interior light dimming circuit

[Chris Hawes]

I have seen other cars with this problem, so it can't be that unusual. The interior lights (one near the rear view mirror and the other mounted above the middle of the rear parcel shelf) have three tiltable settings:- OFF/ON WHEN DOORS OPEN/ALWAYS ON/

The 'OFF' or continous 'ON' work fine. The problem is the 'ON WHEN DOORS OPEN' setting on my car they stay off. The white relay:-



when plugged it does nothing. I guess it could be faulty, is there an easy test?

What else could cause this?

Cheers

[Rich H]

The white module adds in the delay, so when you remove it you will simply have no delay on your interior lights.

If you have no interior lights when either door is open, it will probably be a faulty diode (repairable) or your interior lights are wired up incorrectly.

I'll post a piccy of the correct wiring.....

[Chris Hawes]

You mean like this? (borrowed from www.specialtauto.com)

[Rich H]

Yeh, thats it

If yours is wired OK then it's quite probably a loose connection, or a diode.

There are three off them to the right of the drivers footwell next to the centre console.

Testing the wiring is easier to do than explain - have you got a wiring diagram?

[stunned_monkey]

Does your door ajar light work on the dash?
Are your door lights plugged in?
I know you've been tinkering around under your dash - the diodes are there for the interior light circuit as Rich says.... I've seen a couple of failed ones.

[Chris Hawes]

My door ajar circuits work, i.e. you open a/both door(s) and the red ajar light comes on. The wiring to at least one of the interior lights is spot on (i don't want to disturb the light near the rear-view mirror unless I have too).

Th diodes could be it then Martin. The centre console is still out at the moment. What do they look like so that I can check them?

Cheers

[Chris Hawes]

The diodes were okay. After cleaning up the contacts on the rear luggage light I found that it worked as it should, well kind of. Operation I would describe as 'twitchy'.

The front light would light up on the 'permanently on' setting but do nothing on the door activation setting.

I decided to purchase a pair of replacements from DMCL. Having received them the top of the casing is much taller than the OEM version which does not affect fitting at the front near the mirror but the second unit for fitting below the rear firewall required a little 'modification' to allow it to sit that bit higher so that it could mount into the panel properly.

The 'dark grey' looks a lot better than the overly glossed black of the original. Operation feels more 'expensive' as the dome gently tilts quietly between the three settings. It is quite possible that the dirty/poor contacts that grinded between positions would have been to blame on the 25 year old OEM item. Having just fitted them I am delighted with the results and recommend them over the OEM.

For the first time in my ownership, when I open/close the door I now have two lights that come on/go out accordingly

I have now refitted the white 'delay' relay that came with the car and find that it dims the lights around 10% when you close the door and then around 1-2 seconds later it turns the lights out.

I had gotten it into my head that the delay would be longer and I would prefer a slow fade to off (I have stuck with original festoon bulbs). Could this be easily done with an aftermarket relay? :?:

[stunned_monkey]

The "switch" on the orignal sis not a switch. It's a copper ring being wedged between two bits of metal. It's not "designed" and hardly ever works after 25 years. They're badly made, simply.

They are a tight fit on the rear but I've never had a problem fitting any myself, nor any other complaints so far. Are you sure there was nothing above it ?

The dark grey vs black thing is just how they're made, and nobody who wasn't pre-briefed has ever noticed :-)

We can also get them in brown and I've got a chrome one, but they're not available any more!

[Rich H]

Quote:I had gotten it into my head that the delay would be longer and I would prefer a slow fade to off (I have stuck with original festoon bulbs). Could this be easily done with an aftermarket relay?

The white module is not a 'relay' as such, it is the most badly designed, over complex, bodge of a 'circuit' I've ever seen. I took me and a friend with some heavy duty simulation software an entire day to even attempt to understand what the designer was attempting to do - in the end we gave up. But I digress...

I have redesigned the module so that it works on either bulbs or LEDs, but I was niggled by the slight drop in brightness when the doors where initially closed and shelved the project for further development. Since this appears to be what the originals do anyway, perhaps it may be worth resurecting again?...

[Chris Hawes]

I noticed that slight drop in brightness too (10%) on mine. I like to think that it is its feeble attempt at dimming and then gives up and just shuts the lights out. If you create, I will buy

[Rich H]

No fading intended on the original, the 10% reduction is just a quirk

You'll also notice, that if you open the door and then close it almost imediately you'll get the delay, but leave it open for 5 minutes and then close it, and the delay has gone! Even with all the ridiculous circuitry in there it still dosen't work properly!
Good old Pektron Derby (also responsible for the ill fated Fan Fail Module)........still in business

I can get as long a delay as you like, but sadly it's almost impossible to get a dimming circuit that would plug into the original holder.

[stunned_monkey]

How about buying "new" green ones and ripping the guts out ? Plenty of room for a PCB in them

pn 108164

[Rich H]

Enclosing the thing isn't a problem, I've already done that.

The the problem with doing a dimming circuit is there aren't the right/enough connections to the module from the wiring loom, without bodging in additional cables...

[Chris Hawes]

surely the additional cables can be 'carefully' integrated into the wiring loom so that bodging is not necessary?

[stunned_monkey]

"carefully integrating" is another way of saying "bodging" if you want a "plug and play" solution