Trouble with interior lights
11-17-2018, 03:17 PM
#1
Trouble with interior lights
I need some help dealing with what should be a simple electrical issue!
I think my problems all started over a year ago when I tried installing LED interior lights that a guy here on the org was selling. None of the LEDs worked, and when I went to reinstall the stock bulbs, I had trouble getting them to work again. Since that time, the door light on my DS door hasn't worked, no matter how many new bulbs I try. Same thing with one of my front map lights. The main interior light has been weak and intermittent since I tried an LED in its place too.
Well today I decided I would dig into the problem and see if I could fix it. I popped off the cover for my dead DS door light and checked for continuity with my multimeter, and it had continuity. However when I checked to see if it had power, I got something like 0.03V. I had my MM set to DC10A. Pushing and releasing the door plunger didn't change the reading. I then went over to my working PS door light. I pressed the plunger down and removed the bulb. It had continuity, but when I released the plunger, it didn't have any power going to it. I then pressed the plunger back down and plugged the bulb back in. It no longer works, and it's not burnt out! I then went to check the front map lights. The one on the DS hasn't worked in a while, but the PS one has. I checked for continuity with the PS bulb lit up. The DS had continuity, but when I checked the lit up PS bulb, it went out and never came back on! The PS has continuity. It's almost like I'm blowing out fuses for the individual lights, but I know those don't exist. I went around and checked all my fuses with my MM and all have continuity. How in the world are the lights dying just by me removing them or touching them with my MM? Why are they not getting power?
Also, I re-tried the procedure to have the body module check for error codes associated with the door locks, since my door locks have a mind of their own, and I often have to unlock the car (with my alarm fob) five times before all the doors unlock. When I did this test a year ago, it said the PS front door lock actuator was bad. Today, with most of the interior lights burnt out, I was unable to get the car into diagnostic mode. I wonder if the diagnostic mode can only be accessed if all/most of the interior lights are working? IIRC it uses the interior lights to tell you what the code is by blinking.
My electrical troubleshooting skills are pretty weak, but I'm trying to learn. Does anyone have any ideas as to what I've done to my poor car?
I think my problems all started over a year ago when I tried installing LED interior lights that a guy here on the org was selling. None of the LEDs worked, and when I went to reinstall the stock bulbs, I had trouble getting them to work again. Since that time, the door light on my DS door hasn't worked, no matter how many new bulbs I try. Same thing with one of my front map lights. The main interior light has been weak and intermittent since I tried an LED in its place too.
Well today I decided I would dig into the problem and see if I could fix it. I popped off the cover for my dead DS door light and checked for continuity with my multimeter, and it had continuity. However when I checked to see if it had power, I got something like 0.03V. I had my MM set to DC10A. Pushing and releasing the door plunger didn't change the reading. I then went over to my working PS door light. I pressed the plunger down and removed the bulb. It had continuity, but when I released the plunger, it didn't have any power going to it. I then pressed the plunger back down and plugged the bulb back in. It no longer works, and it's not burnt out! I then went to check the front map lights. The one on the DS hasn't worked in a while, but the PS one has. I checked for continuity with the PS bulb lit up. The DS had continuity, but when I checked the lit up PS bulb, it went out and never came back on! The PS has continuity. It's almost like I'm blowing out fuses for the individual lights, but I know those don't exist. I went around and checked all my fuses with my MM and all have continuity. How in the world are the lights dying just by me removing them or touching them with my MM? Why are they not getting power?
Also, I re-tried the procedure to have the body module check for error codes associated with the door locks, since my door locks have a mind of their own, and I often have to unlock the car (with my alarm fob) five times before all the doors unlock. When I did this test a year ago, it said the PS front door lock actuator was bad. Today, with most of the interior lights burnt out, I was unable to get the car into diagnostic mode. I wonder if the diagnostic mode can only be accessed if all/most of the interior lights are working? IIRC it uses the interior lights to tell you what the code is by blinking.
My electrical troubleshooting skills are pretty weak, but I'm trying to learn. Does anyone have any ideas as to what I've done to my poor car?
11-18-2018, 02:15 AM
#3
Senior Member
Join Date: Oct 2012
Location: Portland, Oregon
Posts: 2,979
Sometimes it's easier to understand electrical concepts by visualizing water flowing through hoses.
Voltage is like psi. amps is like volume.
you measured voltage. It indicates that voltage is there, but voltage alone won't do the job.
A bulb lights if the voltage (pressure) is sufficient, but it also needs amps (volume).
You are getting voltage, but very little amps, or current flow.
You probably have a bad contact, or corrosion somewhere. So the volt meter reads properly.
Yet there is not enough amps to light the bulb.
This is like trying to fill a swimming pool through a soda straw. The straw has little volume, and the 12v means low pressure. You would indeed get water.
But not enough water.
Voltage is like psi. amps is like volume.
you measured voltage. It indicates that voltage is there, but voltage alone won't do the job.
A bulb lights if the voltage (pressure) is sufficient, but it also needs amps (volume).
You are getting voltage, but very little amps, or current flow.
You probably have a bad contact, or corrosion somewhere. So the volt meter reads properly.
Yet there is not enough amps to light the bulb.
This is like trying to fill a swimming pool through a soda straw. The straw has little volume, and the 12v means low pressure. You would indeed get water.
But not enough water.
11-18-2018, 08:58 AM
#4
Welp, I'm an idiot. I went through my electrical books and some youtube videos this morning and realized I made a terrible mistake yesterday. When I was testing for voltage, I had the red lead plugged into the 10A hole on the MM instead of the voltage hole, and I'm pretty sure I made the problem worse. The reason I had it in there instead of the V hole was because I was previously testing for a parasitic drain, which I believe is tested using the amp setting. The only thing is I'm not sure how or where I made the problem worse, since I can't find a blown fuse anywhere. Is there a module that controls all the interior lights that I could have blown up?
11-18-2018, 10:36 AM
#5
Senior Member
Join Date: Oct 2012
Location: Portland, Oregon
Posts: 2,979
I dont believe that the small batteries in the vom would have suffucent amperage (current) to make your issues worse.
I still believe that you have a bad/corroded contact somewhere which chokes off amperage
I still believe that you have a bad/corroded contact somewhere which chokes off amperage
11-18-2018, 01:48 PM
#6
To start with, all the light bulbs in the maxima are connected to 12 volts. To turn the light on, the switch connects it to ground.
Changing the light bulbs in the door panel (these are called step lights) is a delicate process. It is very easy to short the socket if you are trying to "dig" the bulb out with a screwdriver. It you did this on the driver's door, you're screwed. Sorry for the bluntness. You shorted out the master power window switch in the driver's door and you will have to replace it.
The map light situation is a little more interesting. Because they are difficult to take out, coupled with the fact that the socket is wired in reverse of all other light sockets in the world, you can easily blow the fuse if you use a screwdriver. If you do, you replace the fuse and life is good again. Other than physical damage to the light socket, the switch or the wire, I don't know why one light would not work. The electrical circuit is pretty basic - battery ---> 7.5 amp fuse # 26 ---> light holder in roof ---> a Y connection to the light bulbs ---> to the on/off switch ---> to ground. The fuse also powers the lights on the sun visor vanity mirrors as well as the light in the trunk.
As for having the multimeter in the amps mode, that should not cause any problems depending on how you had it connected into the light circuit. It is like a short circuit if you are using the probes as if you are measuring voltage. Then you will blow the fuse for that circuit, just like if you had stuck a screwdriver in the socket.
Changing the light bulbs in the door panel (these are called step lights) is a delicate process. It is very easy to short the socket if you are trying to "dig" the bulb out with a screwdriver. It you did this on the driver's door, you're screwed. Sorry for the bluntness. You shorted out the master power window switch in the driver's door and you will have to replace it.
The map light situation is a little more interesting. Because they are difficult to take out, coupled with the fact that the socket is wired in reverse of all other light sockets in the world, you can easily blow the fuse if you use a screwdriver. If you do, you replace the fuse and life is good again. Other than physical damage to the light socket, the switch or the wire, I don't know why one light would not work. The electrical circuit is pretty basic - battery ---> 7.5 amp fuse # 26 ---> light holder in roof ---> a Y connection to the light bulbs ---> to the on/off switch ---> to ground. The fuse also powers the lights on the sun visor vanity mirrors as well as the light in the trunk.
As for having the multimeter in the amps mode, that should not cause any problems depending on how you had it connected into the light circuit. It is like a short circuit if you are using the probes as if you are measuring voltage. Then you will blow the fuse for that circuit, just like if you had stuck a screwdriver in the socket.
11-18-2018, 04:01 PM
#7
Thanks for posting, that's more or less is what my buddy told me over the phone. I learned my lesson about using the amp hole on the MM! I had it in there because I had just finished testing for a parasitic drain and I didn't think to switch it back to V/ohm. I clearly can't learn electrical stuff from a book, so I guess I'll just have to keep making mistakes until it sinks in! 
As far as I can tell the MM is still working, so I've got that going for me....
I re-did my tests using correct methodology that my friend walked me through over the phone. Thanks Brian, you're the best! Here are the results:
And here's some info about the body control module (BCM) from the FSM:
Brian seems to think I've got a bad ground somewhere related to the PS door light. He recommended I find trace it to the ground and/or the BCM. What I don't understand is how I had three working lights yesterday (out of five) if I have a bad ground. If there are no blown fuses right now, and lights still aren't working in any location, I can't help but think something fried inside the BCM. Brian also wondered if one of the door switches/plungers is going bad and not letting enough current get to the bulbs. We know everything is getting voltage, but we don't know what's going on with the current. Am I understanding this correctly?
The BCM controls my locks, interior lights, and the sleep mode for the car. I've got no interior lights, locks with a mind of their own, and a HUGE parasitic drain. If the BCM is faulty and not going into sleep mode, I believe that could cause a large drain, no? My lack of understanding is pushing me to believe the BCM is the cause of all my problems, but I know it's probably not that simple. Does anyone know what is typically involved with replacing a BCM on a 90s Japanese car? Does it need to be programed to match my car/key?
More to the point, since I'm unable to make sense of wiring diagrams, how can I figure out where the ground is for that PS door light? I'm pretty sure I should start there, but I'm not sure how.
Thanks to everyone who has responded! I'm pretty dumb when it comes to this stuff, but I'm determined to learn!
As far as I can tell the MM is still working, so I've got that going for me....I re-did my tests using correct methodology that my friend walked me through over the phone. Thanks Brian, you're the best! Here are the results:
And here's some info about the body control module (BCM) from the FSM:
Brian seems to think I've got a bad ground somewhere related to the PS door light. He recommended I find trace it to the ground and/or the BCM. What I don't understand is how I had three working lights yesterday (out of five) if I have a bad ground. If there are no blown fuses right now, and lights still aren't working in any location, I can't help but think something fried inside the BCM. Brian also wondered if one of the door switches/plungers is going bad and not letting enough current get to the bulbs. We know everything is getting voltage, but we don't know what's going on with the current. Am I understanding this correctly?
The BCM controls my locks, interior lights, and the sleep mode for the car. I've got no interior lights, locks with a mind of their own, and a HUGE parasitic drain. If the BCM is faulty and not going into sleep mode, I believe that could cause a large drain, no? My lack of understanding is pushing me to believe the BCM is the cause of all my problems, but I know it's probably not that simple. Does anyone know what is typically involved with replacing a BCM on a 90s Japanese car? Does it need to be programed to match my car/key?
More to the point, since I'm unable to make sense of wiring diagrams, how can I figure out where the ground is for that PS door light? I'm pretty sure I should start there, but I'm not sure how.
Thanks to everyone who has responded! I'm pretty dumb when it comes to this stuff, but I'm determined to learn!
11-18-2018, 04:20 PM
#8
To start with, all the light bulbs in the maxima are connected to 12 volts. To turn the light on, the switch connects it to ground.
Changing the light bulbs in the door panel (these are called step lights) is a delicate process. It is very easy to short the socket if you are trying to "dig" the bulb out with a screwdriver. It you did this on the driver's door, you're screwed. Sorry for the bluntness. You shorted out the master power window switch in the driver's door and you will have to replace it.
The map light situation is a little more interesting. Because they are difficult to take out, coupled with the fact that the socket is wired in reverse of all other light sockets in the world, you can easily blow the fuse if you use a screwdriver. If you do, you replace the fuse and life is good again. Other than physical damage to the light socket, the switch or the wire, I don't know why one light would not work. The electrical circuit is pretty basic - battery ---> 7.5 amp fuse # 26 ---> light holder in roof ---> a Y connection to the light bulbs ---> to the on/off switch ---> to ground. The fuse also powers the lights on the sun visor vanity mirrors as well as the light in the trunk.
As for having the multimeter in the amps mode, that should not cause any problems depending on how you had it connected into the light circuit. It is like a short circuit if you are using the probes as if you are measuring voltage. Then you will blow the fuse for that circuit, just like if you had stuck a screwdriver in the socket.
Changing the light bulbs in the door panel (these are called step lights) is a delicate process. It is very easy to short the socket if you are trying to "dig" the bulb out with a screwdriver. It you did this on the driver's door, you're screwed. Sorry for the bluntness. You shorted out the master power window switch in the driver's door and you will have to replace it.
The map light situation is a little more interesting. Because they are difficult to take out, coupled with the fact that the socket is wired in reverse of all other light sockets in the world, you can easily blow the fuse if you use a screwdriver. If you do, you replace the fuse and life is good again. Other than physical damage to the light socket, the switch or the wire, I don't know why one light would not work. The electrical circuit is pretty basic - battery ---> 7.5 amp fuse # 26 ---> light holder in roof ---> a Y connection to the light bulbs ---> to the on/off switch ---> to ground. The fuse also powers the lights on the sun visor vanity mirrors as well as the light in the trunk.
As for having the multimeter in the amps mode, that should not cause any problems depending on how you had it connected into the light circuit. It is like a short circuit if you are using the probes as if you are measuring voltage. Then you will blow the fuse for that circuit, just like if you had stuck a screwdriver in the socket.
I went back for like the 4th time and did find fuse #26 to be blown. Maybe I missed it before since it's up so high in the box? Interestingly enough, I found a 10A fuse in there, even though it's supposed to be 7.5A. Hopefully that extra current that got through didn't mess up whatever that fuse is protecting
I JUST went out and replaced all of the interior bulbs, and I now have map and overhead lights back!!!!!!!!!!!!!!!!!!!!!! But still, no door lights. Back to the drawing board....
11-19-2018, 02:02 PM
#9
Looking at the Excel spreadsheet you posted yesterday, what is the difference between columns B and C? the are both titled "MM grounded to seat bolt".
If you shorted the step lamp socket and damaged the power window switch, this would not affect the windows or door locks. How ever the window switch is designed, the step lamp circuit seems to be independent from the other sections.
The step lamp in the driver's door is controlled by the window switch in the driver's door. The step lamp in the passenger door is controlled by the window switch in the passenger door.
If you remove the step lamp light bulb, you should measure 12 volts from fuse # 26 on one of the contacts. The other contact goes to the power window switch and gets connected to ground when the door is opened. With the light bulb out of the socket, you won't measure any voltage on this pin. If you could measure this pin with the light bulb plugged in, you would find 12 volts when the door is closed and basically zero volts when the door is open. Since you can't put the voltmeter probe on the pin with the light bulb plugged in, you would have to be checking Pin 8 on the backside of the power window switch. Pop the window switch out of the door panel to do this. You want pin 8 of the big connector. Pin 10 is one of the corners and it has a red with yellow stripe wire in it. Pin 6 next to the keyway has a light green with red stripe wire in it. I don't know the color of the wire in pin 8.
Finding the blown fuse is a good thing as it brings things back into the realm of normal problems. If you are unfortunate to have a lot of electrical problems, you will learn that a visual inspection of the fuses does not always reveal a bad fuse. If the fuse looks good, do a continuity test on the fuse.
Using a higher amperage fuse will not cause more amperage to be pushed through a device. An electrical device will never use more electricity than it was designed to use regardless of the fuse size.
The only time a higher amperage fuse becomes an issue is when a short circuit occurs.The wire used to connect the device can carry only so much amperage, based on the gauge (thickness) of the wire. If the fuse is too high an amperage rating, then you could end up with burned up wires when a short happens.
In the case of a 10 amp fuse used in place of a 7.5 amp fuse, I doubt if it would make any difference even if there were to be a short. Good electrical design says to use parts that handle more amperage than what is intended as a safety factor.
I can't be sure, but I'm pretty sure I would have removed the door bulbs (when I did one originally last year) just with my fingers and not a screw driver. If I shorted out the master power window switch, wouldn't that also affect my windows and locks? My windows work fine, and aside from wonky door lock issues, which existed long before any light issues, they generally work as well. All lights work on the DS power window switch as well. But I'm not opposed to picking one up at the junkyard and trying it out.
The step lamp in the driver's door is controlled by the window switch in the driver's door. The step lamp in the passenger door is controlled by the window switch in the passenger door.
If you remove the step lamp light bulb, you should measure 12 volts from fuse # 26 on one of the contacts. The other contact goes to the power window switch and gets connected to ground when the door is opened. With the light bulb out of the socket, you won't measure any voltage on this pin. If you could measure this pin with the light bulb plugged in, you would find 12 volts when the door is closed and basically zero volts when the door is open. Since you can't put the voltmeter probe on the pin with the light bulb plugged in, you would have to be checking Pin 8 on the backside of the power window switch. Pop the window switch out of the door panel to do this. You want pin 8 of the big connector. Pin 10 is one of the corners and it has a red with yellow stripe wire in it. Pin 6 next to the keyway has a light green with red stripe wire in it. I don't know the color of the wire in pin 8.
I went back for like the 4th time and did find fuse #26 to be blown. Maybe I missed it before since it's up so high in the box? Interestingly enough, I found a 10A fuse in there, even though it's supposed to be 7.5A. Hopefully that extra current that got through didn't mess up whatever that fuse is protecting I JUST went out and replaced all of the interior bulbs, and I now have map and overhead lights back!!!!!!!!!!!!!!!!!!!!!! But still, no door lights. Back to the drawing board....
I JUST went out and replaced all of the interior bulbs, and I now have map and overhead lights back!!!!!!!!!!!!!!!!!!!!!! But still, no door lights. Back to the drawing board....Using a higher amperage fuse will not cause more amperage to be pushed through a device. An electrical device will never use more electricity than it was designed to use regardless of the fuse size.
The only time a higher amperage fuse becomes an issue is when a short circuit occurs.The wire used to connect the device can carry only so much amperage, based on the gauge (thickness) of the wire. If the fuse is too high an amperage rating, then you could end up with burned up wires when a short happens.
In the case of a 10 amp fuse used in place of a 7.5 amp fuse, I doubt if it would make any difference even if there were to be a short. Good electrical design says to use parts that handle more amperage than what is intended as a safety factor.
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