3 pin coolant temperature sensor questions - Peach Parts

3 pin coolant temperature sensor questions I was looking through an online retailer parts listings for a coolant temperature sensor and I found this 3 pin sensor I've never seen (was looking at a 300E):

Part number: 006 545 42 24


I tried looking in the manuals, but I can't find information on this sensor. Does this one sensor serve the purpose of the blue (aux fan switch) AND the single pin (dash gauge) sensors?

Part number: 008 542 45 17


Part number: 005 542 10 17




I'm trying to find a way to get an additional device reading the engine temperatures without throwing off the readings on the existing thermistors. If I can combine the blue 2 pin and black 1 pin sensors into a single sensor, this frees up a port at my water pump housing that I can use to install another sensor for a completely separate device to read from.

Last edited by John; 06-06- at 05:22 AM. You may be confusing thermoswitches and sensors. The three pin device is a thermoswitch, the two paths are either open or closed, depending on temperature. The black one pin device is a sensor, it contains a thermistor which has variable resistance based on temperature. I may be wrong, but I believe the two pin device in your photos is also a thermistor, which supplies a temperature reading to the climate control unit, which in turn controls the fan.

On those cars where the red switch is used, it serves the purpose of completing two circuits. The first circuit will close when engine temperature reaches about 100C. It engages the electric fan at high speed, bypassing the resistor. The second circuit engages at around 105C, and turns off the A/C compressor. There are a couple of versions of this switch, which engage at different ranges.

If you're looking to add a device, there are a series of 22mm bungs on the left side of the head. A couple of them are probably in use, either for sensors or for heater return water. Remove one of the unused plugs, and you can install a 22mm fan switch from a VW, Jaguar, or Porsche. Mercedes uses 22mm to 16mm adapters to install sensors in these bungs, that's another option. John you look across the top of the block you should see an extra threaded brass plug you can remove to fit the new sensor in to. I use it to bleed the coolant system after a change And the the first sensor in pic is the electric fan clutch
Second is a coolant sensor ACC
Third is just a coolant sensor . Quote: Originally Posted by Mxfrank You may be confusing thermoswitches and sensors. The three pin device is a thermoswitch, the two paths are either open or closed, depending on temperature. The black one pin device is a sensor, it contains a thermistor which has variable resistance based on temperature. I may be wrong, but I believe the two pin device in your photos is also a thermistor, which supplies a temperature reading to the climate control unit, which in turn controls the fan.

On those cars where the red switch is used, it serves the purpose of completing two circuits. The first circuit will close when engine temperature reaches about 100C. It engages the electric fan at high speed, bypassing the resistor. The second circuit engages at around 105C, and turns off the A/C compressor. There are a couple of versions of this switch, which engage at different ranges. I understand that the blue 2 pin sensor I showed is a thermoswitch. It turns the aux fans at 130C. So you are saying that the red sensor is a thermoswitch for 2 separate circuits then. This doesn't fit the criteria for what I'm trying to do then.

Quote: Originally Posted by optimusprime John you look across the top of the block you should see an extra threaded brass plug you can remove to fit the new sensor in to. I use it to bleed the coolant system after a change And the the first sensor in pic is the electric fan clutch
Second is a coolant sensor ACC
Third is just a coolant sensor . The engine I'm working with on this is the CIS M104. It doesn't share the same luxury as the M103 with spare plugs to remove.



I was hoping to consolidate the blue 2 pin and black single pin sensors into 1 hole with the red sensor, leaving me with a spare hole to add an additional sensor for something else. Attached Thumbnails I searched on this forum for "3 pin coolant temperature sensor" and found this post: 190E 2.3 Temp/Fan Switch/Sensor Questions

Quote: Originally Posted by BenzEnthusiast I know that the black top 3 pin switch controls the clutch fan with 2 of the pins on it and the 3rd pin is for the temperature gauge. I know that it's for the temp. gauge because when I unplugged it the needle on the gauge drops to the bottom. But then this poster says something else: 603 coolant temperature sensor location

Quote: Originally Posted by kelley312c Just checked the wiring diagram and the three pronged sensor goes to the aux fan and the compressor, not to the temp gauge. While I was there I tried reading resistance from the two pins of the sensor and got nothing...does that mean my sensor is shot? This makes sense bc when my aux fan is engaged, it is only ever engaged on high, never on low... Another confused poster: Runs on 3 cylinders(w124).

Mbdoc: Temp Gauge - 190E

Quote: Originally Posted by mbdoc The -93 2.3 uses what looks like an aux fan switch on earlier cars.

It is a 3 pole black sensor in the head,

the single pole is for the temp gauge Maybe I'll just buy the sensor and try it out, it's not that expensive. I can't seem to find testing procedures for a 3 pin sensor in the manuals, only 2 pin and 4 pin sensors. Last edited by John; 06-06- at 06:38 AM.

ok so i watched this video about the temp sensor that controls the gauge on the instrument cluster: https://www.youtube.com/watch?v=gHlsDU-crzU

i found the sensor and there is no wire going to it (explaining why my temperature gauge on the cluster doesnt work). i bought a replacement from autozone but it was the wrong sensor(my mistake), probably the one that goes on the front of the engine(19mm). This one is supposed to be a 12mm. where is the wire that connects to this sensor supposed to come from? Is it the one in the picture right next to the sensor?? What kind of connector should I be looking for?? I can’t find a part with a similar connector attached to the brass. any help or confirmation is appreciated.

You have a SENDER and a SENSOR

The one at the rear is just a sender and personally I think it's useless. It tells the needle on your gauge what way to move.

The sensor is at the front of the engine where your fuel rail crosses over. This communicates with the onboard computer to tell it what your actual coolant temperature is. This information is directly related to how your vehicle runs IE open loop, closed loop, etc.

If you wish to monitor your actual temperatures, just run a monitoring tool via OBD as it pulls the information your onboard computer receives.

so im reading that a 02 tacoma uses the protocol. ultragauge is about 90$ and there are hardly any cheaper ones on Amazon that are compatible with the protocol. i could use a simple scanner while the engine was running probably, but that doesnt seem practical while driving. the ultragauge or scangauge would be nice though. i still think connecting my cluster to the sender would be a good idea (and cheaper) until im ready to spend 90$+. ive looked at a repair manual with a wiring diagram but i cant make sense of it. not enough brain cells left. can anyone with a working temperature gauge get a pic of their 3.4 engine from the same angle so i can confirm where the hell the wire is that i should be looking for??

ok even in that thread, and another thread ive found, the sender has a single pin coming out of it. mine has a gray connector on it. but it seems the white connector in my picture is infact the connector that controls the gauge needle. so i need a sensor with the blade connector coming out of it?? kwikvette's suggestion might be the best route actually if that gauge isnt an accurate indicator anyway.. just dont like to have things on my cluster not working might just bite the bullet and get a scangauge

respect to all you guys who dig up old threads for us dumb folk. half the time i dont know what words to use in the search bar to find what i need. you're doing god's work..

i ordered a genuine toyota sensor on ebay and i will look into the ultragauge or scangauge soon for more accurate readings. my guess is the previous owner ordered the wrong sender and put it in anyway. thanks guys

It looks like the wire was pulled off your temperature gauge sending unit which broke the plastic.

Looking straight down is there not a spade connector on top of the sending unit?

That sending unit just has a spade connector in top that at one time that plastic piece on top was part of the harness In my the wire is Yellow /red stripe The sender grounds into the engine.

That plug on the sending unit tells me we are dealing with the 4 cylinder engine.

sorry i double posted but i suspect the previous owner bought the sending unit for a 4cyl engine and when they found out it didnt fit, just left it unplugged. the correct part should have a spade connector that plugs into that white connector im pretty sure.