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Discussion Starter #1
Hello all, i have a 87 dodge w150, and im having some issues with the interior lighting, and tail lights. When i pull the headlight switch, head lights come on, but thats it. Interior lights dont work. Cluster, ac. I put a new headlight switch, and same issue. Hows the wiring ran as far as the switch? Whats the fuse diagram?
https://youtu.be/8UXkOd5_BX0 pls watch and let me know what yal think.

Bulb thats supposed to light up the headlight symbol, and wiper symbol flashes when i pull or pull the knob. Flashes once for like a split second.. Someone help!!!!
 

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I take it you checked the fuses? Did you turn the rheostat to see if that makes a difference for the interior lights? Did you check the grounds to both?
 

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Electrical issues can be tricky but frequently they are actually simple if time consuming. Couple of suggestions:

* Get a multi-meter so you can read voltage as well as continuity.

* Get or make a long piece of wire so you can always check the ground from the battery. Test to see if there continuity between your local ground and the established ground (the ground side of the battery). Don't start by guessing if a screw head is a good ground. You can also check for continuity on the hot side between the end (i.e. the bulb) and the connector you are testing/at. Continuity means the wire is intact. You can check for (no) continuity between the hot wire (that isn't live) to ground to confirm the insulation is intact.

* Buy one or more shop manuals. There are some on eBay or your auto parts store can order one. Chilton, Hayes, etc. Try to get one that is most specific to your truck. That will have troubleshooting procedures and a wiring diagram.

* Start at one end or the other, not the middle.

You say only the headlights come on. Then remove the rear tail light lens and test the grounds (1st to the battery and then to the local ground). Good? (i.e. continuity)? Then check the voltage. If 12-13 volts it may be bad bulb(s). Pull the bulb and check the continuity.

I've driven myself nuts and finally learned to how to backtrack a problem. And it's kind of a 1 time thing. If you know you checked all the connectors along the way, you (usually) will not have to do it again.

Now what about the brake lights? Assuming they don't work: You will need to have someone press on the brakes for this test. They are not controlled by the headlight switch but maybe the key should be on. (Ditto the back-up lights.)

If a good ground and no voltage, start moving forward. Have trailer hitch wiring? Check that. On my 78 there is a connection under the truck by the transmission back-up light switch. Is it connected and no corrosion in the pins?

Next, with your manual, determine which color wire controls the brake lights, find the connector (plug) that it goes to under the steering column area or around the brake pedal. Power? Look for the switch on the brake pedal arm. Power? Next is probably the fuse. I don't know which one on you truck but there should be a sticker or check the manual. Power on both sides of the fuse?

If the fuse isn't hot (12-13 volts) you would need to then determine where the fuse gets its power. Look for cut wires and connectors, particularly where as the wires go through the bulkhead.

This can be a slow process. It might help to look at all electrical "systems". What else is not working? That may identify a common fault.

Good luck and apologies if this is old info for you. My fingers got chatty. Grady
 

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Discussion Starter #5
no the info is just fine. I have a tester, and I will be doing said testing. I need posts like this!

I'm going to check the fusible link to see if that has any problems. my brakes do work, and it does have trailer hook up, and nothing. I guess the fusible link goes from 1 wire, to multiple wires? side markers, and running lights? I know theres a fusible link right by the battery, is there any more? and heres the bulkhead? I assume its right by the brake booster? I cant seem to remove the tail light plugs. is it a twist lock?
pls respond
 

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Just to break it down a bit:

Do you have a tester that reads both DC volts and continuity. Couldn't tell from the one on the YouTube video.

Can't help with the fusible link. Not sure what it controls on your truck. Unlikely it's the problem.

Are you saying the brakes work (they stop the truck) but the brake lights don't work?

Assuming the bulbs have a round base, it's press in and turn and they should pop out. Are they corroded? You may need some penetration spray to loosen them up.

On my older truck and I think yours, there is a roughly 4"x4" black plastic area to the right of the booster (looking from the front to back). These are the connectors for all/most of the wires that go through the bulkhead/firewall. The connectors (on older trucks anyway) can melt, corrode, fail resulting in little or no power getting though. This can effect separate wires - some work and one/some do not.
 

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https://youtu.be/DU-zlw3B3R8 watch the video, checked fusible links, and they are all good. Next stop is the bulkhead connector.. How do i get it off?lol
There's a pic of 76 in the amp bypass link (googl_ for many others), see if they're same/similar; assuming it pulls (pries) straight off, unsure though.

... In other thread I think I mentioned my 90 developed various wiring problem, wiring and connectors on dr side wheel well were failing/bad/weakened, most likely due to batt venting/fumes I've been told (seemed kinda a common issue around here); lift up the flap there and inspect/check underneath too (wires entering connectors were barely hanging on, were not allowing proper current thru etc, or connector/s eaten/corroded and not contacting properly).
 

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im having some issues with the interior lighting, and tail lights. When i pull the headlight switch, head lights come on, but thats it. Interior lights dont work.
The headlights working tell you the switch has power going it. Look at a wiring diagram and see what wire is for the running/interior lights on the switch. Start there and work towards the non working lights to see if you have power.
 

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Discussion Starter #12
so it ended up being the headlight switch. even though it was brand new! when I pull the knob very slightly(before it clicks into park light mode) the bulb that indicates park lights come on, side markers come on, turn signals and park tail lights come on! when I go into headlight mode, same thing. I have to pull it slightly for all lights to come on. the cluster lights come on, but they are super dim, like its not even worth them being on, its so dim, and I put the led bulbs in. I might take off them blue caps in the cluster, and see if that makes a difference. heater lights come on just fine, and the led in that makes it look sweet.

I cant believe that the headlight switch being brand new, is faulty. its "standard products" its a red box, you know the brand, but it does seem to be a lesser quality than the oem one. that one stopped working as the led bulb don't even flash. going to buy a switch from AutoZone, and hopefully its a better brand, and quality than the one I have now. thanks guys for your help! stay tuned for my build thread! its going to start getting good now!. 87 w150 street/build thread. subscribe!!!!!!!
 

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Better put relay on those lights. See prior thread(s) on subject.
 
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