You know what Arthur,
If you are in Ottawa, Canada, I would invite you to go out for few beer in a hot sunny weather. Just because your generosity.
And again, thanks a lot.

If I had a few beers , you would probably get a false diagnosis ..:)
..but thanks for the offer.

Hi All again,
I have replaced the ACC push button according to a mechanic and the fan is still on. I bring my car to other mechanic he told me that may be wiring problem. This guy is the guy who replaced my engine harness in Nov, 2006. He said there are 2 harnesses go into computer, he said may be the second harness having problem. I don't know what I'm going to do now. Any help?

Thanks,

Try this before changing any more parts

Pull the connector off the blue 2 wire sensor and connect a 1K ohm resistor [ just a little 1/2 watt one-Radio Shack/electronics store] across the connectors two female pins..does that stop the fan????

Do you mean that 1/2 Volts drop (not Watts) right?
I measured voltage drop when the connection is on and it's 0.445 V.
But I will go and buy resistor anyway.
Thanks,

Resistors come in wattage aside from resistance..so, I am just saying you only need a little 1/4 or 1/2 watt resistor , not a big 10 watt jobber...that is the sensor side of the cicuit and there is only miliamp draw, so it does not require a large wattage resistor.... jusy a little 1/2 watt/1K ohm resistor ... they are like .99 cents for a package of 5.
This is just for a test to take the sensor out of the circuit without tripping the default funtion of the CC unit.
The CC unit will see a cold sensor cuz you are fooling it.

I'm going to do so on the way home. I'm at the office now. I did try to short this connector... but it did not do any thing different. I guess that just the default short circuit kick in.
I will let you know as soon as I get this resistor.

Thanks,

[QUOTE=dinh_hai_tran;1536207]
. I did try to short this connector... but it did not do any thing different. I guess that just the default short circuit kick in.

Yes, but shorting the connector tells the CC that the cut-in resistance spec has been met and it then calls for fan.. High fan cuts in about 285 ohms.
The blue sensor is a Negative Coefficient Thermistor, simply meaning that as the coolant temp increases, the ohms decrease..so jumpering it just tells the CC you have past the cut-in spec...BUT, by using a 1K resistor, you are assured of complete circuit without reaching the 285 ohm cut-in fan trigger..get it??
It's best to just do the test and report the finding

Hi Arthur,
I did exactly as you said, resistor 1k 1/4 watts connect to the wire. The fan did not stop. Here is another hint. By accident, when I start the car for checking faulty code by pressing + holding REST key on ACC control panel, the fan stops and AC is ON. Of course, this is not a permanent solution but at least I can get AC on. By doing this, I have to close look at the coolant temp to be sure that the car is not over heated since AC ON fan OFF.
Does this suggest you something wrong?

Thanks,

Kinda strange. I am thinking that the harness they changed has got to be the problem.

I do not have the 140 schematic... I do have the 124 of same vintage..but the 140 uses a few different speeds and fan controls, so I don't like using the wrong one.
However, I did do some testing on 124 sensor/thermistor circuit on a live car w/working fan circuit . What I found that does not match up with your test is that the thermistor circuit is a 5V circuit, not 12v as your voltage drop test showed.
On my test, if I unplug the sensor , I get 5V at the feed side and trace on the return wire. This does not match up w/your findings , so this is something to consider...is the wire harnes they changed incorrect or does the 140 use a 12v feed to the thermistor ?? [ which I highly doubt]..I do not know the answer to that question, but I consider the answer to have something to do with the diagnosis to that point in the fan circuit.
I also mentioned to you earlier that if you could get to the fuse that feeds the coil side of the fan relay and pull it.....if that stops the fan, you know the sensor side of the circuit is at fault, rather than the fan load circuit..[ which would be a different /high amp fuse]..in other words , is the primary side of the relay being constant fed HOT or is the contact [ load side ] of the relay somehow picking up 12v somewhere ? [ you mentioned fan stops when relay is pulled , but pulling the relay disconnects both the relay coil circuit and contact circuit]. I would expect the fan to stop when you pull that fuse.. Check your fuse map for aux fan relay and try it...this would be what your guy is talking about when he mentions relay is alway HOT, but it would determine which side of relay is hot [ he probably also already knows that]
Tricky diagnosis and b/c of your complaint coming up when they did the wiring change, I think that needs some further looking at. Could 12v be at the thermistor due to wrong harness?? very well may be..
The 1K resistor test was just to satisfy the trigger default circuit of the CC, but if you show 12v there and it should be a 5v circuit, who knows how the CC sees that as..I just don't know the answer to either of those questions .

Thanks Arthur,
I do have a friend who has the same car. I will test his AC temp. sensor for the voltage difference, this is very easy test. For the fuse side, not the Aux. relay, I did unplug this fuse and it make no difference, I mean the fan is still ON. I will post here as what I find out the voltage difference of my friend's car.

Thanks,

Following fuse descriptions might be of help:

Engine compartment fuse box

Fuse 2 - 30 amp main supply to auxilary fan relay contacts
Fuse 18 - 15 amp air conditioning aux coolant pump control relay module
Fuse 20 - 10 amp automatic climate control base module (might power relay coils)

Rear compartment (boot)

Fuse 1 - 15 amp rear climate control

hopeit helps

I would like to thank all of you, especially to Arthur with his knownledge and generosity. Without him, I could not find something wrong with the car (I believe that many mechanics don't know either).
The actual problem is the : HARNESS. I checked the cable from my friend's car, the actual voltage difference of the AC temp sensor cable is 5 volts as Arthur stated (as opposed to mine 12V). I looked at part number of the two harnesses and they are the same 000 545 4881. From my friend's car, I used Ohm meter to link the wire from the sensor to other end (computer), one goes to pin 6 and the other goes to pin 7 (wire color is brown and blue). And my wires go to pin number 31 and 5 (brown and red). I also measure voltage difference between between pin 6 and 7 of my ECU (computer) and It is 5 Volts. So the conclusion (hard to believe but it's true) is that the Harness wiring is wrong from MB or whatever supply part to MB.

Again, thank you very much,

Cool..

Thanks for the outcome reply..it was starting to bother me too. We do like to see a diagnostic conclusion/ remedy.