Door courtesy light switch electrical issue

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spurcap

spurcap

Joined
Nov 21, 2012
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Location
Vancouver, BC
So my truck's (1991 HDJ81) rear courtesy light switches had not functioned for the longest time and I figured I would try and fix it today.

I was fairly confident it was the switches given not only did the light not come on but the dash light for door open didn't come on either when either of the rear doors were open.

I started on the back left side and took the sensor off. I got out my volt meter and tried connecting the wire from the sensor to the ground -- 12V. That made me figure that the switch functions to ground out this wire to make the light go on, therefore I got a piece of wire and connected it to the ground and the dome light came on. Therefore I knew it was the switch. I sprayed it with electrical cleaner and moved it around and cleaned the ground and put it all back together. Success!

Now going onto the other door I went through the same process ... checked with volt meter and got 12V. But when I connected the 12V source to the ground - no light? I really can't figure out how this makes any sense ... And reading the electrical book didn't help ...


Any ideas?
 
robertk61 said:
yeah mine don't work either, would like to know what fixes it?
Click to expand...

Did you check if the cable in yours is getting 12V? If so, does grounding it make the light go on?

If yes - I would say try cleaning the switch itself and if that doesn't work, just replace it.
 
Screenshots of the wiring diagram for a '96. Not sure if it's the same for a '91. I'm not smart enough to know what's going on in this diagram but you can see the relay in the upper right corner (blue box)

11192024835_a40fe7c8ff_o.jpg
 
spurcap said:
Now going onto the other door I went through the same process ... checked with volt meter and got 12V. But when I connected the 12V source to the ground - no light? I really can't figure out how this makes any sense ... And reading the electrical book didn't help ...QUOTE]

This makes sense because there are also lights in the doors, plus the one in the dash.
Did you notice if any of those came on when you did this test?
Click to expand...
 
There is definately a relay but given the other three doors work and there is only wire going to all of them (they look to be connected in parallell?) I don't really see how the relay could be the problem in my case....

It seems that if the circuit to any of the doors grounds out then the relay triggers the lights to go on. Given I have power to the broken door, I can't seem to make sense of it.

I used the same bolt as a ground to do my voltmeter test (got 12V) so I know the ground isn't the problem. I can't seem to see how grounding out this wire won't trip the light if its getting power ....
 
So it sounds like the Rear Right switch is working, but isn't turning on the light? Have you checked the light bulb socket itself to see if it's getting power? Maybe a damaged wire or connector somewhere along the line?

If you look at the diagram I posted you can see the Right Rear switch (D19) is on a separate line from the others, not sure if that makes a difference.
 
Not sure about the '91, but if you you look at the diagram above there are 3 other paths to +12V leading to that door switch. (through the other lamps)
 
Last edited:
landcrshr said:
This makes sense because there are also lights in the doors, plus the one in the dash.
Did you notice if any of those came on when you did this test?
Click to expand...

I will try again tonight as I didn't check if the dash light came on or not; however, on the left side door when grounding the wire that goes to the switch the dome light comes on while the right hand side it doesn't so something doesn't make sense there.

I don't know what lights in the doors you are talking about but perhaps this was something on North American 80s while my JDM one doesn't have it?
 
Hmm, no door courtesy lights? OK.

Well, I suspect the connection is bad between the right door and the left door, but you still have a good connection to the open-door warning light and that's why you read the 12V at the switch.
 
jcardona1 said:
So it sounds like the Rear Right switch is working, but isn't turning on the light? Have you checked the light bulb socket itself to see if it's getting power? Maybe a damaged wire or connector somewhere along the line?

If you look at the diagram I posted you can see the Right Rear switch (D19) is on a separate line from the others, not sure if that makes a difference.
Click to expand...

The thing that doesn't make sense to me is that the light is on a relay that turns the bulb on if the sensor circuit LOOSES power ... the switches are sent a wire (or 3 as you note) that give a 12V supply and if those wires are grounded (what the switch does when the door opens) then the light comes on. Given, power is going there, I can't figure out why grounding it is doing nothing ....

To clarify, the light does come on when any of the other three doors are opened so I am fairly confident it isn't the socket itself.
 
landcrshr said:
Hmm, no door courtesy lights? OK.

Well, I suspect the connection is bad between the right door and the left door, but you still have a good connection to the open-door warning light and that's why you read the 12V at the switch.
Click to expand...

So you're thinking the wire that controls the courtesy light is not properly connected to the switch and therefore is not getting grounded when the switch's wire is grounded? That seems to make sense.

I think my next step when I get out of work is to see if I can get the door open indicator on the dash to turn on by opening the door/grounding the switch wire.
 
Right, also confirm that the open-door light works properly for all of the doors. If there's a bad connection, it may not come on for the other rear door. (even though the domelight works on that side)
 
Can you post up the "interior light" section of your EWD?
 
I don't have a factory alarm but I do have a s***ty aftermarket one ... (not sure if from Japan or after the PO got it to NA)

Perhaps whoever installed the alarm just disconnected the switch from the rear right door (which would make sense as the alarm is installed under the dash on the drivers' side) in order to get a signal to the alarm... Or they tapped into the switch and ran a cable back to the circuit for the courtesy but that got disconnected.

I think this is a good thing to check out. Thanks for the idea.
 
Given I am also having issues with my front corner parking lights, I think this all comes back to the s***ty aftermarket alarm that the truck has had since I purchased it ....

Both would be items that the alarm would use (the courtesy light circuit would be used to sense when a door was opened, and the front parking lights are used to blink when the alarm goes on).

I tihnk this may be the place to start exploring.
 
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