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Courtesy Light Delay Snag


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#1 MikeSh

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Posted 16 March 2012 - 07:07 PM

I fitted a delay off unit for my interior light at the same time as I put a switch on the passenger side. It seemed fine but (yes, there's always a but) it triggers the alarm beeper when the car is put in gear before the light goes out. This probably only applies to the MMT version as it's the sort of safety thing they do with automatics.
I thought I could fix this with a bit of repositioning and a diode, which I tried today - BUT (again) that changes the behaviour of the unit so the light only stays on for about 1 second instead of 15. Grr!
So for now I've taken it out while I ponder the situation.

Anyone else had this problem and solved it?
Anyone fitted a unit to an MMT and not had the problem? In which case what unit did you use?

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#2 MikeSh

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Posted 20 March 2012 - 01:17 AM

Well, I have plans to sort this and also improve the system as well, but this will need an ignition feed as well.
Rather than running a feed up to the interior light I'm thinking to fit the unit around the right hand end of the dash where I can probably find an ignition wire.
Does anyone know where the courtesy light loom runs from the bottom of the roof pillar?
Or maybe better, where junction block 4D is? This is shown on the wiring diagram but I don't have a location document like I have for the Yaris.

#3 rajivrattna

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Posted 20 March 2012 - 06:12 AM

I weas thinking of fixing a light delay in my wife's Aygo with MMT box but now I think I will avoid it since it is going to confuse her with the beeps.

MikeSh, reading your post again, I get the feeling that you partially solved the problem with a diode. Perhaps putting the diode at a different location might have solved it better? Where did you put the diode? Which wire and position? May be a diagram would help.

#4 rajivrattna

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Posted 20 March 2012 - 07:02 AM

OK Mike Sh I have been looking into this and found an article where BMW E28 (very old car!) had a feature whereby the delay was only activated at the drivers door switch and not to any other door. What would happen if you attached the delay to the wire going to the driver's door switch with a diode in position? Just a thought. I'll attach the article ref. He has done the opposite of what you are trying to do!

http://home.insightb...enyon/delay.htm

#5 MikeSh

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Posted 20 March 2012 - 10:45 PM

The problem with the diode solution is that the volt drop on the diode effectively wipes the delay time out on the unit I have. (It prevents the + side of the delay going all the way to ground when the door switch makes and the capacitor inside the unit doesn't fully discharge which ... blah, blah to do with transistors and stuff :) )

I have a fix for it using a 12V relay instead, but decided while I'm at it to add a function to kill the delay when the ignition is on, hence my second question.

A different delay unit (like one with a timer IC) could probably handle the diode OK, but I can't be bothered to go that way (they are generally self build jobs) as I already have a relay to hand.

When (if) I have it fixed I'll try and post a diagram.

#6 Jan van de Wouw

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Posted 22 March 2012 - 06:37 PM

Where did you mount the deley? at the switch, or at the light?
If the latter, a diode may work, the former it will not help your situation.

#7 MikeSh

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Posted 22 March 2012 - 10:49 PM

Where did you mount the deley? at the switch, or at the light?
If the latter, a diode may work, the former it will not help your situation.

At the light as you say - the diode has to be between the light and the tap-off to the MMT alarm and you can't do this at the switch. The problem with the diode solution and the particular (but very common) delay unit I have is that the 0.7V drop on the diode screws up the operation of the delay.

Although I'm pretty sure my relay solution would work, I've iced the project for now. While playing with the unit on my bench I realised that if the door is open for a long time the delay time gets longer - out to about 50 secs in extremis. As I couldn't get my ignition connection mod to work nicely I've decide to wait and maybe get or make a better delay unit.
If anyone wants a diagram of the relay solution post up and I'll try and put a diagram together.

#8 rajivrattna

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Posted 08 April 2012 - 07:01 AM

Where did you mount the deley? at the switch, or at the light?
If the latter, a diode may work, the former it will not help your situation.


I don't think the diode is going to work because all the door switches and the delay unit at the door are all going to be parallel connections and the current is flowing in the same direction. The only way out is to,
1. Use a separate light unit activated by the other non driver doors and leave the dome light with delay unit connected to the driver's door.
2. Use an expensive time delay relay unit with four connections (ignition wire needed)
3. Attach a cut off relay between the delay unit and the live wire (red) to the dome light. The other two points attached to the trigger, i.e. ignition wire and the ground. This is more like solution 2 but home made.

Unluckily we have two posts dealing on similar subject (yes, I am to be blamed for this partly). Can't we combine them admin!
Here is the other similar thread.
http://www.toyotaown...ic=109454&st=15

#9 MikeSh

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Posted 08 April 2012 - 10:38 PM

This is a diagram of a fix for the delay unit triggering the MMT 'in gear' alarm:

Posted Image

Note that I have not built or tested this, but it's pretty simple.

Basically the relay coil replaces the lamp in the car circuitry (the switches and MMT system) and the relay contact replaces the door switch(es) in the lamp circuit. The delay unit is then wired across the relay contact where it holds the light on but has no effect on the actual door switches and MMT alarm. (Wire colours for door switch wires only added.)

#10 rajivrattna

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Posted 09 April 2012 - 08:07 AM

MikeSAh,
Thank you for posting your suggestion/diagram.
Seems quite elegant (if it works) because you have done away with the ignition wire and are using the delay timer in a different circuit than the MMT alert, thus isolating it. You have also used the door switch as a positive trigger on the relay to connect the bulb to the earth and charge the capacitor in the delay unit at the same time. As the door is closed, the relay cuts off the earth connection to the bulb killing it, but the charged capacitor continues to provide the current to light the bulb for 10-15 seconds and since the MMT alert circuit is isolated from this circuit and that it has no earth connection (because the door is shut ), there is no current flowing in to the MMT alert and that means no sound.

One big caveat is, the position of the MMT alert unit. If it is connected differently from the factory, than what your diagram shows than we are in trouble. Who is going to be brave and try it first!

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