Eastman51

I went out and bought some nice Sylvania Zevo 2375R LED bulbs and installed them in my car. Already a dramatic improvement in both lighting and power draw. My voltmeter stays locked at 14v with the headlights and fog lights on while stepping on and off the brakes. However, the super low resistance of the LED bulbs has tripped my "STOP LAMP" warning light. I'm quite certain the checker works fine since the light was off before I switched to LEDs. I know that when I bought the car, it had a blown brake light filament in one of the bulbs and the warning light was on; replaced the bulb and it went away. Traditionally you would just add resistors to fix this, I think; however that just increases power draw, exactly the opposite of what I was trying to accomplish with the swap. Is there a way to get the "stop lamp" light to function as intended (notify you of burnt bulb) with LED brake lights? I would rather not remove the bulb/checker as its a pretty neat feature that even my daily driver doesn't have.

For context, I just recently installed some halogen fog lights on my 83 FB a couple of days ago. They work great and I love the look. However, the increased draw from the halogen lights puts a pretty large strain on my alternator. I noticed that when at a stop with my foot on the brake, the headlights and fog lights on, and my turn signal on, my voltmeter was reading just barely over 12v. I swapped to a 70 amp S4 alternator last year when I switched to a dual alternator belt pulley for the air pump delete. Hence the LED brake light swap. I swapped to LED marker lights a while ago because I thought the incandescent markers were too dim. I plan on following a writeup here on the forums to also swap to LED signals for even lower draw. But for the time being, I would like to return the "stop lamp" light to its intended function without using resistors or converting back to incandescent bulbs.

I could not find anything conclusive on Google, or here on the forums, regarding LED brake lights and solving the "stop lamp" light. I hold hope that there is a better way than resistors, but I lack the know-how to figure that out on my own.

Maxwedge

iTrader: (1)

Subscribed. I never new the car had a warning light for burnt-out tail lights. Cool stuff.

Eastman51

I did some research while at work today, and talked to my coworker. It is exceptionally unlikely that there is a way to trick the computer into thinking its got regular bulbs without adding resistors. I didn't want to add any, but it seems that I will have to. From my limited understanding, adding resistors shouldn't put amp draw back up to the same level as on regular bulbs; but will still slightly increase amp draw.

Based upon my math, 8 ohm 50W resistors should be adequate; though I would like even higher wattage to reduce heat. Soldering them in should be a fairly easy task after removing the tail light assemblies from the car. As for mounting the resistors, I am not sure what I will do. I have some leftover thermal adhesive from a PC project a while ago, but that would make removing the assemblies in the future impossible without cutting wires..... Not to mention, all the insulation back there would be a fire hazard if the resistors put off too much heat.

After checking the 83 FSM wiring diagrams, I'm not quite sure what the forum writeup is referring to in regards to switching to an electronic flasher. Will be looking up the 84 wiring diagrams to compare and see if I can figure it out. I definitely do not want to add resistors to the turn signals.

I have not seen any other threads with usable information for what I am attempting here, so I am just going to have to fumble around in the dark until I make it work. Hopefully this thread can be of use to someone in the future.

Eastman51

I am not sure if the S3 cars have it or not, but my S2 has it for sure.

Toruki

The LED bulbs you bought reference a "load equalizer", i.e. a big *** 6Ω 27W resistor in their Amazon page



Although a 50W rated resistor will run cooler.

Edit:

If you are interested in more qty than just the Amazon 2 packs at $15, then DigiKey is good if it's worth the shipping and you get a nice 50W rating.

https://www.digikey.com/en/products/...FB6R00/1646199

Here's a digikey search link:
https://www.digikey.com/en/products/...ZBD7mntsaRZWSA

Benjamin4456

DigiKey is awesome.

So easy to waste away money on that site... I mean what, it's definitely all well spent. I needed that thingamajig for... for science!



Seriously though, they are a great resource for lots of things electrical/computer along with Mouser, ST, Arrow, etc. Although I'm a little partial to DigiKey. Shipping is usually pretty reasonable as well.

shetlen

iTrader: (2)

I just switched to all LEDs' in my 1982 GSL but I don't have this issue. The stop lamp still works as advertised, I am using the same 2357R's from O'reillys. My FD on the other hand does have issues running them and never completely turns off.

Eastman51

huh, that is odd. My 83 was showing the stop lamp bulb until I wired in resistors. Strange that your 82 seems to work as intended without wiring anything.

Natey

iTrader: (19)

Most LEDs these days come with a built-in resistor. At least that's what I found while researching headlights for my Mazdaspeed Protege. Not sure about tail lights, but pretty much all the headlights came with a resistor.

saltwalker

I had considered replacing all my bulbs with LED's but hadn't even thought about it tripping the warning lamps. I was concerned about the hyper flash condition that according to the bulb manufacturer can occur. They recommend a resistor to correct the issue but I didn't want to deal with that so I cleaned up my ground connections and did a alternator upgrade to a 130 amp (direct bolt on). The cleaning up of the grounds really helped more than anything but the additional output of the alternator stopped the dimming of any lights under a heavy load.

Eastman51

Yea, I plan to convert to a 3 pin flasher to prevent hyperflash myself. I should probably clean up all my grounds to be honest, excellent idea.

​​​​​​ Something I've noted, howeve, is that I've never really noticed my lights getting dimmer, even on the stock alternator and before the led tails on the S4 alternator.

Frogman

Why do you even need LED lights for the rear lights? A traditional bulb already meets SAE specs for safety and can last ten years , i mean I plan on doing an LED headlight swap for my car but the rear lights look bright enough

Ckforker

I'm with you Frogman, the PO did all LED on my car and that was one of the first things I did.

I could maybe see the side markers, but that would be it. The lights, sans headlights don't draw that much from the alternator.