Author Topic: dome lamp  (Read 2357 times)

Offline Harmon

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dome lamp
« on: June 24, 2019, 08:47:37 PM »
86  Chevrolet C10

I put a bulb in the inside dome lamp today.  There has not been one for 10 years since I had truck.  When I put it in, it immediately lit up with the doors closed.

I checked the door jamp switches as far as taking them out and seeing if they were plugged in.  They were.

There is a slight dimming of the dome lamp if I close the doors compared to one being open.

Why would my dome lamp always be on if the doors are closed?

Offline LongBox85

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Re: dome lamp
« Reply #1 on: June 24, 2019, 10:15:02 PM »
Is your light switch (pull type on dash) twisted? mine comes on when it is turned all the way counterclockwise.
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Offline 75gmck25

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Re: dome lamp
« Reply #2 on: June 25, 2019, 05:25:48 AM »
That light always has power, and is grounded by the door switches or by turning the headlight knob in the dash full to the left.   However, its possible that wire insulation is worn somewhere and its finding another path to ground. 

The dome light harness has an orange wire for power and white for ground.  It runs from the light down the driver's side corner of the cab and then under the kick plate and up to the dash. It takes a lot of wear and is subject to water leaks under the door kick plate, so that is the most likely grounding point.

Bruce

Offline Harmon

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Re: dome lamp
« Reply #3 on: June 25, 2019, 10:15:09 AM »
Thanks, I will chase that wire down and see if I see anything.

Offline Harmon

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Re: dome lamp
« Reply #4 on: June 28, 2019, 11:10:19 AM »
Driver door jamb wires fell off as I was pulling it out of the cab.  Any ideas to fish those out?

Offline Harmon

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Re: dome lamp
« Reply #5 on: June 28, 2019, 11:28:30 AM »
Got them out...used a coat hanger...didnt think that would work but it did!

Still have same issue with dome lamp always being on, and cargo lamp is on as well.

Wires look good at door sill plate to under dash, and they look good to the connector at B pillar.

Online bd

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Re: dome lamp
« Reply #6 on: June 28, 2019, 11:35:29 AM »
Why would my dome lamp always be on if the doors are closed?


Is your light switch (pull type on dash) twisted? mine comes on when it is turned all the way counterclockwise.

This ^^^^


Make sure the headlamp switch knob IS NOT rotated all the way CCW.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Harmon

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Re: dome lamp
« Reply #7 on: June 28, 2019, 12:28:11 PM »
I replaced the head lamp switch.  I am sure that it is not twisted therefore turning on dome lamp.
The light dims as both doors are shut.  Does not totally go off. 


Where does the orange and white wires go under the dash.  I see them go behind the fuse junction block.  I assume they go to the driver door jamb switch.  Where does the hot wire go?

Passenger side door jamb switch only has a white wire going to it.  Ive read that is normal.  I followed the white door jamb switch wire to the other under dash courtesy light.  That light has no bulb in it.  Does it have to have one to make this all work correctly? 

Im kind of at a loss.  I can sit in truck with doors closed and wiggle wires and there isnt any dimming or flickering of lights either.

Online bd

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Re: dome lamp
« Reply #8 on: June 28, 2019, 02:26:16 PM »
Have you looked at the 1986 Wiring Manual?  You may need to open it in Acrobat Reader for it to display correctly.

The dome/courtesy lamp circuit is different from most of the other circuits in your truck in that the circuit is switched on the "ground side" of the lamps.  That is, the dome/courtesy lamps receive fused B+ power all of the time (via the orange wires) and then illuminate only when the lamps are grounded through the door jamb and/or headlamp switches via the white wires coming from the lamps.  For the lamps to illuminate, one of the white wires is grounded somewhere between the lamps and one of the switches OR one of the switches is completing the white wire circuit to ground. 

To determine whether the issue is in the wiring or one of the switches, remove the door jamb switches and disconnect the white wires letting them hang free so that they do not contact the cabin sheet metal.  Unplug the instrument panel (I/P) harness from the headlamp switch, but do not remove the headlamp switch from the dash.  If the interior lamps continue to illuminate, one or more of the white wires is grounded - somewhere.  Unplug the inline two-wire harness connector at the base of the left B pillar and jumper orange-to-orange.  If the lamp goes out, begin tracing the white wire forward from the left B pillar connector, under the driver side sill plate and under the dash to the headlamp switch and both door switches.  It's common for the white wire to be pinched under the sill plate or perforated by a sill plate screw.  Look carefully.  If the lamp remains illuminated, the white wire is grounded between the inline connector and the dome lamp.

If through all of the foregoing the dome lamp remains extinguished, reinstall the I/P harness to the headlamp switch.  If the dome lamp illuminates, the headlamp switch is the culprit - try rotating the knob CW.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Harmon

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Re: dome lamp
« Reply #9 on: June 28, 2019, 06:18:15 PM »
Ok, it is now working properly...

BD I did as you stated....found the issue to be between the b pillar to the dome lamp.  Still not exactly sure where.  The light stopped staying on all the time once I took the base off the cargo lamp.  Perhaps something there was doing something? Not sure, but after I jumper wired the orange wire at the bottom of the B pillar, it all started working properly... So its fixed, but not exactly sure what the culprit was.

Thanks for the info!

Online bd

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Re: dome lamp
« Reply #10 on: June 28, 2019, 07:28:17 PM »
The wire insulation may have been perforated by a screw or chafed across a sharp sheet metal edge.  Simply moving the wires around while checking them may have dislodged the white wire from grounding out - at least for the interim.  If the problem recurs you'll know where to pick up your diagnosis and concentrate your efforts.  Take the time to learn to use the wiring manual.  It's your friend.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Harmon

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Re: dome lamp
« Reply #11 on: June 28, 2019, 09:00:41 PM »
Sometimes they help, but I am color blind.  I have to see where the wire is in relation to being on the vehicle in order for it to give me a chance.  Then send people pictures to ask what color is this wire.  Thats how I found out the water temp sensor wire is green!

Online bd

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Re: dome lamp
« Reply #12 on: June 28, 2019, 09:54:12 PM »
I suppose that infinite shades of gray must present a modest challenge in a full spectrum world.  Certainly not insurmountable, but sometimes pesky.  Like a missing subwoofer.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)