Hiya, could anyone tell me what voltage the 3.3 ohm resistor for the airbag plug should be please?
I have 100 that are 1/4 of a watt, would that be ok?
thanks.
Tom - can you define what you are doing, and what you need the resistor for? I’ve checked the manual for airbag, and there’s no 3.3 ohm resistor in it, so I’m puzzled.
Sounds like he’s removing the airbag and want’s to simulate the load to turn out the warning light…insurance, insurance and insurance
My thoughts too - and there’s the MOT to consider.
Sorry, should have been more specific, I want to fit a better wheel and you need to put a resistor across the plug to put the airbag light out. I know it’s 3.3ohms but these things come in different voltages.
Soooo, back to the original question,…
Well, it’s a 12V system, obviously - but you’re asking about the power rating, I believe?
I=V/R=12/3.3=~4A (max)
W=I*V=48W (max)
I don’t understand that, sorry. I know it’s a 12v system but I don’t know if the voltage on the resistor in this particulay instance is important. I only know, as a layman the I need a 3.3 ohm resistor to bridge the connections on the airbag plug. Do I need a particular resistor for that? What would I ask for in Maplins?
Thanks.
It really depends on the circuit and in particular the current that flows through that resistor. Resistors have different power ratings (wattages) not voltage ratings.
The theoretical maximum that will be in that resistor is 48W, if it is simply connected from live to ground…However, it won’t be. I expect you’ll be fine with a simple 1W resistor, but probably not with a 1/4W.
Expect Maplin to sell you a bag of many hundreds that you don’t need to get the one you do. I might have a suitable one in my box o bits, I’ll have a look.
No, sorry, I have about everything but…
If you say you have some 1/4W ones already, you can try one. If it works it works, if not you’ll hear a pop, but it shouldn’t do any damage.
If you have some 1/4W 10ohm resistors as well, then you can connect 3 in parallel to get a 3/4W 3.3ohm. Or you can find a 1W 3.3ohm from Maplin or ebay.
Hi Tom
Resistors are rated in watts not volts. Unfortunately to work out the wattage required we need to know what the rest of the circuit is, and that is completely unknown
The value of 3.3 Ohms seems to me to be very low, are you sure it’s not 3.3 K Ohms you want.
R-b
Thinking about it, I suspect it needs to be there to simulate the coil of the solenoid that sets off the airbag, in which case 3.3ohm seems about right. In which case…it is probably part of a voltage divider or a wheatstone bridge and therefore probably only getting signal current and therefore probably a 1/4W will do.
Jon
You are probably right, the only problem with a resistor as a subsitute for the coil is that if and when the air bag system goes off for real the ¼ watt resistor gets the full 12 volts as in your calculation above and maybe burns out or catches fire depending how long the current is on for.
R-b
Somehwat puzzled here. Is the resistor to remain permanently in circuit with the new steering wheel fitted, or a temporary measure while the wheel is changed? If temporary, once the battery is disconnected and the capacitors have discharged there will be no current. If permanent the location may give you some indication as to the wattage, they increase in physical size as the wattage increases. If the wattage is greater than say 15-20W I would have thought heat would be a factor and some form of heat sink would be needed. Perhaps the manufacturer of the steering wheel could supply the information.
Regards Geoff Peace.
The OP has already statd what he wants to do - remove the airbag wheel fitted and replace it with a non-airbag wheel, there’s no puzzle here, but there is sufficient concern about removing a safety item for a non safety one. I may be an old Fogie, but I don’t want to pick up a newspaper one day and read that so and so was killed (or severely injured) in an accident that may or may not be a fault of the driver, but what killed or injured him was on account of removing an airbag for the sake of aesthetics, which means the vehicle was illegal and the insurance won’t pay out either because of the removal of said safety device.
Warning bells have already been rung! This isn’t a cat issue, it’s far more important than that. If someone can prove me wrong, then I shall retract this statement and put my coat on - - - -
Yes quite a few legal and moral issues here I think. What about insurance? What about the MOT? What if you sell the car and don’t make a formal disclosure? How can they test if you have working airbags anyway (not just the light)? Would a 22 year old airbag deploy safely, or not go off at all, or split and smack you in the face? Do they have a replacement date? etc, etc. Best not to mess would be my advice.
Oh yes, it’ll go pop and the warning light will come back on, but it should be fine, I blow those things up all the time. 
As for safety I can’t say much except that I believe that people should be allowed to take risks with themselves if they wish. But obviously you need to tell your insurance about any modifications at all. They will use it as an excuse to not pay out if you don’t.
Phew!
Thanks for all the input.
Several people on here have done this mod, some of them have imported a kit from the usa that has a boss and a made up resistor to fool the airbag light. I rather hoped one of them would have seen this post and chirped in.
I have obviously looked into insurance, legalities and MOT scenarios as have many others. The wheel fitted as standard makes the car feel as though the steering wheel is attached to two vats of blancmange, there is nothing wrong with the car at all but compared to my Mk1 it just feels dead + it’s too big.
Anyway this is getting too silly so I’ll forgo all the doom & gloom, I’m 65 and used to rally an old Celica many years ago so I’m just a very bored retired old git who is still mentally 20 yrs old :lol:
I’ll sell this as planned and carry on ragging my mk1 which has no airbags and feels alive in your hands.
Many thanks.
Tom, I sympathise and didn’t mean to criticize, just to raise a few questions about what is becoming a silly piece of legislation. No doubt airbags were introduced to help stop injuries, not many car makers fit expensive kit voluntarily. However we are now 20 years down the line in this country, and 30+ in the US, but there doesn’t seem to be a sensible clarification about older cars.
For example, if your Mk2 airbag goes off for any reason I don’t think you can get a new one from Mazda. If they are out out date and need replacing (some manufacturers give a date) you may not get one or find they are economically too expensive. If you disable or remove it then sell the car to an unsuspecting new owner who then injures themselves would they have a claim against you?
My thoughts are that we’re now reaching a point where there needs to be either; 1) onus on the vehicle manufacturer to supply continuing product support at a price commensurate with the value and use of the vehicle (not likely) or 2) a time limit placed on a new airbag car after which the airbag laws including lights on the dash etc no longer apply, say, 10 years. So anyone buying, driving, or insuring a 10 year old car would know where they stood.
Similar law applies to seat belts in old cars. There is already an acceptance of classic cars and they are excused road tax. A time scale is applied for MOT testing etc. It would be very easy to implement. Cars after this age become relatively few so it wouldn’t affect attempts at improving road safety. That just leaves the hidden agenda of the car industry and government in making vehicles obsolete so we have to buy new ones.
Totally agree Rich, it’s really a large can of worms when you take all that into account.
I think I’ll reduce my price and sell this on instead, I have found another Mk1 at a silly price that I fancy getting.
Thanks for all the help.