For some reason when I press the brake pedal my sidemarkers light up. This only happens when the lights on the car are completely off; if even the parking lights are on, everything works normally.

I met up with Thermo last Tuesday in Rochester and he narrowed it down to an issue with the tail lights. So today I went out and messed around with them to see what I could figure out.

First I unplugged the large connector from the back of the right hand tail light. I tested and everything worked normally. So, I plugged it back in and started testing individual bulbs by simply removing them one at a time. Once I removed the brake light bulb, (top most bulb) everything worked normally.

Then I tried replacing that bulb with another in case it was defective, but the same issue resurfaced. Next I tried replacing the entire bulb plate with a spare that I had from an extra tail light assembly, but the issue was still there.

So I put everything back together the way it was on that side and started tinkering with the other side (left hand side). I found that if I removed the brake light bulb on that side everything went back to normal as well. I don't have a spare bulb plate that I can test over there, but I'm guessing that wouldn't change anything.

Therefore, the result of my testing was that for some reason if a brake light bulb is removed from either side then the sidemarkers operate normally, but if both are in at the same time there is an issue.

I should add that all the bulbs on my car are LEDs at this point, and that when the sidemarkers illuminate during braking, they are much dimmer than normal.

Perhaps I need some resistors for my brake lights as well?

I'm lost at this point so any advice would be appreciated!

 

Evan, based on what you are saying, you have a problem with the LED light bulbs allowing a small amount of current to backfeed into the parking light circuit. A single bulb can not provide enough current to cause your LED side marker lights to light (they are still getting power, but not enough to cause the LED to light since it needs a minimum amount of current to cause this to happen). So, from the sounds of things, you need a different set of LED light bulbs that do not cause a backfeed of power. The other option is you install a diode (3 amp rating minimum) in the circuit for the parking lights to prevent this back feed.

If you need me to go into more detail, let me know.

 

Is it possible that there was a diode like this within the electrical system that I fried when I accidentally arced the battery?

It just seems odd to me that this would coincidentally happen immediately after that incident and not be related

 

Evan, it is possible that the arcing did hurt the LED bulbs. But, if you did anything to the computers in the car, it would be causing what you are seeing even with the tail lights removed from the car.

 

I didn't forget about this thread, I'll be testing with the regular bulbs at some point this weekend and I'll let you know what I find.

 

Don't mean to thread jack but I have an issue almost the same . When I press the brakes the lower amber lights come on also with the brake lights . When I put the car in reverse with no headlights on the reverse light fuction normal but with the headlights on they don't work . The lights that come on are the amber ones . What could be the issue ?

 

Smitty, it sounds like you have a problem with the plug to the tail light housing. You will need to pull the tail lights out and then do a detailed inspection of the plug and the associated pins. I bet you will find that there will be some significant corrosion in there. You may also find that a pin has been damaged (bent over possibly) and that is also leading to what you are seeing.

If you need me to go into more detail, please state the year of your car and I will see what I can find for you.

 

You're the man Thermo! I finally got around to testing the brake lights with the standard bulbs and everything worked perfectly!

I'm ordering some new LEDs right away, I guess I must have fried the current ones when I arced the battery. I wanted to get red LEDs anyway since I think the whites look too pink in the tail light housing, now I have an excuse

 

It is an 2002 X Type 2.5 ltr .

 

smitty, I would start with pulling the plug on both tail lights. Now, when you step on the brake pedal, does the amber lights light up? If they do, then your problem is in the wiring harness of the car (write me and I will assist from there).

If the amber lights don't light up, then do a detailed inspection of both plugs and their recepticles. Do all the pins look in good condition (silver in color, not major signs of rust)? If not, use a scribe/sharp tool to clean up the pins to restore them to a shiny silver color. If you have corroded pins and the pins are simply gone, then odds are you are looking at having to replace the backing to your tail lights (let me know, I may be able to help out).

Once all the pins look good, what you will need to do is to remove both tail lights, remove the backing plates off of both tail lights and plug them back into the plugs removed earlier. Now, remove all the bulbs from the taillight backs. Step on the brakes. Do the amber lights light up? If yes, then your problem lies in the backing plate, disconnect one, retest, if still lighting up, disconnect the other one and reconnect the original and retest. The backing plate that causes the side amber lights to light has an internal failure and you need a new backing plate.

If the backing plates do not cause the amber lights to light, now install the stop light bulb on 1 side. Step on the brakes. Do the amber lights light? If yes, then you are either not installing the bulb fully or you are using the wrong bulb for the brake lights. If the amber lights do not light, install the stop bulb for the other side. Did the amber lights light? If yes, then that bulb base has an internal issue or you are using the wrong style bulb on this side.

At this point, you should have found the issue causing your amber lights to light and your backup lights to not light when the headlights are on. If it hasn't, let me know and I will give you a few more checks to do.

 

Thanks I just looked at the connectors and both of them have melted the plastic causing power to be feed to the other lights . So now I need a connector .

 

smitty, finding the plastic connector is going to be fun (I do not mean this in a good way). No one I am aware of sells just the connector. Even going to Jag, they will tell you that you need to buy a complete harness which is going to get you back quite a bit ($300 or so more than likely). With that being said, you may want to check out the local wrecking yards and see what they want for the harness. Whether you take just the plugs or the whole harness, they are going to charge you the same price. So, you might as well get a complete harness and swap the whole harness to prevent issues in the future with sliced wires (seems to be a common problem area I have found when not done to exact standards). I know this is not the answer that you were looking for, but I have done a lot of looking for various plugs and I always seem to end up at the same conclusion.

 

Smitty, are you looking for the large connector for the tail light assembly?

If so, I think I have one from when I ordered a used tail light assembly on eBay. It's in storage right now but I can check tomorrow.

Also, another option would be to buy a used tail light assembly off eBay. You can get them for ~$60 and they usually come with the connector and about 6 inches of wiring. Just ask before you bid/buy, or even ask the seller if they'd give you just the connector. Most of these guys are wreckers or people parting out cars.

 

All I need is the connectors . I should have given you all my backround info in my first post . I'm a motorcycle service technician my previous job was helicopter technician . I was just lazy in finding the problem with the lights .

 

@smitty: Sorry I don't have any connectors, I thought I had at least one but I must have returned it or something. Like I said though, an alternative to paying Jag $300 for your connectors would be to get them from the guys on eBay who sell the used tail lights. Even if you have to buy the entire tail light, they are usually around $60 used.


@Thermo: I got some new LEDs in yesteday, I put them in the tail lights and instead of fixing the problem it got worse. With the new bulbs in, not only do the same issues happen when you hit the brakes without the headlights on, but now the headlights also turn on. Also, the third brake light is always on with these bulbs in. However, I'm running the normal bulbs now without a problem.

I'm still thinking I fried something in the car which is allowing the excess voltage not used by the LEDs to backfeed into other systems.

 

Evan, not sure what to tell you then. Odds are, your best bet would be to take it to a shop and have them test out the rear of your car. Otherwise, you are looking at making your own custom tail light bulbs which is possible, but if you don't have the electronic background, can be a very frustrating thing too.

 

Thermo, I was thinking of trying out some resistors. It seems to me that the only difference between the bulbs that work and those that don't work is the amount of power they draw.

I'm assuming I fried something in the car somewhere that prevents backfeeding of excess voltage, but it seems to me that if the proper voltage is drawn then this isn't needed. Perhaps the part that I fried was in place to prevent backfeeding if one of the bulbs blows out.

Any recommendations as to what type of resistor to use? I have 4 of these in place for my turn signals and they have been working great for 4 months now:
LED Car Light Bulbs - Load Resistor, LED turn signal lights Equalizers

Would that be adequate for the brake lights? I was thinking I might even need two per light since there is a separate wire for when the brake is actually pressed and another for the more dim illumination at night.

Let me know what you think

 

Evan, you do have an interesting idea. Not sure how well it may work, but looking at things, if you can, find a 25 ohm/10 watt resistor. You should only need 1 of these. Now, for simplicity, you can remove any one of your side marker lights. Initially (before you go cutting the wiring all up), push the wiring into the back side of the bulb base, making sure to run the resistor in parallel to the bulb (ie, one wire of the resistor to the colored wire, the other wire of the resistor to the black wire). What this is going to do is any small currents that are being fed back into the running light circuit will be filtered to ground via this one resistor. This one resistor should be able to ground all the power in question and fix all 4 of the running lights.

You can use the resistors you are talking about and wiring them up just like I said with the 25 ohm resistor. The only difference is you are going to be putting a heavier load on the alternator (2 amps extra vice half an amp). But, the lower resistance piece is going to be more likely to fix things if this does correct your issue.

On a side note, if this does fix the issue, when permanently installing the resistor, make sure to mount the resistor to a metal piece of the car. You want to make sure that the resistor has no chance of coming in contact with either the wiring or the plastic parts of the body. I would hate to see you damage something else on the car. The resistor that you have the link to is going to generate almost the same heat as a 40 watt incandescent light bulb does. It is going to make things nice and toasty. The one I recommend is only going to pull about 10 watts. Much more friendly to the body of the car.

 

Thanks for the reply. I will try to find a resistor that matches the specs you mentioned, I was also concerned because the ones I have generate enough heat as it is and they're only on intermittently when I use the turn signals. Having that much heat on constantly when driving at night/braking might be an issue.

So you think I will only need one resistor? If that's the case then I'm assuming it would be connected to the tail light wire (the one that's always on at night) and the ground, correct?

As for a permanent mounting point, I was thinking in the trunk on the left side where there is a large recess behind the carpeting.

 

Evan, no, you want to connect the resistor to the running lights as this will "sink" the current to ground. Granted, you may find that running one for the 3rd brake light might be beneficial too. Just the 3rd brake light is a little harder to get too. So, I would start with the side running lights and then see what you have at that point.