Internal lights switch to LED's issue

Maintenance/Repairs
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1

I’m converting my internal lights to LED’s. I’ve done this on 2 previous cars without a problem. In my Jetta I’ve replaced:
mirror lights
backseat reading lights
front driver and passenger foot lights
trunk light
rear license lights

  • I have not replaced the front seat reading lights

After every installation I tested each light and they worked. Recently, I noticed that all but the front driver and passenger foot lights and license plate lights were the only ones working!

I checked the fuses and they were ok, even switching with another of similar amps and the switched out fuse worked in another spot just fine.

I replaced the ECU about 6 months ago and hope that it’s not that. Any ideas? Any other trouble-shooting I might try? Should I start putting back the old bulbs to see if they work?

2

I don’t know. The only ones I changed out were my mower head lights and that worked fine. In the past though I have read cautions about using leds but don’t remember why anymore. One thing I think is greater heat. The ones you are having trouble with may be on more than a reading light would be and maybe distorted the socket. So guess I’d just check the sockets and put the standard bulbs back in.

3

The replacement bulbs probably use significantly less on-current, I’d expect that to be compatible w/the car’s existing wiring and connectors, but if any associated circuits measure the circuit current to determine the lighting status, that might confuse the electronics. Some LED bulbs for automobiles are purposely designed to increase their current level, at least partly for this reason. And b/c LED’s are directional, current only flows one way, some car-versions are designed to be bidirectional. Are the bulb versions you used like that?

4

Put the old bulbs back in. It’s going to be less trouble in the long run.

Your vehicle’s electrical system may not have been designed for the extra current draw, etc. that LED bulbs require.

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5

I would think the LED’s draw lot’s less current. I’m not sure how I’d check for LED’s that are designed to increase the current draw. The bidirectional is such, that if you put the bulb in the wrong way it won’t work and you have to just switch it around and it works. I did try each of the lights after putting in the bulbs and at one time they all were functioning correctly.

6

I’ll try putting the standard back in, but they LED’s are known for creating a lot less heat than the incandescent bulbs. That’s why in your house you can touch a lit LED light, but not the other.

Thank you for your input

7

Why bother doing this? I’ve never had to replace an internal bulb, except for a dome light bulb, I keep my cars 10-15 years.

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8

The only bulb I’ve replaced were the license plate bulbs. Put the same bulbs in. Don’t see the need at all for leds.

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9

I have replaced every interior, and every tail, turn and reverse light on my truck with LED’s and wow what a difference it makes, it is recommended to install them with the battery disconnected, but I made sure that no power was going to any of mine when swapping out and I had no trouble, but others have blown up to 3 fuses by doing it wrong, so check ALL your fuses and not just the one you think it takes… And only the map lights were bidirectional… Next I will change out the tag lights to LED’s but they are a bit of a PIA (kinda) to replace…
Also watch for cheap LED’s as they can cause issues, so make sure you buy good quality ones…

For anyone that is interested PM me for a link to a guy who is a Vehicle Design Engineer and explains the differences in the H11/H9 headlights and looking at the differences between HID, LED and Halogen light sources for use in the Tacoma… Very technical stuff…

Yes LED’s do not put out near the heat of a standard bulb… and yes they draw less energy, about 75% less energy with all things being equal…

https://www.energy.gov/energysaver/led-lighting

10

Pay no attention to me. I’m just a pin-head diyer. My only LED experience is when I changed my Corolla’s dome light to an LED version, which I must say works great. Cooler operation & much brighter. But the current draw issues might be mentioned by inference, on the product packaging, something like “compatible with most turn signal blinker relays”.

11

Best guesses: Either the bulbs vibrated loose or they were of poor quality and blew.

12

I asked a neighbor who is an Electrical Engineer, and he said that if the LEDs draw a lot less current than the old bulbs did, the Can Bus will be “confused”, and may interpret the situation as burned-out bulbs.

13

He is the wrong type of engineer.

Controller Area Network is a method of communication between modules, there are no light bulbs involved.

Interior lights are controlled/monitored by the body computer or other similar module.

14

Doesn’t the Can Bus communicate with the BCM?

15

Body computers have fault detection capabilities. If the expected load (amperage draw) on a circuit is incorrect, the BCM may determine a fault has occurred and disable that circuit until the problem is resolved.

A fault detected by the BCM will not affect the operation of the BUS communication network, the BCM will be able to communicate with other modules.