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Interior Lights Brain Teaser

 
Old 02-22-2019, 12:43 AM
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Default Interior Lights Brain Teaser

Vehicle is 1988 S4 with Interior Light Delay Relay and no Alarm.

Confirmed all 5 light positions (Doors, Over mirror, Dome Light and Hatch Light) turn on when manually switched ON.
Confirmed all 5 light positions turn on when hatch is opened
No reaction from lights when either door is opened.

I removed the switches in door jamb, cleaned the switch and thread hole with brass brush and deoxit 5.

No improvement. I loosened passenger side door jamb switch and attached a jumper ground wire to it. No change but Interior Light Delay relay made crackling or rapid clicking sound.

Removed jump wire and screwed non compressed plunger switch back on passenger side. As it grounded out, relay started making sounds again.

I think the relay is done but that does not explain why the rear hatch works to instantly trigger lights UNLESS it isn't part of the Interior Light Delay circuit.

Help appreciated!
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Old 02-22-2019, 01:40 AM
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So I found this other thread where the pins of the Interior Light Delay Relay are described...

Pin - Function
==========
31 - Ground (needed)
31L - To interior lights (needed)
T/TK - Negative trigger from door pin switches (needed)
30a - Power for higher relay functions (optional)
15a - Ignition - truncates delay with ignition on (optional)
31Z - Negative Lock - truncates delay when locking (optional)

Could I remove the relay and jumper T and 31L to just work without a relay?
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Old 02-22-2019, 12:07 PM
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I read a comment like "jumpering T/TK and 31L puts alot of load on the lights" and it might not be good long term.

If that is the case, would the below Relay scheme work with a standard 53 relay?


The goal would be to trigger the relay to switch on off the ground but I'm not too swift with this stuff so I don't know if this actually helps or not. I just don't want to spend almost $200 to make my lights work.
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Old 02-22-2019, 01:44 PM
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Funny timing, because I noticed something this morning that may relate to your investigation.
I also have a delay on the lights going out when you open either door. 15 seconds or so before the lights go out. (As an aside, the Odometer also has a delay after you shut off car.)
Anyway, I was getting something out of the hatch and I noticed that when I opened the hatch all of the interior lights illuminated.
BUT when I closed the hatch they all went out....no delay! I went and opened and closed the passenger door, and the delay still worked.
Thus, on my car opening the hatch turned on all the lights, but closing it just shut them off without delay.
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Old 02-22-2019, 03:20 PM
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Thanks, Jason89s4 ! Good to have that confirmation. I think I've stumped all the electronics experts
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Old 02-22-2019, 03:55 PM
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To follow up with my previous post, when I came home for lunch I went and double-checked and there is more to it...in a weird Porsche-engineering kind of way.

So, like I said before, if you open the hatch all of the other lights come on as well, and if you root around in the back for 30 seconds or more, when you close the hatch all the lights go out without delay.
BUT I just noticed that if you open the hatch, all the lights come on, but then you close the hatch quickly (say within 10 seconds of opening), all the lights go out AFTER a delay!
I tried this a few times and verified. Open and close hatch quickly, the delay works. Leave hatch open for a while, when you close it there is no delay.
So, somehow the relays are set up such that the rear hatch does use the delay circuit for all interior lights if you open and close it, UNLESS you have it open for too long and then close it it doesn't use the delay.
I haven't quite wrapped my head around why they would design it that way.

And a final thought.....what I just described is performed by just using the key to open the hatch, NOT the remote by the doors. If you were to open the door to pull the remote to open the hatch, now you've just thrown another variable into the mix, in that you opened the door! I'm not sure what the effect on the delay circuit would be if you first open the door to pop the hatch, because now you've started the process with the door. I will let someone else go through all of those variables for now. Have to get back to work.
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Old 02-22-2019, 04:08 PM
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Thanks, Jason89s4 . I think it is proof there is alot of logic in the relay and probably why it is climbing up near $200. I am hoping someone with a few more electrons firing than me approves of the jumpering or the alternate relay (with no more delay logic). From there, it MIGHT be possible to retrofit, via jumpers between pins an alternative Lighting Delay relay but for right now, I'll be happy with lights which come on AND shut off with the door or hatch opening.
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Old 02-22-2019, 04:24 PM
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What you proposed with the relay should work (w/ no delay). Using the switches direct actually overloads the door pin switches (since there is ~60W of interior lighting = ~ 5A)

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Old 02-22-2019, 04:31 PM
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Thank you, Alan . I would assume this might also pave the way for using an alternative delay timer. Of course with the understanding behaviors might differ and it would NOT appear stock in its implementation.
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Old 02-22-2019, 05:17 PM
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Yes - the connections are quite simple - pin compatibility is not assured for any other delay relay implementation of course. If you are willing to do adaptations for the connections I'm sure there are many alternative interior light controllers. Note however that the 928 has a high interior light wattage (~6 x 10W on later cars) relative to most cars (unless all/most lights are converted to LED's).

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Old 02-22-2019, 08:46 PM
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The instant relay works off both the rear hatch and the doors now. Unfortunately, the light in the rear hatch now only works when switched ON and not on AUTO.

I do plan on putting in VW lights and LEDs. I'm happy for now using a regular relay and the wiring scheme posted above. I would like to figure out the hatch but I'll wait until the VW lights arrive.

At least there is AN alternative if you don't want to spend mega-bucks on an interior delay relay from Porsche.
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