I’ve got what is probably an odd question. I’ve got a 1993 Mercedes that is no longer recognizing the steering angle sensor. I can buy a new one for about $350 or I can take apart the old one and see if I can fix it myself! So, I took it apart and found a bad resistor however I’m having a hard time identifying it. It is super tiny but I took a few pictures of it and I’m hoping that if I upload it here someone who is much smarter than I am can identify what exactly I need to buy. Initially, I thought the bands were Red, Red, Black, Black, Brown and I ordered a 220 ohm 1w ±1% resistor but the more I look at it I’m wondering if those two bands are green and not black but that would make it a 22.5m ohm resistor and those seem to be very difficult to find. And then also, I’m wondering if the brown band I’m seeing is significant at all! Arg! Attached are two pictures of the resistor. Any help would be appreciated!
Based on the first photo, I’d guess its brown black black red red (10K 2%) because 220 1% is not an IEC E96 value. Back in the 1960s through the 90s it was rare for me to see a non-E96 value 1% resistor. For some reason non-E96 value 1% resistors are more prevalent now.
The E96 standard value for that range of resistance is 221.
225 is also not a value in any of IEC ranges so green instead of black also seems unlikely.
Ok. Awesome! That makes way more sense. Thank you!
So, how do you know how many watts it should be rated for?
I looked around digi-key and this is what I found that looks similar: https://www.digikey.com/en/products/detail/vishay-beyschlag-draloric-bc-components/SMM02040C1002FB300/7064889
I can’t find anything that is 2%. Maybe that last red band is actually brown? I kinda doubt it but I’m not sure that 1% vs 2% is even that significant in this case because I’m not sure what it means. What are your thoughts?
It’s very difficult to determine the power rating of a resistor based on it’s size. Normally you’d read it from the schematic which would also give the other specifications for the component (e.g. tolerance, temperature coefficient, material). When the schematic is not available and I don’t know the operating parameters of that section of the circuit, I just buy the the highest power rating that will physically fit in the location (higher rating substitution is virtually always OK). Given the technology changes since that device was made, the modern power rating equivalent is most likely smaller, and in no case would be significantly larger.
Per the data sheet, the part you linked is 3.6mm long and 1.4mm diameter. Vishay Beyschlag/Draloric/BC Components has two other physical sizes one smaller, 2.2X1.1, and one larger, 5.8X2.2. They have a range of power ratings up to 1.0 W.
2% resistors are no longer common because technology changes over the last 50 years have led to manufacturing costs being very close to, or the same, as for 1% resistors.
Hi Jared6600,
So, as Paul states, going with a higher power rating is always acceptable, as that is just the maximum power it can handle without being damaged. Conversely, with tolerance (a percentage rating), that is how close to the stated value the resistor is guaranteed to be (under standard testing conditions). Therefore, a 1% tolerance will always be acceptable to replace a 2% tolerance, since it is guaranteed to be closer to the stated value than a 2% part.
On a related note, looking at your board image, it looks like you may have a bad capacitor there, too. Can’t say for sure, but I would check that out as well.
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Perfect! Thanks for all the info from both of you! This is all super helpful for me. I’ll try to order one today and also test that capacitor too. I’m not sure how to get to it though since it looks like it is surface mount and doesn’t go through the two layer board. I’m beginning to think this may be more trouble than it is worth… I know don’t give up so easily!
Jared;
When I read the color code of red, red, black, black, brown I get 220ohms. The highest wattage that we list for this resistance is one watt. The Vishay Beyschlag/Draloric/BC Components part number is SMM02070C2200FBP00, The Digi-Key part number is 749-1147-1-ND. For the web link click here
The technical reference number is T4196695
Thank you and that’s what I was thinking but that goes against Paul’s thought that:
So, I’m thinking of buying both but I’m not sure which one would be the least risky to try first.
The higher resistance value is always safest to try because it limits the circuit current the most.
So try a 10K, and if it doesn’t work, try a 220.
If it still doesn’t work, IME very likely, you’ll need to figure out what bad component caused the resistor to act as a fuse. If further trouble shooting is needed, I’d first check high power transistors or integrated circuits that connect to that resistor.
Excellent! I’ve ordered 3 of each, just in case, and we will see what happens. Thanks again everyone for all your help and support!
