help to ID coolant temp sensor

[flagstaff]

would be grateful if someone could take a look at this pic

http://www.yeknom.karoo.net/P1030800.JPG

and let me know whether sensor a or b is the coolant temp sensor

thanks very much!

 

[flagstaff]

forgot to say - this is the M102 2.3l motor, pic is of upper cyl head right hand side (when looked at from front of vehicle)

 

[NormanB]

Hi

Yes I know this!

a= sensor for fan circuit (energises the viscous fan clutch) if you remove the plug and bridge the two connections in the plug with the ignition switched on, you should hear a 'clunk', if the engine is off and with a fan clutch in good condition you should now not be able to tuen the fan by hand.

b= sensor for engine temp gauge.

Does this help?

 

[flagstaff]

thanks norman - it helps ... a bit :?

so is the 'engine temp gauge' that you mention the same thing as the coolant temp sensor? or is it simply the sender for the instrument? or are these the same thing

 

[flyingtech55]

Hi NormanB

What's the thing with the two connections between the two sensors labelled 'a' and 'b'?

 

[sunil sood]

thanks norman - it helps ... a bit :?

so is the 'engine temp gauge' that you mention the same thing as the coolant temp sensor? or is it simply the sender for the instrument? or are these the same thing [/qu

sensor a has the pins on it.

2 of them act as a bridge to allow the cooling fan to cut in at a critical engine temperature.

the third single pin is a an engine tempersture sensor that links to the temp gauge.

that setup was what it was on the merc 190e-1.8 -1993

 

[flagstaff]

cheers for that sunil - so it looks like (b) is the temp sensor. to be safe, i simply ordered a new one from merc, so i figure it'll be obvious when i get a look at it!

 

[flagstaff]

flyingtech55 - the thing with the two connectors is (i believe) a vacuum connection from cyl head to gearbox. just a guess, but i would think that once the coolant gets up to a certain temp, a vacuum switch tells the gearbox not to hold the gears for as long as when the engine is cold. like i say, just a guess

 

[carl_w]

Bizarrely I have an almost identical thread running over at 190revolution.net!

So is the consensus that "a" is the sensor, which has three pins -- two for the fan and one for the gauge? If it fails, does that mean that the fan doesn't engage and you can't tell it's overheating because the gauge doesn't register? And what's "b" then, which appears to have four pins?

 

[flagstaff]

hm ... the new part from merc came today, and it's actually (a) in the picture. when i ordered, the parts guy specifically asked me "are you sure you want the coolant temp *sensor*, as opposed to the temp *sender*?" and i said yeah, it's the sensor i want. this is part (a) in the pic, and installation has cured the problem i was having - surging idle, sometimes as high as 1400rpm with engine fully warmed. i figured that if the sensor was broken, it might be telling the fuelling rig that the engine was always cold, hence the overfuelling. looks like this was right.

so part (b) in the pic must be the *sender* for the temp gauge. the haynes manual seems to confirm this (although to be honest, it's not crystal clear).

the sensor on my particular model seems to serve two functions then: one (the two-pin) being a switch for the fan, and the other (one pin) for sending information about coolant temp to the fuelling side. i say on my particular model because i know someone with an '88 230TE and on theirs, the fan switch and coolant sensor are two separate units in the cyl head.