1988 K2500 courtesy lights/dome light problems

[evilunclegrimace]

Just to clarify; the dome light should come on when you open the door, the map/reading light should come on with the reostat switch on the dash.

 

[Firewood truck]

Do u have pictures of those wiring schematic? Can u post them.

I found them in this site, they're stickied somewhere.

Just to clarify; the dome light should come on when you open the door, the map/reading light should come on with the reostat switch on the dash.

yes, the electrics are working as they should. The speedo is still dead a lot more then it works, and when it "works" it's still off by about 10mph ( compared to Garmin GPS ). I had the doors apart recently, installing new lock cylinders. The drivers door will lock/unlock from the outside but ONLY if the interior lock stays in the "open/unlocked" position. IF I lock the drivers door from the inside, I can't unlock it with the key. The pass side is almost as flaky- I can lock the door from the inside and unlock it with the key, I just can't lock it with the key regardless if the interior lock is open or closed ( locked). It keeps things interesting.

The newest problem is that the clutch pedal is back to not working very well. I used the truck last Saturday to get some lumber for my deck. While pulling into a gas station, the truck started to jerk/creep forward a bit, then I couldn't pull the trans out of gear until it stalled. I had to pump the pedal a bunch of time to get the clutch to release. The fluid is jet black. I'm baffled because the master, slave and hydro line are all brand new Raybestos parts. The steel line isn't very close to the exhaust pipes, so I'm not sure what's going on.

 

[denverdriveby]

I've got a 1991 k3500 I'm restoring.

Can you guys first clarify which is the dome light and which is the map reading light? I've got two overhead interior lights, one round one with toggle switch (which I assume activates the exterior roof cab lights?) and a rectangular light at rear ceiling of cab by back glass. What is correct name of each light so I can understand schematic?

My issue is the rear ceiling rectangular light stays on even when doors closed and headlight/parklight/dimmer switch in any position. I hate to guess but assume one or both of the door switches are bad, since those are cheap switches, I'll order replacements for sake of reliability but I'd like to troubleshoot with multimeter to verify.

Also, I cannot get the round ceiling light in center of ceiling to work and I'm not sure about the toggle switch on it. It is connected by single wire to the rear rectangular light. Does that round light need to be screwed/grounded to metal ceiling to complete circuit before it lights up and works? It's currently hanging down in preparation to install new headliner.

Lastly, I'm not clear on how to turn on/off all the various lights at the switches: rectangular light back ceiling of cab, overhead round ceiling light of cab, exterior roof cab lights, headlights, parking lights, etc. I don't have an owners manual for truck.

Not knowing the proper names of lights or switches and not knowing normal expected functionality of lights and switches makes troubleshooting tough.

Thank you for great website and wonderful knowledge and experience

Dutch in Colorado

 

[denverdriveby]

Thanks for that info, it helped on the trouble shooting. Have you tested the door jam switches? When they go bad, it can keep the lights from turning on.

The schematics that I got from this site were very helpful. I got power up to the overhead courtesy lights, I'm just not sure if they are supposed to come on when the doors are open. I got the lower courtesy lights working with doors and the dimmer switch, the upper light is odd ( at least to me) I can turn on one side ( map light) or the other, but if both get turned on the big middle bulb lights up. It goes off when I door is opened, so it only works with the door closed and either by the dimmer switch or the little black buttons on each side of the housing.

I'm not 100% what my issues were, once I installed new bulbs in the lower courtesy light sockets and jumped the harness that plugs into the door jam switches, they started to function. I then swapped out the dimmer switch and that let them turn on from that switch.. That's when I probed the overhead light again and saw current on the orange wire. I reinstalled the light housing and got the lights to come on, although I'm not sure if they're functioning properly. Small victories!

Can door jamb switch also keep overhead light from turning off? That's my issue

 

[Erik the Awful]

Yes. The door switches are normally-closed and closing the door opens the switch. Unplug it and see if your problem goes away.

 

[Silverado68]

Hello everyone.

I'm trying to track down an odd issue with my beater truck. It appears that the over head map lights/dome light don't work and the lower dash curtsey lights & glove box light are constantly hot. I will start with, I have downloaded the great wiring diagrams that are posted in this site. After a bit of studying them on Sunday, I realized that the 30A circuit breaker fuse was missing, so I got one of those and still have no over head lights. I replaced the bulbs and checked with a test light ( quick and dirty) and then my multimeter, no voltage going up there. I noticed that both lower dash courtesy bulbs were blown. I checked them and found that they are constantly hot ( 12V going to them).

Today I started with isolating the lower light circuit by unplugging both door jamb switches, no change- still getting 12V to those bulb sockets. I tried with all positions of the ignition key, no change. The ignition switch ( on the lower steering column is new, as is the ignition switch/key. Both were so worn out when I got the truck, you didn't need a key to twist the ignition switch)

By using the schematic, I traced the wires back to the Convenience Center, both sets of orange wires are always hot. I would imagine that the circuit needed to be triggered/completed by one of the door jam switches. I haven't pulled up the door sill trim to check for crushed/shorted wires, but outside of doing that, it really baffles me how 1/2 of the circuit is dead and the other 1/2 is constantly energized. I also pulled the aftermarket deck, expecting to find a hack job of the harness but I was surprised to find some nice, neat Crutchfield style harness that plugged into the OE harness. I can't see any evidence of hackery anywhere under the dash, no chew marks from critters, no chaffing of harnesses against metal. No pinched harnesses that I can see. All cluster lights work along with the dimmer. When I "click" it to the interior light position, it get nothing.

If anyone has any ideas on some more in-depth trouble shooting, I'm willing to try anything.

This is uncanny, I’m experiencing this exact same phenomenon and have done everything that you’ve stated thus far. I removed all the interior trim to redo the headliner so I was also able to trace the wiring from dome to dash and found no wire breakers or grounds

 

[Silverado68]

Do u have pictures of those wiring schematic? Can u post them.

I realize this post is 5 months old but if you still need schematic I own all the maintenance manuals for the 94” models

 

[J_T_Beal]

Hello everyone.

I'm trying to track down an odd issue with my beater truck. It appears that the over head map lights/dome light don't work and the lower dash curtsey lights & glove box light are constantly hot. I will start with, I have downloaded the great wiring diagrams that are posted in this site. After a bit of studying them on Sunday, I realized that the 30A circuit breaker fuse was missing, so I got one of those and still have no over head lights. I replaced the bulbs and checked with a test light ( quick and dirty) and then my multimeter, no voltage going up there. I noticed that both lower dash courtesy bulbs were blown. I checked them and found that they are constantly hot ( 12V going to them).

Today I started with isolating the lower light circuit by unplugging both door jamb switches, no change- still getting 12V to those bulb sockets. I tried with all positions of the ignition key, no change. The ignition switch ( on the lower steering column is new, as is the ignition switch/key. Both were so worn out when I got the truck, you didn't need a key to twist the ignition switch)

By using the schematic, I traced the wires back to the Convenience Center, both sets of orange wires are always hot. I would imagine that the circuit needed to be triggered/completed by one of the door jam switches. I haven't pulled up the door sill trim to check for crushed/shorted wires, but outside of doing that, it really baffles me how 1/2 of the circuit is dead and the other 1/2 is constantly energized. I also pulled the aftermarket deck, expecting to find a hack job of the harness but I was surprised to find some nice, neat Crutchfield style harness that plugged into the OE harness. I can't see any evidence of hackery anywhere under the dash, no chew marks from critters, no chaffing of harnesses against metal. No pinched harnesses that I can see. All cluster lights work along with the dimmer. When I "click" it to the interior light position, it get nothing.

If anyone has any ideas on some more in-depth trouble shooting, I'm willing to try anything.

Where did you find the schematics on this site?

 

[Firewood truck]

This is uncanny, I’m experiencing this exact same phenomenon and have done everything that you’ve stated thus far. I removed all the interior trim to redo the headliner so I was also able to trace the wiring from dome to dash and found no wire breakers or grounds

Where did you find the schematics on this site?

I honestly don't remember where I got them on the site, I think tat one of the other members gave me a link to the schematics but they are a "sticky" somewhere in here. I know that doesn't help you very much.

As for @Silverado68 , have you tried running a jumper cable ( or use a power probe) from a know 12V hot directly to the overhead light, or test for voltage going up to the lights? Once I did that, I was able to narrow down the area to look for problems, and when I pulled the kick plate up I found the broken, corroded wire that was causing me so much grief.

Sorry for the long time to reply, I'm not in here very often. I've only returned because I need to figure out what to do about the dead engine in the truck.

 

[df2x4]

Where did you find the schematics on this site?

The thread is called "'88-'98 Service Manuals" and it's a sticky at the top of the "Engine Performance + Maintenance" section. Here's a link. If you don't see the year you need in the first post keep scrolling, other members have added the missing years.

https://www.gmt400.com/threads/88-98-service-manuals.43575/