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Well after our lengthy discussion about this tonight, i will do an experiment tomorrow.
I have an old o2 sensor in my parts drawer. It is a 4 wire design. I will ohm out the wiring, then cut one, solder or crimp and re-ohm and see what the results are.
With o2 sensors working on a 1v Ref, just the slightest change in resistance will probably effect the stoichiometric ratio.
I guess this type of repair would all be dependent on the technician and his principles for these type of repairs and situation.
If resistance is a concern, the amount of current running through the sensor would determine if it would be an issue. If current is very low, then there should be little effect on the voltage read. I’m nor sure why solder would be an issue especially where there is probably plenty of solder on whatever circuit board reads the signal.
I’ve also been taught to never solder them. I’ve never really done the research as to why not to, but I was told that the sensor needs to draw fresh air from inbetween the wire strands to work properly, and the solder keeps it from drawing air. This was back in the day when one wire sensors were all you really encountered though, for what it’s worth.
It would be interesting to see if it makes a difference though.
Quoted From Moose:
I’ve also been taught to never solder them. I’ve never really done the research as to why not to, but I was told that the sensor needs to draw fresh air from inbetween the wire strands to work properly, and the solder keeps it from drawing air. This was back in the day when one wire sensors were all you really encountered though, for what it’s worth.
It would be interesting to see if it makes a difference though.
+1 You are right.
This is the first article i found that states the above.
I’m kind of skeptical about the air being drawn bewtween the strands of wire. The strands are tightly packed and I would think that if fresh air was crucial then wouldn’t there be a vent dedigned in? I’m going to research this myself cause I am curious about this.
This is an abstract from a GM service manual that pertains to 4 wire o2 senors. I am going to keep researching also to see if i can find some visuals.
Do not repair the wiring, the connector or the terminals. Replace the oxygen sensor if the pigtail wiring, the terminals or the connector is damaged. Proper oxygen sensor operation requires an external air reference. This external air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, the connectors or the terminals results in the obstruction of the air reference and degrades the oxygen sensor performance
O2 sensors use either chrome or nickel plated wires also which is more difficult to solder than per se copper.
I also found another explanation which perfectly makes sense –
Dissimilar metals have a contact potential that varies with temperature. If the solder is between the two wires, any small temperature difference will create a voltage across the joint, hence giving a bad reading. This is called the galvanic effect and is the basis of how thermocouples are made.
I was a little skeptical at the time too, but the same person who told me never to solder O2 sensor wires was the same guy signing the paycheck, and he’d never steered me wrong any other time. I read a little bit more and there’s tons of various forum posts debating the matter, and I think the only universally agreed upon item is that oxygen sensor manufacturers tell you to crimp the connections rather than solder them. There is a lot of debate out there as to whether or not it’s possible for air to travel through the strands, why don’t they just put a vent somewhere if that’s the case, etc. Some claim that the vents become clogged with debris, grease, and other contaminants so they engineered the reference sample to travel through the wire. Again, that’s all other people’s internet research, so your mileage may vary. There’s lots of reading out there on it supporting both camps though.
The only document I could find that supports the claim that reference air is carried through the cable is here: http://apps.bosch.com.au/motorsport/dow … nlsm11.pdf Seeing as it comes from a manufacturer, I’ll lend my credence to them and continue to crimp the connections so long as it’s one of theirs. I don’t know if Denso or NTK sensors are manufactured the same, but I suspect they probably are. NTK instructions say to crimp the connections, but don’t say not to solder them like Bosch does.
Anyhow, the document contains the following 2 points:
Ok now I’m on board with you guys now. After getting clarification directly from a manufacturer of o2 sensors, who also says not to use any kind of connector spray or anti corosion agents on the connection. I had found this link below but I think the previous poster just beat me to it.
http://apps.bosch.com.au/motorsport/dow … nlsm11.pdf
Quoted From twiggy02919:
Ok now I’m on board with you guys now. After getting clarification directly from a manufacturer of o2 sensors, who also says not to use any kind of connector spray or anti corosion agents on the connection. I had found this link below but I think the previous poster just beat me to it.
http://apps.bosch.com.au/motorsport/dow … nlsm11.pdf
That’s good to know you agree seeing as you are extremely smart in the electronics department C8-)
Great info. I like to stir up a good discussion. I too am more likely to follow an O2 sensor manufacturer’s recommendations than something from Porche.
Thanks Dreamer, but this thread illustrates why just knowing electrical theory is not enough. This is why I am so glad to have you guys around with the incredible wealth of knowledge you guys possess.
I agree Twiggy. I really love this forum. Very educational at times. I have learned alot since becoming a member here.
I have heard that also the length of the wire matters as well. It should always be the same length as it left the factory,or that will also cause a bad signal.
Also I have a question.
I had a little fire accident and my o2 wire that leads to the ECM melted,so I had to cut out about 40cm of it,I need to add those 40cm in with a new wire. What wire should I use? Its a 1993 BMW e36 with M50B25 engine,witch “BOSCH” ECM if that matters. And the o2 has 4 wires.
I have heard that also the length of the wire matters as well. It should always be the same length as it left the factory,or that will also cause a bad signal.
Also I have a question.
I had a little fire accident and my o2 wire that leads to the ECM melted,so I had to cut out about 40cm of it,I need to add those 40cm in with a new wire. What wire should I use? Its a 1993 BMW e36 with M50B25 engine,witch “BOSCH” ECM if that matters. And the o2 has 4 wires.
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