Interior dome lights can work with LEDs and delay unit/relay?

[Jonathan]

I recently replaced a faulty rear interior dome light fixture with an aftermarket replacement from DMC. I reinstalled the LED bulb I had for it with the new fixture and it works. It will only come on when you tilt the lamp one direction and not the other though (same thing with the front light fixture).

The wiring diagram for the interior/door lights shows the always on wire coming from fuse #12 and this is the power source which allows me to turn on the interior light manually. They do not come on though with the doors being open as shown going through the "delay unit" or relay #25. I don't have a relay #25 in place as it was pulled sometime ago. I don't remember why really, other than it was related to not having the dimming feature if you go with LEDs in the dash. I do have a dimming feature through the rheostat for my instrument cluster bulbs (never changed to LEDs) and my HVAC panel bulbs might have been changed to LEDs, I don't really remember at the moment.

Can someone explain how that delay unit/relay was intended to work with the dome lights or dash lights and what my options are to make it work again, with or without LEDs? I imagine I have the correct relay to put back into that #25 spot in a box somewhere if needed. As for now, the dome lights have LEDs in them and so do the six door lights. I think that is it though.

[mluder]

I recently replaced a faulty rear interior dome light fixture with an aftermarket replacement from DMC. I reinstalled the LED bulb I had for it with the new fixture and it works. It will only come on when you tilt the lamp one direction and not the other though (same thing with the front light fixture).

The wiring diagram for the interior/door lights shows the always on wire coming from fuse #12 and this is the power source which allows me to turn on the interior light manually. They do not come on though with the doors being open as shown going through the "delay unit" or relay #25. I don't have a relay #25 in place as it was pulled sometime ago. I don't remember why really, other than it was related to not having the dimming feature if you go with LEDs in the dash. I do have a dimming feature through the rheostat for my instrument cluster bulbs (never changed to LEDs) and my HVAC panel bulbs might have been changed to LEDs, I don't really remember at the moment.

Can someone explain how that delay unit/relay was intended to work with the dome lights or dash lights and what my options are to make it work again, with or without LEDs? I imagine I have the correct relay to put back into that #25 spot in a box somewhere if needed. As for now, the dome lights have LEDs in them and so do the six door lights. I think that is it though.

I can't comment on the interaction with LEDs however I can talk about functionality.

The interior dome lights have a delay feature that keeps them illuminated for 5 seconds or so after you close the door. They then will slowly dim to off. Most of the dimming units have failed as they eventually lost the ability to hold the charge required to illuminate the lights once the switch in the door was off. Mine will not work when I open and close the door... however if I open it, close it, and then open and close again quickly after the first cycle, mine works.

Modern replacement? I believe Bitsyncmaster on this board was offering a digital version though I'm not sure if he still has them or if they work with LEDs. Knowing his work, I bet they do.

Cheers
Steven

[DMC5180]

BITSYNCMASTR still offers the digital dome light unit. It works with both LED and standard bulbs. It is also programable.

[Bitsyncmaster]

I still have some of my dome units in stock. Yes they will work with LEDs or incandescent bulbs in the dome lights. You can not have any of the switching type LED regulators installed or it will mess up the way the logic works in my unit. Installing my unit requires some wiring changes so check my web page to see if you can do those changes.

The OEM dimmer unit did dim the dome lights with incandescent bulbs. It would not work with LED in the dome lights and would even leave the dome light dimly lit.

[Jonathan]

I had forgotten that one thing was related to the lights delaying when turning off and the other was them dimming with the rheostat. Thanks for the explanations.

My LEDs originally came from DMC not long after getting my car, so I don't believe I would have any trouble with what is mentioned on the SuperBright style ones. I looked back at some old photos when I first got my car and it looks like I had one of the OEM delay units (white in colour and a bit taller than the other relays beside it) and must have removed it.

Dave, do you have prices somewhere for your products? PM me if you'd prefer. I'd like to know how much the delay unit one is as well as the individually fused (painted blue) fan fail module (assuming you still have some of those in stock as well).

[Bitsyncmaster]

I have plenty of stock except for the dome unit and Specialty relays are built to order. I've been waiting to place another circuit board order for the dome units.

Fan Fail, $94
Dome unit, $88
RPM relay, $83 with your old unit
Fan relay, $77
Blower relay, $72
Head Light relay, $72
Hot Start relay, $66
Pair of window switch LED boards, $20, $25 installed, requires the new DMCH switches.
Idle ECU, $138 with your old unit. I have 11 pin units also for $150 with your 9 pin unit returned.
LED AC panel, $110. Your choice of blue or green backlighting.
Front Relay Bank Ground Buss, $15. $10 if combined with another product.

Prices include shipping to lower 48 states

[Elvis]

That's exactly how it is supposed to work.

it sucks from the beginning, but the schematic says it is built this way.




I can't comment on the interaction with LEDs however I can talk about functionality.

The interior dome lights have a delay feature that keeps them illuminated for 5 seconds or so after you close the door. They then will slowly dim to off. Most of the dimming units have failed as they eventually lost the ability to hold the charge required to illuminate the lights once the switch in the door was off. Mine will not work when I open and close the door... however if I open it, close it, and then open and close again quickly after the first cycle, mine works.
...

Cheers
Steven

[Jonathan]

Update/photo added:

(I have been getting some good progress with Dave's help via PM recently, but needed to add a photo, so I came back to the original thread. I'll circle back here with an update to summarize the troubleshooting and understanding shortly).

In checking the diodes under the driver footwell near the gas pedal, they look like this:

3472134722

They were initially wrapped in some electrical tape to keep them neat and together with the larger wire jumble. I got them unwrapped and they looked okay physically and the connections seemed ok. I had the battery disconnected and connected/unconnected/connected/unconnected each end to see if the metal tabs were ok and that seemed fine but no change in the dome lights.

(Basically, my front and rear dome lights work fine in the manual mode but not the auto mode with the door switches. I did test my door lights to see if each side would turn on or off only with that particular door switch and that aspect worked. The dome lights just don't want to come on with power supplied by the purple/white "door open" mode.)

I took each diode out and tested with a multimeter. I have an Ohm mode on the meter which includes a diode symbol but not a dedicated diode only mode. Each diode tested out consistently with open loop in one direction and resistance in the other. The values I got for resistance were:

Red diode: 0.8 Mohm
Black diode: 11.5 Mohm
Blue diode: 10.2 Mohm

My meter usually works ok in auto ranging itself for higher or lower magnitudes of measurements, but I'm not sure what this high resistance reading is telling me? It was "Mega" ohm, i.e. one million ohms, which doesn't seem right to me.

So, one thing I was wondering is whether the colour of these diodes matters like it does with our fuses, or whether it doesn't. There aren't a pile of markings on the diodes to interpret unless I missed something.

Also, if they are different sizes by chance, is it going to matter which one goes where? On the schematic they don't differentiate, not that I can see anyway.

Where does one get replacement diodes if I were to need some? Does a modern Radio Shack/Source sell this sort of relic still or can you buy these individually from DMC like any other part? EDIT: Are these what I may need if indeed mine are shot? http://store.delorean.com/p-7181-diode-1-ampa75294.aspx

[Jonathan]

Red diode: 0.8 Mohm
Black diode: 11.5 Mohm
Blue diode: 10.2 Mohm


Ignore those. I realized I wasn't using my multimeter properly. I retested with the correct mode and got all three diodes in at between 0.55 volts and 0.57 volts.

I may dig into the relay/fuse area a little bit thinking perhaps one of the connections on the underside of the relay unit socket (#25) pushed through or came unattached or may just leave it as is and consider it good enough.

[Bitsyncmaster]

Your photos of the diodes look good. One connector on the black diode those two wires should be purple with a pink stripe but it would not be the first time our wire colors got changed.

You meter readings of about 0.6 volts (diode test) would indicate the diodes are good.

So now I'm thinking your dome lights are wired wrong. Can you post a photo of each dome light wiring?

[Jonathan]

So now I'm thinking your dome lights are wired wrong. Can you post a photo of each dome light wiring?

I don't have them hanging down right now and no previous pictures of the wiring. I'd pull them down but not keen on snapping the plastic trying to pry them out again.

The wiring behind was not terribly complicated. A black ground and then the two power wires. One of them being purple (always on) and the other being purple/white. I have the lights working with the always on power, which to me says the ground is where it needs to be. Would those two power tabs on the light fixture care which one you gave to the always on power and which one you gave to the switched power? It didn't look like it would matter. Tilting it one way is manual on and tilting it back the other way is auto on. Is there anything more to it that you know of?

[Bitsyncmaster]

I don't have them hanging down right now and no previous pictures of the wiring. I'd pull them down but not keen on snapping the plastic trying to pry them out again.

The wiring behind was not terribly complicated. A black ground and then the two power wires. One of them being purple (always on) and the other being purple/white. I have the lights working with the always on power, which to me says the ground is where it needs to be. Would those two power tabs on the light fixture care which one you gave to the always on power and which one you gave to the switched power? It didn't look like it would matter. Tilting it one way is manual on and tilting it back the other way is auto on. Is there anything more to it that you know of?

The dome lights only clip into the paper board. My car they almost fall out so I had to use some hot glue.

The switch common of dome lights goes to the purple wire. Not sure if you had it wired wrong what that would do. But maybe someone added some wires to get power to something else.

[Jonathan]

The dome lights only clip into the paper board. My car they almost fall out so I had to use some hot glue.

The switch common of dome lights goes to the purple wire. Not sure if you had it wired wrong what that would do. But maybe someone added some wires to get power to something else.

Ok, let me pull it down and take a picture. You've got me thinking maybe it is bass ackwards.

[Jonathan]

Here's the picture of the rear dome light. You're right, it did come out pretty easy. This is the replacement offered by DMC (aftermarket) and I think the original was a bit of a tighter fit AKA harder to get out.

34729

Does the way I have this wired look okay? I didn't have anything to go by initially, but chose to do it this way because the far end where the ground is didn't look like any other connections went to it and figured each of the power sources had to have the ground on the far end to make it work. That left the two remaining tabs for the power wires, and I figured it didn't matter which one was which (tilt forward or tilt backwards).

I can change it really easy if you see something that needs changing.

[Bitsyncmaster]

Here's the picture of the rear dome light. You're right, it did come out pretty easy. This is the replacement offered by DMC (aftermarket) and I think the original was a bit of a tighter fit AKA harder to get out.

34729

Does the way I have this wired look okay? I didn't have anything to go by initially, but chose to do it this way because the far end where the ground is didn't look like any other connections went to it and figured each of the power sources had to have the ground on the far end to make it work. That left the two remaining tabs for the power wires, and I figured it didn't matter which one was which (tilt forward or tilt backwards).

I can change it really easy if you see something that needs changing.

I don't think that is an OEM dome light. My OEM units have the common on one end (one terminal) and the other two terminals on the other end. The common (always connected to one end of the bulb) should have the purple wire. I've also seen some replacement dome lights that have a diode on them. On those the diode needs to be shorted.

[Jonathan]

I don't think that is an OEM dome light. My OEM units have the common on one end (one terminal) and the other two terminals on the other end. The common (always connected to one end of the bulb) should have the purple wire. I've also seen some replacement dome lights that have a diode on them. On those the diode needs to be shorted.

You're right Dave, it isn't an OEM light fixture. It is this one:

http://store.delorean.com/p-10545-lamp-assyfrt-rear-int-aftermarket.aspx

It fits nice and is functionally identical according to the description.

So if I were to move the purple wire (always on power) to the end of the bulb which only has that one connection, is that you are referring to "common?" The end I mean is where nothing else connects to it but that one connection/wire. That's why I had thought that would need to be the ground, since, the way I see it, if you were tilted in one of the directions, you would have the purple/white on one end (the end that tilts) and the other end would be the purple wire. And no ground in play. At least that's how it seems to me.

Anyone able to clarify?

[Jonathan]

The common (always connected to one end of the bulb) should have the purple wire.

Well kudos to you Dave for knowing how to fix that problem!

I swapped the purple wire with the ground and put it on the common like you said. Reversed the direction of the LED bulb by 180 degrees and bingo, I've got dome lights now!

I think they are brighter than they were before too. Perhaps something to do with the current going the wrong way through that circuit maybe? Both dome lights (I changed the same problem on the front one as well) and they come on with either the doors while tilted in auto mode or in manual mode if tilted the other way.

Thanks again for your help on this. Cheers!

[Bitsyncmaster]

Glad to hear it's fixed.8)

[Kukem]

Hmmm, my Dome lights will only work in the always on position. The rear one works with the doors if it has an incandescent bulb in it, but not LED. The front one does not work with the doors period. I have my front one wired like Jonathan's picture and then switched the purple and black wires and still nothing. Tried it with both types of lights and it just does not work with the doors. I also ended up breaking a tab off on the back one trying to put it back in. :(