Coolant sensor identification
 

Hi Guys

Anyone can help me identify the 3 coolant sensor on a 190E 2.6 1991.

On the left side of the head there is one 4 pins in the far back near the firewall. This one should used 2 pins for the injection and 2 pins for the ignition. Right or wrong???

The second sensor are just a 1 pin sensor must me for the aux fan. Right or wrong???

The third one are just few inch apart from the second one and its blue with 2 pins. What is it for???

My car suffer from SSS( Sudden Stalling Syndrome) and I suspect the third coolant sensor to be the gremlins because it do not follow the NTC(negative temperature coefficient) graph for coolant sensor. Should this sensor follow the NTC graph or it should not???

Max

The two pin coolant sensor is for the engine management system. It is read to determine ignition advance and I can't remember the other parameter that is set based on its input.

Hope this helps,

4 pin is eng management
Single pin is temp gauge
Blue2 pin is aux fan/ac Control panel

Arthur may be correct. On my 88 300E, the Engine Management is a two pin sensor. In fact it was difficult to get the correct sensor, because other models have a four pin for engine management.

On that year chassis, there were several changes. But if you have the 4 prong, it is correct. ..here are the different ones for that year, according to serial#.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1W70PZW4N2080GHWOX&year=1991&make=MB&model=190-E-005&category=C&part=Water+Temp.+Sensor&appEngines=_any

The four pin should read the same ohms diagonally across from each other. The sesnor is actually 2 sensors in one casing and they are thermistor.
If one set of diag pins reads different that the other , the sensor is bad.
Do a search on 'OVP' relay........

Thanks guys for your help, Arthur you hit the nail right on the head.

Just for the record, if you have a 190E 2.6 1991 there should be 3 coolant sensors on the left side of your motor head.

If we start from the firewall to the front of the car:

4 pin sensor = Igniton and injection sensor
1 pin sensor= motor temp gauge in the car
2 pin sensor(blue)= aux. fan/ac

I just verify this with my test lamp to the ground, when I touch the 1 pin sensor connector the temp gauge rise to 80c and when I touch one of the prong of the 2 pin sensor connector my aux. fan start.

Now my question, the 4 pin sensor have small difference on is two circuit but I mean small.
This morning it is -10C over here if I refer to the NTC grahp for engine coolant sensor the reading should be around 8000 ohms mesure in diagonal, my sensor is in the spec., reading on one set of pin is 8400 and the reading on the other set of pin is 8450.
A difference of 50 ohms is it enough to make the car stall when I decelerate and the motor just reach around 85c????
Should I redone the test with the motor at 85C and see what will be the difference ???

Thanks again
Max

You want to test at running temps. NCT sensors usually run around 200ish ohms at running temps .. 105 difference between the 2 would be considered OK.

Check youy OVP relay...

Thanks Arthur

I will perform the test at running temp later this morning.

Did the sensor for the aux. fan should follow the NTC graph?
Mine is a way out reading at -10C, 19900 ohms between the 2 pin the graph say around 8000 ohms.

Did the 1 pin sensor for the temp gauge should have the same reading as the 4 pin sensor??
Mine is reading 3800ohms at -10C while the 4 pin sensor reading is 8000ohms.

Arthur I did ckeck the OVP(over voltage protection relay). Will you please verify the procedure I use just to make sure I didn't forget anything. I post this procedure in an early post here's the post:
http://www.peachparts.com/shopforum/showthread.php?t=177089&highlight=ovp+testing

Some day I will catch my car Gremlin an store it in the locked glove box so it wont get out.

Max

Gauge sensor is different

OHM 110 = 60C
67 = 80C
38 = 100C


As far as the others , I don't care what thery say cold , it is at runniong temps you want to make the checks...

Ok, here's the test at running temp:

Engine temp gauge at 80C

-4 pin sensor reading = 270 ohms diag 1 and 290 ohms diag 2.
-1 pin sensor reading = 64 ohms
-2 pin sensor reading = 520 ohms

-The 4 pin sensor is just a little bit out the spec. of 325 ohms at 80C and 247 ohms at 90C
-The 1 pin sensor is just in the spec. for 80C (-3ohms) at 64 ohms.
- The 2 pin sensor, I cannot find any spec in my shop manuel, what it should be??

Did the small difference between the spec for the 4 pin sensor and my reading can cause the SSS(sudden Stalling Sydrome)?

Thanks again
Max

All sensors are good.
I repeat . check /archives ...."OVP relay .."

ditto!!!!