1985 k10 horn cig dome and curtassy lights not working

[true74yamaha]

I just want to start of and say this seems like an awesome forum glad I made a profile.   My trucks an 1985 k10 lwb 305 w/700r4. I got it from my grandpa only has 30,000 original miles. 


Alright so here's my problem my horn cigarette dome and couresy lights dint work.  I went to put in a new fuse in the horn fuse spot, and it blew.  For a temp fix I have my dr side horn hooked to a wire and a push button hooked to another interior fuse for the time being. So I know the one horn works I never hooked up the Rh side horn to my temporary wire.  This was before I knew all items were linked in a circuit I went to change me dome light and it was blown and the wires to the terminals were melted on the ends. I then pulled those wires from the connector behind the interior panel. The wire was good the rest of the way down. So I cliped the ends and re did the dome light then I double checked and tested the wires they are good.  I then went to the next section threw the sill plate It looked fine I didn't see and problems with it.  Although I do know they are known to go bad.  I lost where that wire hooks to on the fuse block.  It looks like it hooks up on the top? I then went to the Orange wire off the cig lighter and I had a weird ohm rating. I'll have to test again to let your guys know the reading.  I was told on 67-72 forum that the cig lighter is suppose to have a ground wire hooked up to it.  I didn't see one is it suppose to have one? If so that could be my problem sense they are all on the same circuit.  I did go threw that Orange wire and I didn't see any spots where it was broken that I could see up until it went up by the gauge cluster and I lost it. This is about as far as I am with my truck.  Any ideas

[true74yamaha]

Any help on tracing down the problem

[zieg85]

I had the same issue with my 85.  I've had a few problems and I remember mine was a problem in the left rear tail light assembly.  One of the wires had rubbed through.  Taped it and it was fine.

[true74yamaha]

Wait and that messed up your horn? I have a periodic short in I believe my left tail light.   

[zieg85]

Wait and that messed up your horn? I have a periodic short in I believe my left tail light.

My left turn signal popped the fuse.  Lost cig lighter and top dome light and horn.  If you tried the horn you would hear the horn relay chatter and the dome light would flicker dim.  The under the dash light would still be fine...

[true74yamaha]

Awesome thank you, it definetly can't hurt to fix that bad wiring sense it needs to be done any ways. I will fit it and let yall know how it goes.

[true74yamaha]

Update on my wiring problem.  I pulled tail light lens and housing I didn't see any wiring that had a break in the sheathing.  But on a grounding wire that grounds to my taillight bucket, That area was fairly rusty. I'm pretty sure when I was testing wiring in the inside of my cab Im pretty sure I found that the Orange wire after the fuse box tested bad on my ohm reader.  And that was by my cigarette lighter.  Is there a  way to test a cigarette lighter housing? I was thinking of doing the easy test way and run a pig tail wire to my CD player that has a direct hot wire that I ran to the battery for my presets.  That way if the cigarette lighter and curtassy lights come on it will tell me if its bad or not good idea? After doing this what could I test next? I think I remember Someone saying that I could test the horn relay terminals and it would tell me where the problem lyes without going threw a mess of wiring. 

[true74yamaha]

alright well on my truck I needed to Change my battery terminal cables, while doing this I ran a new wire from the battery to my CD player.  Well I thought I'd see if  my cigar lighter was being grounded out like I thought it was. Well I ran a pig tail from my cigar lighter to the hot wire I ran as soon as I did that they sparked.  this was a sigh of relief think that I found part of my problem on my truck. Now sense there's no more light out and I can't work on my truck I'm hoping I found the only problem as to why my horn,cigar, dome and curtassy lights aren't working. 

[true74yamaha]

Can a horn relay blow when the horn fuse does? My horn isn't getting juice to it.  I don't hear any click so I don't think my relay is working.

[Jason S]

Is there power to the horn relay when you push the horn button?  If there is power at the relay, then the relay could be bad. 

[true74yamaha]

Well I thought I sourced my problem with the cigar lighter.  Turn out it was just the first part of it that was bad.  It is now replaced.


I'm thinking I better just work from front to back on my truck to trace my problem with my horn etc.   I know my left and right horns work with a wire hooked to the battery with a push button so they are good. What's next?

[Jason S]

I've read through this a bit and I'm not a great trouble shooter, but maybe this will help a little...

I didn't see/read whether you have read through the wiring diagrams.  If not, look here: http://www.73-87chevytrucks.com/techinfo/7387CKMans//Wiring/ST_352_85_1985_Chevrolet_GMC_Light_Truc_Wiring_Manual_CK_10_30_Only.pdf

The service manual for 1984 is here: http://www.73-87chevytrucks.com/techinfo/7387CKMans//Service/X8432_1984_GMC_Light_Duty_Trucks_Service_Manual.pdf
  and the 1986 manual is here: http://www.73-87chevytrucks.com/techinfo/7387CKMans//Service/X8632_1986_GMC_Light_Duty_Truck_CK_G_P_10_to_30_Service_Manual.pdf
 
I think your on the right track isolating the individual issues, as you seem to be working on.

Well I ran a pig tail from my cigar lighter to the hot wire I ran as soon as I did that they sparked.

If the pigtail was connected to the very center bottom of the lighter well and then connected to the hot wire and it sparked, then there is an issue.  The outer (chrome/bright) portion of the lighter well should be ground and the center positive (hot).  The lighter well should unscrew apart from the backside of the ashtray.  If you disconnect that, you can eliminate a culprit. 

[true74yamaha]

Dunno if I forgot to mention I replaced the cigar lighter.  It just dawned on me as I looked also at the instrument panel wiring.  My clock is also hooked to the same circuit as the rest of what I'm having problems with. that makes sense it hasn't worked sense my dad gave me the truck.  This is a screen shot of a post I found. I don't doubt anyone on here unless I know for sure other wise. Is this post true? If so that could be my problem. I know the gm columns are known for several problems.

[true74yamaha]

I was over on the 67-72 forum, I did a post about this same issue.  I was told my a member that my problem is in the #240 circuit.  The reason he said this is because my fuse pops as soon as it is put in.  I'm gonna trace it today or just bypass it run a new wire inplace of it and see what happens and if it fixes my short to ground. 

[true74yamaha]

Help please.  I pulled relay installed new fuse and it was fine. Installed new relay I purchased and it blew the fuse