have a look at this post:

http://dmctalk.org/showthread.php?11960-Interior-dome-lights-can-work-with-LEDs-and-delay-unit-relay&p=174048&viewfull=1#post174048

It mentions the wiring changes I made.

You can also read much of the earlier comments that Dave coached me through, very similar to what you are doing with your diodes.

The dome lamps do wiggle out from where they are mounted fairly easily. Do so carefully though still as you don't want to snap a plastic clip or something on them.

[David T]

Check the wiring to the door switches, especially the two on the driver's side. If the wires are "crossed" weird things can happen. Then check the connections to each light. You may have then hooked up wrong. The diodes are the last thing to check. Pull the light delay module if you are using LED's.

[Alan]

...and bad diode takes it for the win.

There are three. I don't know if the colors are significant, but I have a red, black, and blue. The red and black were good. The blue show infinite voltage drop on the diode check and infinite resistance checking resistance (both directions).

Apparently I need a new Pektron A75-294.

Thank you, everyone, for all the help.

Thanks,
Alan

[DMCMW Dave]

You can replace that diode with a generic one from Radio Shack etc. Anything over 20V 1A is plenty. Solder the correct leads to the ends of the (the stripe end goes to the end that had the single line on the diagram on the bad diode housing), cover the whole thing in shrink wrap and plug it in. If you really want to get fancy make something up, then gut the original diode and RTV your new diode assembly inside the housing.

[Alan]

You can replace that diode with a generic one from Radio Shack etc. Anything over 20V 1A is plenty. Solder the correct leads to the ends of the (the stripe end goes to the end that had the single line on the diagram on the bad diode housing), cover the whole thing in shrink wrap and plug it in. If you really want to get fancy make something up, then gut the original diode and RTV your new diode assembly inside the housing.

Cool. Thank you.

[Alan]

So, Dave Swingle had a great suggestion. I opened up my diode housing because I wanted to see what was in it. I liked the idea of building a new diode into the diode housing. What Dave said to build is exactly what's in there; a diode soldered to 2 leads. I'd never seen a picture of one opened up.

It's 2 leads with a regular diode soldered in between, 2 halves of a cylindrical housing to hold it, and the outer housing. I cleaned it up, checked the solder joints, tested it, and it works. I just reassembled it, put it back in, and now I have dome lights again.

40927

[81dmc]

So it was just dirty? If so, it's pretty crazy how a little dirt/corrosion can effect the function of something like dome lights.

[Alan]

So it was just dirty? If so, it's pretty crazy how a little dirt/corrosion can effect the function of something like dome lights.

I don't have a good answer. The diodes are required for the circuit to work. One of mine failed the test Bitsyncmaster described. After opening it to rebuild it, it worked. I don't know why... except for possibly cleaning the contacts. All I know is that after, it tested good with a multimeter and my dome lights worked again.

[Peripatetic]

I think I have the same quirk on my car. Does your car have one "plunger" on each side or two?

[durech]

I tend to look for the simple solutions first. You said you did not know if the PO had changed the interior lights to LEDs out not. First thing I would do is just pull one of the lights and look. If they are LEDs, then try removing dimmer relay. That should make if work (although you won't have any dimming effect)

Sent from my Nexus 5 using Tapatalk

[Alan]

I think I have the same quirk on my car. Does your car have one "plunger" on each side or two?

I'm not 100% certain, but I think it's 2 plungers on the driver's side and one on the passenger side. I'll confirm later today and post my findings.

[81dmc]

There are two plungers on the driver's side and one on the passenger's side. One of the two on the drivers are for the buzzer, or in my case, the Cadillac door chime.

[Bitsyncmaster]

The use of diodes is to get logic circuits. The door logic needed was to have either door open to turn on the dome lights. The bad thing using diodes in a power circuit is you get a voltage drop of about 0.7 volts over each diode.

I've found the stock diodes can drop up to 1.0 volts so installing your own newer diode should keep that diode drop to 0.7 volts or less.

Now running the dome "timer" does reduce the dome light voltage drops so that is not important anymore in that circuit. The dome unit provides a parallel path for the dome ground current. If your running LEDs by just removing the dome "timer" your dome lights will only get about 10.5 volts.

[Alan]

There are two plungers on the driver's side and one on the passenger's side. One of the two on the drivers are for the buzzer, or in my case, the Cadillac door chime.

Yep. That's what I found, too.

How does the buzzer work? Key in ignition and door open? Car on and door open? I don't think mine works but I'd like to know how it should and why not. I do have 2 connectors on the switch that doesn't operate the door/dome lights.

[Peripatetic]

There are two plungers on the driver's side and one on the passenger's side. One of the two on the drivers are for the buzzer, or in my case, the Cadillac door chime.Well my theory is out. I assumed that since my car was missing the plunger and the dome lights didn't work when the door opened that they were related.

I wonder what the buzzer sounds like.

[content22207_2]

The use of diodes is to get logic circuits. The door logic needed was to have either door open to turn on the dome lights.

Actually the purpose of the diodes was to turn on only the door edge lights on an open door (versus illuminating both door edge lights when only one door was open). Normal cars have door plungers only.

You can bypass the diodes and the dome lights will still work normally, ie: dome lights will come on if either door is opened. Of course bypassing the diodes means door edge lights on both doors will also come on if either door is opened -- not a problem if you've got good condition outer door seals and edge sweep weatherstripping (illuminated edge lights on the closed door won't be visible).

If you do bypass the diodes, either remove the dashboard door ajar bulb (incandescent) or replace it with an LED bulb (acts as a diode) to prevent the battery from draining backwards from the courtesy light circuit through the instrument cluster via the door ajar indicator.

40969

If you are running incandescent bulbs in the dome lights, bypassing the diodes will make them burn brighter.

Bill Robertson
#5939

[81dmc]

I wonder what the buzzer sounds like.

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