Question Jim, do these ‘just’ provide load for the car side bulb monitoring or does it pull the nominal 12v down to a working voltage for the leds, which is likely to be much less on small bulbs?
Ian On Fri, 9 Jul 2021 at 12:06, mgaskin via Quantum Owners Group < quantumowners@googlegroups.com> wrote: > Thanks for that, Jim. > > > > I’d always had the vague nagging doubt that Canbus bulbs probably did > their thing via resistance, rather than electronic cleverness – and > therefore entirely negate the biggest benefit of LED bulbs. > > I shall remove resistors with impunity on all my new LED bulbs. 😊 > > > > Matthew > > > > *From:* quantumowners@googlegroups.com <quantumowners@googlegroups.com> *On > Behalf Of *Jim Hearne > *Sent:* 08 July 2021 11:32 AM > *To:* quantumowners@googlegroups.com > *Subject:* Re: [Quantum Owners] "CANBUS" LED bulbs in older cars. > > > > 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 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