Parking lights work with my brakes

As the title suggests.... My parking lights come on, when I hit my brake lights. It’s like I have front brake lights.....might actually be kind of a cool mod, however this was not intentional at all. I used to have glitchy headlights and my parking lights would come on with the brakes.
I swapped my headlight switch with a junkyard one. Was hoping it would fix both because I noticed both at the same time, assuming they were related. Headlights work fine now, but my parking lights still come on.

I only switched out the lever on the headlight switch.

am I just dealing with electrical gremlins that I have to chase down?

 

yep, sounds like a ground shorting. by "parking" lights do you also mean the rear as well as the marker lights in front or is it just the marker lights in front? if so, i'd inspect those connectors. see if it still happens when you disconnect each one.

 

^^^^^^yep. check your grounds.

 

Ya Parking or marking Lights or whatever they’re called. I’m not sure about the rear, I haven’t noticed that. I never noticed “marker” lights in the back to be honest hahaha

I had different issues In The 85 from a bad ground. I hoping, maybe this was a switch problem. Anyone know how many grounds there are to check on the truck?

 

Check the light sockets where the brake and tail lights share the socket.

If the tail lights are not coming on you have more problems.

Unless your tail light harness has physical damage and the wires are touching

 

The parking lights get power from the tail light fuse.
The tail lamp fuse gets power from tail lamp relay.
The headlight switch activates the Tail lamp relay.
The parking lights should not come on with the headlights in the OFF position.

I’d pull the tail lamp fuse, press the brake pedal and see what happens.

 

Tail lights work and headlights work

 

awesome, that’s very helpful, I was looking the the FsM to try and find a similar breakdown.
Parking lights only come on when I hit the brakes *if the headlights are off* if my headlights are on, obviously, the parking lights are already on

everything else works just fine, and I recently noticed when I was parked In Front of some glass that those lights come on with my brakes

 

Oh oh oh, you know, now that I’m thinking about it in those terms, the PO had wired up a trailer plug for brakes and everything to a trailer. I’m gonna poke around that wiring and see what’s going on. It was definitely a DIY wiring

 

... be 100% sure you have the correct size bulb in sockets. Have you recently changed out any ??

 

I had changed my turn signal bulbs probably over 3 years ago. I don’t think that this has been going on for that long. Last year or maybe 2018 my headlights started getting glitchy and around the same time I noticed the parking lights coming on when I hit my brakes

 

I’m gonna check the trailer hitch wiring, and then tail lamp fuse like was suggested. I’ll post what I find when i get it fixed

 

So I noticed this morning on my way to work, my clock also dims down when I hit my brakes. But only if my headlights are off, same as my parking lights. Does this help in leading me towards a bad ground or a base fuse or relay?
thanks for the help.

 

The clock is connected to a 10A Panel fuse.
The Panel Fuse is also Powered by the Tail Light relay.
The dimming may or may not be associated with your issue.

I do believe however, you are on to something with the trailer wiring.
Trailer running lights would be hooked to the tail lights.
And the trailer brake lights would be hooked to the brake lights.
I’d definitely start there.

 

thanks, thats good to know. Do you have a FSM? if you do you are obviously better at finding things in it than me

 

No FSM, just an Electrical diagram (for a 99’)
I some how got it off a link on a google search, from .AutoZone. of all places.

 

I had this problem on 2 trucks over the years. Both the same problem— tow harness installer uses crappy connectors up behind the tail lights, the ground connector eventually breaks due to rot/corrosion. Trace the ground wire that begins at the brake/marker lamp socket on the assembly, you will find the problem quickly. Could be in either tail light. If you doubt it, hook a jumper from the socket shell to a good ground and your problem will (temporarily) go away. Second check- remove the bulb and it will also go away.
Don’t waste your time with fuses and the switches/relays.

 

Checking it out today, thank you. That will help in my searching for the connections that were made for the trailer harness.

 

well since it wasn’t a huge issue that my parking lights came On With my brakes, i hadn’t taken the time to start poking around the trailer harness hookup.

With that being said, when I backed up to my house last night, I realized that my brake lights actually aren’t lighting up if I have my headlights turned on. If my headlights are off, my taillights(or brake lights, not sure) do light up when I hit my brakes, but so do the parking lights on the front.

I’ve completely eliminated the trailer light harness and surprisingly it was done the proper way, with matching harnesses that plug into the OEM harness.

I am at a loss as to why my lights are all jacked up.
Any suggestions other than the trailer light doohickey?

 

I would verify ground with a meter on all 4 marker lights, as well as the brake lights. This seems like a ground issue but I'd have to study the wiring diagram to be sure. Put one meter lead on the socket shell, and the other on a good frame ground/battery ground. Go through all the different lights on/off combinations and at all times the shell to ground voltage should stay close to 0 volts. If you are seeing things getting close to 12V, you know you have an issue. Problem could be at the shell or light connector, or could go all the way back to where the ground(s) for the lights ties to the body ground. These end up being at the kick panels if I'm not mistaken. There are 2 on each side.