Cooling fan control relay
Every internal combustion engine must have an efficient cooling system. Without which the motor will overheat and all of its moving parts could fail. Modern cars are equipped with a cooling system in which the coolant circulates. Circulation is by means of a special pump. Any coolant starts to boil when heated up for a long time. To prevent this there is a radiator in the cooling system. The engine cooling radiator consists of many thin tubes, to which are attached special lamellas, to increase the cooling area. When the car is moving, air passes through the lamellae of the radiator and cools the metal, thereby reducing the temperature of the coolant. But at low speeds or when standing in a traffic jam, the radiator is not able to withstand engine overheating by itself. In such a situation, an electric fan comes to the rescue and activates automatically at a certain coolant temperature. If the cooling fan fails, the engine will overheat. Below we will consider why the radiator fan does not turn on, as well as possible causes and malfunctions that lead to this and methods for their elimination.
WHERE THE FAN RELAY IS LOCATED
It’s housed in an auxiliary unit.
Relays and fuses may be in a different order. So you need to be guided by the color of the wires. The main relay is always located at the bottom. Find the relay from which a pink thin wire with a black stripe extends. It comes from the main relay through pin 85. Be careful! Don’t mix it up with the red thin wire, which also has a black stripe and runs out of the controller. And look for the white thick wire with the black stripe (pin 87). This is where the cooling fan relay is located. There’s always a fuse next to it. It is part of the circuit.
Repair of automatic fan control unit (ACU) with your hands
If the conditioner or climate-control does not start. there are two frequent reasons: either low of freon or defective fan control unit (BCU).
Looks like my OBU is busted after all. On the connector of the radiator, I short-circuit pins 1-2, the fan turns on speed 1. I short-circuit 2 or 3. nothing, even the relay in the ECU does not click.
Most likely there is a loose solder in the controller. Disassembly is simple: take out and unscrew all the fuses, unscrew the sealant from below and carefully take off the lid not to break the pawls.
Started to figure out where I had the second speed. Disassembled one of the control units, here it is, as seen from the board side. No outright cold soldering anywhere. I screwed the fuses in and put them back in place for later testing on the car.
This is on one side. Left to right, relays: 1. switch on the 2nd fan speed, 2. switch on the 3rd fan speed, 3. switch on the additional coolant pump.
This is a 180 degree turn. On the left side of the AC clutch solenoid relay.
During the on-site test it turned out that the second speed is not turned on because of the plus on the other leg of the relay, which should be the “minus”, when the signal to turn it on. plus on the other leg, there is also a plus. A quick checkup showed that “negative” leg is on minus through a reconnected diode. Yeah, so, there must be a key somewhere.
Took it home, had a good look, and this is the story of how the second speed comes on:
So, this whole thing is designed in such a way, that the second speed can by no means come on when the ignition is off. Or rather, that it is switched off at switching off ignition, if the temperature is 95-100 degrees.
The elements are numbered loosely only for this picture, it works like this: when you turn on the ignition through fuse 4 (in my case, in the very first diagram above, it is marked as 3) from bus 15 through connector T10 of the BUV through decoupling diode VD1 voltage on-board network through dividers R1R2 and R3R4 (the latter sets offset voltage 0.76V) gets to the base of transistor Q1, which opens, and when the plus from the sensor on the heatsink from its contact 3 to contact the BUV T10/7 is activated second speed.
You can use a “crutch”. solder a jumper to the diode VD2, then the second speed will not turn off after turning off the ignition until the coolant cools to the threshold of operation. But it’s a last resort if you can’t find the root cause. Plugged it in this morning, no voltage at T10/9 when I turned the ignition on.
I looked at fuse number 14 and it was burnt. Damn, it’s also responsible for both the rocker panel light and the reversing light. 10 amps. I’ve had it burned out before. I put in a 15A fuse. I checked and there’s voltage. Plugged in another fuse, which is still in place. Drove to work. second speed doesn’t work.
Took the fuse out. it’s not a bastard, it’s burnt!
Considering it’s burned out before and with a different control unit, there’s a good chance it’s not the control unit. It’s more likely that there’s a short somewhere, most likely in the rocker arm.к. It doesn’t burn out right away. I mean, something moves, it must have shorted out, and bang! Now I’m gonna have to find that damn short. One of the nastiest stories is when it’s floating.
There’s another problem. When the coolant temperature gets 90 degrees Celsius, the contacts of solenoid relay started rattling (of course, when the air conditioner is on). The clutch is “clutching”. switching on and off with frequency of about 2 Hz. Very unpleasant effect.
The only reason I can think of is that the thermocouple in F165 is dead. Well, if it’s the diode. Because the second possible reason is the contacts in the pressure sensor are screwed. And replacing it is already recharging the system. But let’s hope for the best.
I’m afraid to jinx it, but it seems that the short circuit was found rather easily. a light bulb for backlighting of the rocker panel, damned if it isn’t. The last time was at a demolition in Pushkino, took one in stock, but put it all was not able to. Now I have to.
Drawn more or less BUV completely, with passive ratings, though types of diodes are not completely clear, but something like KD521, and one more powerful, can not read, on the back of the board is uncomfortable.
But it’s not a big deal. One diode is not clear at all. It looks like a regulator, but costs exactly like a diode. In the picture it is circled in red. I also could not find a color code to identify it. White and green stripes.
- Tipped that it is most likely a smd diode. Housing and type MELF DO213AB
- The other two circles are clear, on the left side is a BAS21 diode (in the blue circle, marking JSp, housing SOT23), in the pink one is a NPN transistor also in SOT23, I also found it, I don’t remember now, it is written in the paper.
The circuit design is pretty clever. I mean, I was getting a kick out of it.
The design of the system and the principle of switching of the fans
Also in engine cooling is used heater fan of Chevrolet Niva. Part of the system has little effect on temperature control, but in an emergency, it can affect the operation of the motor.
It is located in an additional block.
Relays and fuses may have a different order. So you have to look at the color of the wires. The main relay is always placed on the bottom. Find the relay with the thin pink wire and black stripe. It comes from the main relay on pin 85. Be careful! Don’t get confused with the red thin wire, which also has a black stripe and extends from the controller. And find white thick wire with black stripe (pin 87). This is where the cooling fan relay is located. There is always a fuse located next to it. It is part of the circuit.
By eliminating the need for the belt-driven fan to turn continuously, the engine warm-up time is shortened. The electric actuator which consists of the motor, relay, overload switch and battery, allows the fan to run only when the engine temperature exceeds the optimum value. This approach has made the internal combustion engine cooling system more efficient. Turning on the fan periodically has reduced fuel consumption, because the warm-up time of the motor is shorter and there is no loss of power to the constant rotation of the blades.
Fan control unit scheme VAG 357 919 506
The block of fan control VAG number: 357 919 506 was installed on: Volkswagen Passat B4 / Volkswagen Passat B4 (3A2) 1994. 1997 Volkswagen Passat Variant B4 / Volkswagen Passat Variant B4 (3A5) 1994. 1997 Volkswagen Golf 3 / Volkswagen Golf 3 (1H1, 1H5) 1992. 1998 Volkswagen Vento / Volkswagen Vento (1H2) 1992. 1998 Volkswagen Polo 3 / Volkswagen Polo 3 (6N1) 1995. 2000 Volkswagen Corrado (509) 1988. 1995
If air conditioner or climate-control does not start. there are two frequent reasons: either low freon, or defective fan control unit (BCU).
Looks like my OBD is busted after all. I short circuit pins 1-2 on the connector of radiator, the fan turns on at 1st speed. By shorting pins 2-3. nothing, even the relay on the ECU does not click. Most likely a loose solder in the CUI. Dismantle the block is simple: take out and unscrew all the fuses, unscrew the sealant from below along the perimeter and carefully, so as not to break the tabs, remove the lid. The board is all there like you can see.
Found the schematic of connection of the climatronic for my car, and with it the control unit is painted
There is a shoosh on the schematic one. thermoswitch S516 in real life is normally closed.
Also got the pinout of the remote control for a Volkswagen Golf 3 / Vento, but ours is the same for the Volkswagen Passat B4.
Started to figure out where my second speed went. Disassembled one of the control units, here it is, the view from the board. There is no outright cold soldering anywhere. Screwed in the fuses and put them back in for later testing in the car.
This is from one side. From left to right, relays: 1. 2nd fan speed on, 2. 3rd fan speed on, 3. auxiliary coolant pump on.
It is 180 degrees turned. On the left side of the air conditioner solenoid clutch relay.
During on-site testing, it turned out that the second does not turn on due to the fact that the relay’s leg, which should be a “minus”, when the signal to turn on. plus on the other leg, there is also a plus. A quick exam showed that “minus” leg sits on the minus side of the diode. Yeah, so there must be a key somewhere.
I took it home, had a good look at it, and the result was this story of how the second speed comes on:
That is, all this stuff is tortured solely so that the second speed can not turn on at all when the ignition is off. Or rather, to make it turn off when the ignition is turned off if the temperature is 95-100 degrees.
Citroen Relay Cooling Fan Control Circuit Open Fixed
The elements are numbered loosely only for this picture, it works like this: at switching on ignition through the fuse 4 (at me, in the very first diagram above it is designated as 3) from bus 15 through contact T10 of the BUV connector through isolating diode VD1 voltage on-board network through dividers R1R2 and R3R4 (the last sets offset voltage 0,76V) gets on base of transistor Q1 which opens, and at receipt of plus from the sensor on a radiator from its contact 3 on contact BUV T10/7 second speed turns on.
You can use “crutch”. solder jumper to diode VD2, then second speed will not turn off after ignition is turned off and till cooled down to operating threshold. But this is a last resort if the root cause can’t be found. Plugged it in this morning and when I turned the ignition on, there was no voltage at the terminal T10/9. I looked at fuse number 14 and it was blown. Gad, this diode is also responsible for illumination of a rocker panel and reversing lights. 10 amps. It’s burned out before. I plugged in a 15A fuse. Checked it and got power. Plugged in another fuse, which is still in place. Drove to work. second speed doesn’t turn on Got the fuse. well, it’s not a bastard, it’s burnt out!
Considering it’s burned out before and with a different control unit, there’s a good chance it’s not the control unit. Most likely a short somewhere, and most likely in the rocker, t.к. It didn’t blow right away. That is, something moves, probably short-circuits and bang! Now I’ll have to look for that damn short circuit. One of the most frustrating stories is when it “floats”.
Radiator Cooling Fan Control Module Relay for Ford
There’s another problem. At heating up of coolant 90 starts rattling of contacts of switch on of the converter clutch (of course, when the converter is on). The clutch is “ticking”. turns on and off with frequency of about 2 Hz. Extremely unpleasant effect. The only reason I can think of is the thermocouple in the F165 sensor is screwed. It’s good if it’s in there. Because the second possible reason is that the contacts in the pressure sensor are screwed. And its replacement is already refilling of the system. But let’s hope for the best. And prepare for the worst.
I don’t want to jinx it but it seems that the short circuit was found rather easily. a light bulb of the rocker panel illumination, dammit. The last time I was in Pushkino, I took one as a spare, but I had no time to put it in. Now we have to.
I drew more or less BUV completely, with passivation values, but types of all diodes are not clear, but something similar to KD521, and one more powerful diode, I can not read, on the back side of the board stands uncomfortably. But it does not matter. One diode is not clear at all. Looks like a regulator, but stands exactly like a diode. In the picture is circled in red. I also could not find the color marking to identify it. White and green stripes. The case is glass. It is said that most likely it is a smd diode. Housing and type MELF DO213AB
How to choose a new sensor
In order to find the right sensor, you need to know the optimum coolant temperature at which it should turn on and off. For VAZ 2110 it is 92 and 87 degrees. Optimal sensor actuation temperature for another car listed in the instructions for repair and operation of the car. Buy the sensor only from major stores and be sure to take the receipt. Before installing the sensor in the vehicle, check it as explained above. If the difference between the temperature indicated on the sensor and the temperature at which it actually operates, more than 5%, replace it. Operating the motor at a temperature that differs from the optimum, greatly reduces its life.
Cooling system diagram There are many components in the cooling system. Among those of interest today, which can cause malfunction of the radiator fan, we note:
- An electric fan. This unit turns on when the coolant temperature reaches the 100-105 degree Celsius mark;
- Fan activation sensor. It is set to actuate precisely in the range of the specified temperatures. The sensor is located on the cylinder block inlet (marked LS0112 from the factory);
- Fuse marked F7. It is located in the mounting block;
- Relay fan. You will find this unit already in the cabin, under the right panel of the front console.
If your VAZ 2110 does not work the radiator fan, the cause of malfunction should be sought precisely in the above elements of the system. Although there may be one situation in which the electrical circuitry has nothing to do with the malfunction.
4-WIRE CONNECTOR (NORMAL FOR LIGHT, SIGNAL).) PAD WITH WIRES, BUTTON.
If the fan itself is the cause of all the problems, there is no need to replace it because in some cases it can be completely repaired. Breakdowns are often related to the bearing or brushes.
If the cause of the failure is a motor failure due to broken wiring or a short circuit, you should not risk repairing it. It is easier and better to replace the whole disc.
If you drive a car that does not have a cooling propeller, it will lead to overheating of the refrigerant and the destruction of nozzles, rubber elements, the main cylinder block gasket and valve cover. Nearby and before the destruction of the components of the piston group.
It is strictly forbidden to operate the vehicle with a broken fan.
Soft-Start Relay for Vehicle Cooling Fan
High load on the onboard network (alternator, battery, wiring). 2. High mechanical stress on the bearing and on the electric fan mountings. 3. Use of unreasonably large fuse. Starting motor current 20. 30A depending on model, and rarely exceeds 4. 8A on the run.
That is why it was decided to build a kind of “soft-start”.
The task I set myself was as follows: 1. Use of factory wiring 2. Do not put on additional buttons. 3. Originally, this model of car did not have a relay to turn on the fan, so there is an opportunity to fix it.
The device is a PWM pulse generator. The PWM starts and begins to generate a pulse at output 3 with a constant frequency and a time-varying pulse repetition rate. The time is set by the capacitance of the capacitor C3. Then, these pulses are fed to a high-powered field effect transistor driver, which drives the load at the device output. Driver for IRF4905 is made with domestic KT315 transistor. The time of full gate opening of the IRF4905 depends directly on the capacitor capacity and the speed of its charging. The diode at the output is used to smooth out the back pulses of the motor. I used a Schottky diode assembly with a common cathode as a diode. The poleswitch is P-channel, because it has to regulate a positive voltage. I could use a N-channel as well, but then I would have to redo all the wiring for the cooling electronics. All outputs on the schematic are given with consideration of the relay contacts outputs. The circuit is simple and made as SMD so it is possible to put it on a board the size of a car relay. Some of the circuit is tightly wired into place, while the other is built on a small circuit board.
The board I drew LUT, all known, then etched with ferrous chloride. On this site I have met many people who have etching process takes more than 2 hours, but for me personally it takes 5-7 minutes. The thing is that to etch the board (no matter what size) you need to heat the solution to a temperature of 60-70 degrees, while you need as often as possible chatty textolite in the solution, and periodically look at him.
The first thing to do is to take out the relay. It may or may not work, but we are not interested in it. The main thing is the size! Now we need to disassemble it and carefully remove the inside, leaving the output terminals.
After we cut off all the unnecessary things, let us do the mounting. The hinged part, will be the whole right side of the circuit, everything that comes off the 3 pins of the NE555. “Why you can’t solder everything on the board?”Because it’s not going to fit in either length or width. This applies only to a standard (sized) relay.
The mounting part is almost done. Now let’s get to the board itself. In my case I had to cut the ready made board to size because the transistor and diodes were put out of the board. The board itself, which is displayed at the end of the article, is full size so that it could be adjusted to the dimensions.
Now we solder the cutted board into the relay.
It remains to solder the jumpers and we can move on to fixing the radiator (through the insulating gasket) and cutting the relay cover.
Actually the device is ready. It remains to varnish it or fill it with rosin. Although, if the relay will be placed under the dashboard, then the varnishing can be excluded. After the final assembly the device doesn’t need adjustments and fits to any (in terms of power) electric motors, because it has a maximum current of 74A! This is still a car, there should be 200% power reserve. So that nothing works at its peak performance. IRF4905 is pretty cheap and widespread, there should be no problems with its acquisition.
Check unit installation and adjustment
Before starting the vehicle’s engine, make sure the unit is properly connected to the vehicle’s system according to the above points. The unit has a function to check the correct connection and operation of the unit itself.
Without starting the engine (ignition key in position 0), turn on the parking lights. At this moment the fan should turn on medium speed. If the fan does not turn on, the system is not installed correctly or there is no contact in the wires.
Second part of the test
Leave parking lights on and turn on the ignition (ignition key position is on) without starting the engine. The fan should stop. This indicates that a good contact to the sensor is made. If the fan does not stop. it means that there is no contact to the temperature sensor. Verify that the black wire is securely connected to the temperature sensor wire via the contactor.
After checking the installation of the unit, check the correct direction of the fan according to the arrow on the impeller of the fan.
Final check and adjustment of the control unit
Then do one last check and adjust the unit to your chosen temperature (the button and indicators are shown in the figure below):
After the above steps to install and check the unit with the engine running and the unit (parking lights) on, press the programming button once (press with a blunt object with a diameter of 3 mm). After pushing, the fan should turn on at maximum speed.
Then press the programming button a second time. The fan should turn off and the two indicators should light up. The unit is ready for programming.
Wait for motor temperature to reach bottom line (85 degrees recommended). When this temperature is reached, press the button a third time. Then one of the two LEDs goes out. This shows you that the lower temperature limit is selected.
Wait until the engine temperature rises to the maximum expected level (95 degrees is recommended). When this temperature is reached, press the button a fourth time. The last LED goes out, the fan reaches maximum speed and starts to cool the engine. During cooling, the fan speed drops to the lower limit temperature.
The unit has been programmed and will continue to operate at these settings within the temperature limits you have selected. You can reprogram the unit for other temperatures if needed, then you have to start with the first item.
Activation of the fan control unit:
Switch off the fan control unit:
If the fan does not work when the parking lights are on and the ignition is off. The control unit is defective.
If the fan runs with the parking lights on and the engine cold when the ignition is turned on, then the contact between the temperature sensor and the control unit is broken. If the contact is good, then the control unit is defective.