Brake/Turn light simultaneous

[Spidey300]

98 XL 2.5L fleetside. Truck failed safety bc brake lights weren't working properly. Got home & realized that I had the wrong bulbs in the upper amber turn lamps. I had 2 filament 3157 instead of single filament 3156. Switched out and now I cant remember how they are supposed to properly function.

When I press the brakes, both my red middle brake lamp and amber upper turn lamp illuminate. Turn signals work just fine on their own, backup/reverse, etc. Only time brake light comes on it's own is with hazards and with headlights on. Is this normal? I cant remember or find any info.

A few months ago I noticed that the turn signal would start going really fast when I hit the brakes but would be slower whe I wasnt on the brakes, not sure if that's related or not. TIA

 

[Uncle Gump]

Do you have trailer wiring?

 

[Spidey300]

Do you have trailer wiring?

No. I wired a 3rd brake light for my camper shell about a year ago but this just started recently and I checked those connections and they seem fine.

 

[RonD]

1998 Ranger uses 3 wire setup, 1993 to 1999
There is 1` brake light wire to the rear, comes from the brake pedal switch, it splits at the rear and runs to the 2 rear brake lights, this is a dual filament bulb, other filament is for Park lights and its a dimmer filament. that the brake filament

Then there are 2 wires, one for left turn bulb(single filament) and one for right turn bulb, these are the amber colored lenses, these come from the turn signal stalk, multi-function switch

That's what the "3-wire" means

1992 and earlier and 2000-2011 Ranger used 2-wire setup, turn and brake share 1 wire(and filament) on each side, the brake and turn were combined in multi-function switch


It reads like you have a crossed wire some where, or...........the brake light is using the Turn bulbs for its Ground
Turn bulbs would be slightly dimmer than "normal" if brake lights were using them as a ground

 

[Spidey300]

1998 Ranger uses 3 wire setup, 1993 to 1999
There is 1` brake light wire to the rear, comes from the brake pedal switch, it splits at the rear and runs to the 2 rear brake lights, this is a dual filament bulb, other filament is for Park lights and its a dimmer filament. that the brake filament

Then there are 2 wires, one for left turn bulb(single filament) and one for right turn bulb, these are the amber colored lenses, these come from the turn signal stalk, multi-function switch

That's what the "3-wire" means

1992 and earlier and 2000-2011 Ranger used 2-wire setup, turn and brake share 1 wire(and filament) on each side, the brake and turn were combined in multi-function switch


It reads like you have a crossed wire some where, or...........the brake light is using the Turn bulbs for its Ground
Turn bulbs would be slightly dimmer than "normal" if brake lights were using them as a ground

Thanks. The issue started at a time when I didn't do anything different to the truck so I dont know how it could be a crossed wire. How/where would the brake light possibly be using turn bulb wire as ground? They share a ground, right? Is that the one behind the driver side kick panel. Truck appears to have a prewired trailer connector behind the spare, maybe something happened there?

 

[RonD]

Yes, as Uncle Gump said, trailer light wiring can cause many odd light issues

The tail lights are not behaving as designed, so something is out of spec, I know DUH, but that's something only you can solve
Ground was a guess and light would be dimmer

Just looking at a 1998 wiring diagram and brake light 12v DOES run to the multi-function switch but shouldn't be used as there is a direct wire from the brake pedal switch to the brake lights
So maybe the fault is in the multi-function switch
Just guess's

 

[Uncle Gump]

The 12 volt brake signal to the multifunction switch would be used for hazard lamp override. It is also a common point of the two circuits.

The other place would be the tail lamp harness connector. I would disconnect the tail lamp harness and test the lamps functions there. If they both light up there... multifunction switch would be suspect. If they operate correctly... the problem is after the connection in the harness.

 

[Uncle Gump]

Wait... on that truck with separate bulbs for brake and turn... it isn't a hazard lamp override input.

I would still disconnect the rear lamp harness and test there.

 

[Spidey300]

Wait... on that truck with separate bulbs for brake and turn... it isn't a hazard lamp override input.

I would still disconnect the rear lamp harness and test there.

Havent had a chance to check the truck itself yet but looking through pics I took while the bed is off, I may have found the issue. Looks like a broken black wire on the front end of the tail light harness. Will confirm

 

[Spidey300]

That was it! Broken ground wire on the male side of the tail light harness connector. Broke right at the connector so I had to de-pin it to crimp on an extension and re-pin, which was a bit of a pain, but now it all works properly! This is why I take random pics of my truck, lol! Thanks guys!

 

[Uncle Gump]

Thanks for the follow up...

 

[Uncle Gump]

Just add to the topic here...

Whenever I have tail lamp issues... that a bulb or two don't fix. My first move is to always isolate the problem by disconnecting the rear lamp harness and testing functionality on the truck side of harness. It will always tell you where the problem isn't.