The malfunction is interesting: “the cooling fan is constantly spinning.” A person turns on the ignition – does not spin, but as soon as the engine starts, here the fan starts to work.
Have you also thought about a temperature sensor? Like, is that the reason? That’s it, and in car services, where the client came for repair, they also thought so. And they confidently replaced him. And they were surprised: “Nothing has changed.” And they sent the client on a trip: “Look for the profile auto service”.
Alas, our car service is not specialized, we don’t deal with such cars, but it was a really interesting malfunction – that’s why I agreed to take this car for repair.
And regretted it. Because the “universal” scanners that “take Hyundai from TAGAZ”, this time refused to work with him. Everything doesn’t bind: one scanner refused, the second showed nonsense – summer is around, heat, and the scanner proves that the engine temperature is “minus 40 degrees”.
Then at first I was delighted, showed the client, they say, look, the problem is in the temperature sensor! To which the client sadly replied: – And I already changed this sensor … nothing has changed …
I decided to check. He threw up the old sensor, checked – everything is the same. I checked both sensors for resistance: taking into account the error, both sensors are the same – not short-circuited, the resistance is the same … miracles, and only.
I take my device: “Dial resistor”:
This is “The usual assembly of stacked resistors with 100 Ohms, 1 Kom and 10 Kom. Using this assembly you can emulate various conditions, for example, a temperature sensor, etc. like that.” See here for more details.
Using a dial-up resistor, I change the resistance in the circuit and the control unit perceives this as a temperature change: near the boiling point, the fans suddenly started working at full strength. The conclusion is: “The problem is not in the sensor”.
But there are no miracles. So, the malfunction hid somewhere deep and … close. You just need to pick up your thoughts. But without the “right scanner,” which would show the real state of affairs, one cannot do. Therefore, he told the client to drive up tomorrow. And in the evening he took out his “home” scanner, checked it and tried to find at least some data on this machine on the Internet …
I won’t praise this scanner, I can only say that Scanmatic-2 sometimes helps me out very well. Its coverage is not like that of a dealership, but, for example, it’s very, very convenient to diagnose the “SS4-II” distribution on Pajero4 on it. Even more convenient than through MUT3.
In the morning we again met with the client, connected the scanner and was delighted: wow, there is a real sea of information! I already see the real data, the real temperature and again I am convinced that the temperature sensor has nothing to do with it. I activate the fans with the scanner, I take them out at different speeds and I understand that the fan circuit is working, no relay is “stuck”, everything turns on and off.
But looking through the “date sheet” he was wary: “Why is the status of the air conditioner constantly on” on “?” I looked at the panel – “off.” I looked at the scanner display – “on.” I press the condition button – the status does not change (for convenience and out of habit, I call “climate control”).
Then I will try to “catch on the status flag.” I look at the WIRING DIAGRAM, and suddenly I see a very interesting thing: how interesting is the wiring of electrical circuits! When the driver in the car interior presses the condition button, the signal first goes to the engine compartment, then returns from there to the control unit. Why is that? But wasn’t it easier not to pull 2 meters of wire into the motor and two meters back to transmit a signal from one block to another, which are 30 centimeters from each other in the passenger compartment?
Interesting? Undoubtedly! And what is in the engine compartment? Some kind of Manufacturer’s trick? Otherwise, why pull such long wires back and forth?
I look in the motor. I find the mounting block. With interest I open, look, study. And I wonder: no tricks. Common jumper. There simply is a banal jumper through which the signal comes from the passenger compartment and goes back to the passenger compartment!
Disconnected the wire that goes to the “brains.” The fans were silent. I looked at the scanner display: the status is “on” is gone, there is no flag, the air conditioner is off.
Carefully examined the mounting block. Found “greens” and oxidation. The conclusion is simple: due to long-term operation on our roads, which are generously sprinkled with reagents, inaccurate washes of the engine compartment under high pressure, moisture has got into the mounting block: oxidation and “pick-up” of the electric potential (“plus”) to the air conditioner contact have occurred. As a result of this, the “plus” began to arrive at the control unit, and one did not have to think: “if there is a plus,” it means you must turn on the air conditioner “!
Well, change the assembly block assembly? How much does it cost? Wow, over 10 thousand. And if you make it easier and more reliable? He suggested to the client: – Let’s exclude the mounting block from the air conditioning control. Leave the factory wire, just connect it outside the mounting block.
Customer agreed. And that is a good option. Budget and reliable will be. And so I did: connected the wire outside the mounting block, securely insulated – we check?
We turn on the ignition, start the engine – the fans are silent. Turn on air conditioning – everything works as expected. And the scanner shows: “Everything works correctly!”.
So I remembered: sometimes you should not look for the logic of the Manufacturer. Sometimes he does as he sees fit or as a dream of some engineer. And to us, the diagnosticians, then to disentangle it. But looking for this fault was interesting.!
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