96 maxima dome light fail after mod.

Hello

I made a modification to my interior lighting system of my 1996 Nissan Maxima. The lighting is controlled by the BCM (Body Control Module?). I wanted my map light to turn on and off with dome light when the door was opened. The Map light is controlled by switch (+) lead to the light. In order to make my modification I changed the map light so that it would be switch by ground. I Then connected the LOAD side of the Map light switch to the light and I also connected it to ground turn-on side of the Dome light. I used a DIODE to block from being sent from the Map light when the map light button was turned on. This worked great for about 24 hours and then the next day neither will turn on when the door is open.

I did test the circuit at the spice point of the two lights. When I apply grounded to that junction both lights do come on. To make my connection I did use one of those stupid "Vampire like" piercing connectors. I haven't had time to check to see if that connection had failed on the input side from the BCM, but that is something that I suspect.

My question is: does anyone know if connecting another load to a BCM output can damage the BCM?

Thank You
Brad

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werd

I think you should easily be able to get away with adding another light bulb or two to the BCM, that should be ok.

Have you checked the fuse?

Can you turn on the overhead domelight manually?

Does the door-ajar indicator in the dash still work?

Chris Luongo wrote:

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I think you should easily be able to get away with adding another light bulb or two to the BCM, that should be ok.

Have you checked the fuse?
I did check all the fuses involved (these cars have SO Many Circuits)

Can you turn on the overhead domelight manually?

<Both the dome light and the map light work when turned on manually and both lights work when I apply ground to the "vampire-Like" connector

Does the door-ajar indicator in the dash still work?

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<Yes This indicator works, the car also has the courtesy lights on the two front doors and both of them come up when the doors open. I am going to go out right now and try to trace down the problem again. Thanks for the info

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werd

Ok, I was able to do some testing. I took apart the location of my splice (Top of left hand door pillar) The RED / White wire is the wire that comes from the BCM to the Dome Light. Using my meter I hooked up the positive lead to a constant 12v source and then with the door open I check for ground on this wire. There was no ground present. I also checked for continuity to ground on this wire, and there was none. I just don't see how the BCM could just stop working? No other features or outputs have stopped working, and if I apply ground to the other side of the wire feeding the dome light, it comes on. Anyone have any ideas?

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werd

I was able to verify that the BCM does not put out ground when the doors are open at least not at the point where I spliced it.
I have two questions:

#1. Where is the BCM located? I would like to see if I can that output at the BCM itself. Is that possible? Perhaps its a bad connection between the BCM at the splice point.

#2. Does each BCM Ground output have its own body ground? The reason I ask this is because I am wondering if the ground for the output could have come loose. It deosn't make sense why only that output would not work, but everything else in the BCM seems to be working correctly.

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werd

The BCM is most likely mounted in the driver kick panel.  It does not have seperate ground inputs, they are all common.

The BCM switches both the + and the - of the dome light, but it sounds like you've narrowed it down to the (-) side. 

It is possible, although unlikely, that the added load damaged the BCM.  Typically, BCMs are current limited so if you exceed the current limit by placing more bulbs the bulbs just won't get full power.  One thing you didn't mention, though, is what kind of bulbs you are using.  If you replaced the stock bulbs with some higher wattage bulbs, and then increased the load on the BCM by adding more bulbs it is possible that you damaged the output.

You say you can get the lights to come on by grounding the (-) wire.  You may want to grab a current meter and see how much current it takes to turn on the entire load.  You can then compare that value to the value of the stock bulb(s) and see where you are.  If your new setup requres more then 2x the current of the OEM bulb I would be concerned.

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Kevin Pierson

Kevin

Thanks for your reply. All Bulbs are factory bulbs. The only bulb that I added to the circuit is the map light. I don't that bulb draws much more if any current than the dome light. When I get an opportunity I will test the current load on the circuit. I am looking at my factory Nissan Electrical service manual, and it shows the dome light being power directly from the fuse, not through the BCM.

On my car, the drivers kick panel has a piece of foam rubber backed foil, cover the hole where the BCM is located?

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werd

Update:

The BCM in a 96 Maxima is located in the center console underneath the radio behind the ashtray. You have to remove three 10mm nuts to get the BCM out to look at the connectors which face the front of the car.

I wasn't able to fix my problem like I wanted to. There are two wires on the BCM that RED with a White Stripe. When metered both of those wires, they did the following functions. The first wire appears to be a constant Grounded output. The other wire did sort of act like the dome light wire but for some reason that output did not stay on after the doors were closed.

I cannot figure out why connection was lost (if this second wire is truly what connected to the dome light).

I ended up running a new wire from the top of the drivers door pillar to the BCM. I connected this wire to the wire for the ignition courtesy light. This light is connected to the BCM with a Brown Wire with a Pink stripe. (I think)

I wonder if anyone has a pinout of the Body Control Module? I have an almost complete Nissan Electrical Service manual from Nissanhelp.com.
I cannot find anywhere in this manaul that specifically details the BCM.

Thanks for you help.

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werd