Indeed, the problem is that that resistor is dissipating a lot of heat. In a real bulb that heat is mostly dissipated though the glass and into the air around the bulb with very little conducted back into the connector via the thin wires inside the bulb. A “CANBUS” LED bulb on the other hand has this extra resistor (or more than 1) mounted on a PCB, often right next to the connector and with thick copper tracks conducting heat back into the connector.
I’ve seen bulb holders overheated far more with LED bulbs than normal bulbs. This extra resistor is only fitted to “CANBUS” compatible LED bulbs, just to make the LED bulb take extra current to fool the bulb failure monitoring system in some cars that otherwise would think the bulb has failed. Now, the bulb monitoring system has absolutely nothing to do with CANBUS, there were bulb monitoring systems long before CANBUS, i’m pretty sure my Sierra had it. CANBUS is a digital communications bus system that links different ECU’s in the car. You can have a CANBUS system without bulb monitoring and bulb monitoring without CANBUS I don’t know how LED bulbs with the extra resistor came to be called “CANBUS” compatible , probably some Chinese misunderstanding. Even if you car does have bulb failure monitoring it’s only going to be on the exterior lighting, not the interior light or dash illumination. So, for using CANBUS LED’s in a older car (or indeed any car that doesn’t have bulb failure monitoring) i always remove the extra resistors. They are usually the largest ones and , right next to the connector and connected directly to it, there will be smaller resistors for limiting the current to the actual LED’s themselves. As an example i just bought some T5 bulbs with 12 LEDS on them in total. When i measure the current on a 12Volt supply they take 0.173 amps which using ohms law is 2 watts Once i remove the 2 x 24 ohm resistors that are on there just to fool the bulb out systems, the current is only 0.073 amps, only 0.876 watts The bulb will work exactly the same in a car without bulb monitoring, it just doesn’t waste a lot of energy as heat which will damage the connectors and also the LED’s themselves. The situation is even worse on larger bulbs where the extra resistors have to draw enough current to fool the bulb failure system into thinking that a 21 watt bulb is still there. I appreciate not everybody is good with a soldering iron but you just need to heat up one end of the resistor with a blob of solder, once it melts move to the other end of the resistor, alternate a few times so both ends are molten at the same time and then the resistor should slide off. There are quite often one on each side of the PCB. Or, you can carefully break up the resistors with a pair of wire cutters. In the attached picture the resistors you want to remove are labelled 221 (interestingly the picture from Amazon shows them as 221 = 22 ohms whereas the ones i received are 241 = 24 ohms) One on each side. If you have any bulbs and you aren’t sure which resistors are which , send me a picture. Your bulb holders will thank you. Rant over. Jim From: Ian Harrison Sent: Thursday, July 8, 2021 10:58 AM To: quantumowners@googlegroups.com Subject: Re: [Quantum Owners] "CANBUS" LED bulbs in older cars. >From what I’ve seen, the only thing that makes them CANBUS compatible is a >built in resistor fooling the computer into thinking it has a working filament >bulb. Ian On Thu, 8 Jul 2021 at 10:30, Jim Hearne <j...@quantums.info> wrote: Has anybody seen any articles on why you shouldn’t use “CANBUS” compatible LED bulbs in older cars. Or, at least not without modifying them first. If not i may write one. Jim -- -- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To post to this group, send email to quantumowners@googlegroups.com To unsubscribe from this group, send email to quantumowners-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/quantumowners?hl=en IMPORTANT NOTE: All information presented herewith is provided on an "As Is" basis, without warranty or the implication thereof. Neither the Quantum Owners Club nor the individuals associated with the Quantum Owners Club or in the preparation of the above information shall have any liability to any person or entity with respect to liability, loss, or damage caused or alleged to be caused directly or indirectly by the instructions contained within this or related message(s). --- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to quantumowners+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/quantumowners/F44220D26B3F41C885671250AA70D95B%40JimQuad. -- -- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To post to this group, send email to quantumowners@googlegroups.com To unsubscribe from this group, send email to quantumowners-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/quantumowners?hl=en IMPORTANT NOTE: All information presented herewith is provided on an "As Is" basis, without warranty or the implication thereof. Neither the Quantum Owners Club nor the individuals associated with the Quantum Owners Club or in the preparation of the above information shall have any liability to any person or entity with respect to liability, loss, or damage caused or alleged to be caused directly or indirectly by the instructions contained within this or related message(s). --- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to quantumowners+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/quantumowners/CAPXHwq%3Dz8O5OSYBOYx_BXNg%2B3qgJ7OGzjg7pcTVrro%3D1ptK9%3DA%40mail.gmail.com. -- -- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To post to this group, send email to quantumowners@googlegroups.com To unsubscribe from this group, send email to quantumowners-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/quantumowners?hl=en IMPORTANT NOTE: All information presented herewith is provided on an "As Is" basis, without warranty or the implication thereof. Neither the Quantum Owners Club nor the individuals associated with the Quantum Owners Club or in the preparation of the above information shall have any liability to any person or entity with respect to liability, loss, or damage caused or alleged to be caused directly or indirectly by the instructions contained within this or related message(s). --- You received this message because you are subscribed to the Google Groups "Quantum Owners Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to quantumowners+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/quantumowners/0AC5CD85ABF849ECA1D206FF4C1CEBAA%40JimQuad.
