I have a question below which I hope someone will kindly answer to help me out with my car, but I am making a dedicated thread for this because it took me quite a while of searching and reading up to make sense of all this, so it will be here for reference for anyone who needs it in the future.
There are a handful of "coolant temperature sensors" and locations and it's not immediately clear what they each do. Here's what I can tell after doing a lot of research, at least for my '89. Please don't take any of this as gospel and read the additional comments for corrections or more information. I think there may even be another one or two that I'm not mentioning, maybe to do with the AC?
This blue two pin connector is on the right of the thermostat housing (right means right of the car) and controls the aux fan. PN 0085424517.
This black one pin connector is on the left of the thermostat housing and is for the gauge on the dash and apparently nothing else. PN 0055421017.
Here's where things get confusing. This black four pin connector is in the back near the firewall behind the left cylinder head on earlier W126 cars but up front between the idle control valve and cold start valve on later ones. This sensor sends information to the ignition and fuel systems and is a common issue for starting issues, high idle, rough idle, etc. PN 0085423217
And here's where it gets more confusing, for me at least. My car is a 1989 560SEL but it doesn't have that black four pin sensor, it has this green two pin one. It is in the same place as the one above. Can someone please advise on the rule for whether a car will have this one or the black one, and what the difference is? Many parts places I've checked don't even seem to carry this one, or they do but you have to seek it out specifically. PN 0065427717.
So on to my question. The test procedure, which I have attached for those who need it, deals with the four pin connector. It does say that "the resistances of the characteristics are identical to the two-pin temperature sensor." Are they referring to the green one, I guess? If so, I do believe that my sensor is actually bad. Please observe my findings.
~20 degrees C, my sensor reads 3.47k ohms, target is 2.5k
~70 degrees C, my sensor reads 730 ohms, target is 435
~80 degrees C, my sensor reads 620 ohms, target is 325
*IF* the readings on my green two prong sensor should match these targets in the manual, it's pretty clear that they're badly off, yes? Does anyone know that for certain? I am having a rough idle condition. Are the readings bad enough to cause that? The only thing worth noting is that my only frame of reference is the temperature gauge on the dash, which I'm just assuming is pretty accurate.
The green sensor is quite a bit more expensive than the black one. Lucky me.
Thanks so much!
There are a handful of "coolant temperature sensors" and locations and it's not immediately clear what they each do. Here's what I can tell after doing a lot of research, at least for my '89. Please don't take any of this as gospel and read the additional comments for corrections or more information. I think there may even be another one or two that I'm not mentioning, maybe to do with the AC?
This blue two pin connector is on the right of the thermostat housing (right means right of the car) and controls the aux fan. PN 0085424517.
This black one pin connector is on the left of the thermostat housing and is for the gauge on the dash and apparently nothing else. PN 0055421017.
Here's where things get confusing. This black four pin connector is in the back near the firewall behind the left cylinder head on earlier W126 cars but up front between the idle control valve and cold start valve on later ones. This sensor sends information to the ignition and fuel systems and is a common issue for starting issues, high idle, rough idle, etc. PN 0085423217
And here's where it gets more confusing, for me at least. My car is a 1989 560SEL but it doesn't have that black four pin sensor, it has this green two pin one. It is in the same place as the one above. Can someone please advise on the rule for whether a car will have this one or the black one, and what the difference is? Many parts places I've checked don't even seem to carry this one, or they do but you have to seek it out specifically. PN 0065427717.
So on to my question. The test procedure, which I have attached for those who need it, deals with the four pin connector. It does say that "the resistances of the characteristics are identical to the two-pin temperature sensor." Are they referring to the green one, I guess? If so, I do believe that my sensor is actually bad. Please observe my findings.
~20 degrees C, my sensor reads 3.47k ohms, target is 2.5k
~70 degrees C, my sensor reads 730 ohms, target is 435
~80 degrees C, my sensor reads 620 ohms, target is 325
*IF* the readings on my green two prong sensor should match these targets in the manual, it's pretty clear that they're badly off, yes? Does anyone know that for certain? I am having a rough idle condition. Are the readings bad enough to cause that? The only thing worth noting is that my only frame of reference is the temperature gauge on the dash, which I'm just assuming is pretty accurate.
The green sensor is quite a bit more expensive than the black one. Lucky me.
Thanks so much!