before any of you blame the fan module or the ecu/ecm, go under the car, take off the plastic cover thats directly underneath the radiator where fan/rad/condenser is, and check the connector plug/wires leading to the fan, and also the temp sensor for the condenser. spray bit of wd40 inside the plugs and behind where wires lead into, push/pull out both plug connectors multiple times, TRY THIS FIRST!! mine was a bad condenser temp sensor connection
Djordje Ivanovic Thank you. On what model? I have a W204 2009 C180 Blueefficiency (1.6 petrol) amd fan runs on high. Trying to find the cause myself and read could be the AC pressure switch. I will try your suggestions first. What model do you have?
W203 2006 C220 CDI, also try while the car is on and fan is on high, try grabbing the wires right behind connector for the fan/also moving the connector and find which wire is bad, try both fan plug and plug for temp sensor AC condenser
Djordje Ivanovic Mine starts on high few seconds after turning the engine on and stops soon as I turn off the engine. Thank you. I shall try :D Have a nice weekend.
Djordje Ivanovic Took it to a good garage. Came back with few faults not related to the A/C and one related to it and it seems to be what I was guessing:the A/C pressure sensor(switch). Car is booked for Wednesday now when the guy whos qualified to operate to operate the A/C machine on their site is coming back from holiday. Send a text here around Fri so I remember to keep you updated and hopefully jumping around that I solved it :P
I had this problem in my 2004 e500 4matic after my battery died, I jumped it and the problems appeared , the battery may have died of a parasitic battery drain ( to be analyzed in the future but its not there anymore ie the drain ) but this is how I had it finally fixed the high speed fan problem, it wasnt the ECU, not mass airflow , not radiator fan control unit, not the coolant temp sensor , the 3 simultaneous fixes involved unhooking the negative cable of the battery , a/c freon systems recharge if low causes fan to go high speed and replace the air pressure sensor , the combination of the 3 fixes the high speed fan permanently ,- there is too much automatic assumption its always the ECU and the others I mentioned that does not fix it IMHO now my fan turns on when it should and goes faster if I turn on the air higher and when its super hot outside as it should not when you do a cold start and within seconds it starts to go booming speed like its about to turn rubber and burn the fan out if used a few more time and you feel youre about to smell burning fan rubber - save alot of money on the recommended by many poster fixes on ECU ,Fan controller and mass airflow and other fixes that most likely arent the fixes, the a/c freon recharge if low may be the first one to try if unhooking the neg battery cable to reset system doesnt work then the air pressure sensor , if you do all 3 likely success is high IMHO
finally fixed the high speed fan problem, not ECU, not mass airflow , not radiator fan control unit, not not the coolant temp sensor , the 3 simultaneous fixes involved unlooking the negative cable of the battery , a/c systems recharge if low causes fan to go high speed and replace the air pressure sensor , the combination of the 3 fixes the high speed fan permanently ,- there is too much automatic assumption its always the ECU and the others I mentioned that does not fix it IMHO
I've had the c230k for almost 6 years, a c240 (sold) for maybe 4 or so, I've always had the fan on high due to bad ecu. I bought the car (c230) for only $1000 (almost 6 years ago), the ecu fix is not worth it (to me). it keeps the engine cold, the less heat it encounters the longer it will last in Florida, due to less strain on parts from heat. I don't mind the sound. older people probably do though. my solution would be to just put a switch on it. you can run up to 90 Celsius without issues. and unless I'm stopped for more than 7-10 minutes at a light/traffic highest I'll get is 87 degrees Celsius in the summer, in Florida.... with the fan always on it was rare to see the engine go past 68 Celsius. my model has an m111 engine with is 2.3 L which is considered to be the robust version where others have 1.8 L(m271). difference is from forums etc I understand mine to be less likely to break under same circumstances of the other. there's enough space if you remove the fan to just run another fan that has variable speeds via switch or your own coolant sensor. I may do that. just so when I want to chill in the car and listen to music I can without the fan draining the battery. sometimes in colder months I just remove the fuse to see what the car sounds like. it is a 15 amp fuse in front fuse box (under hood, driver side). once removed fan won't cut on. I have a muffler delete. but I just like the s/c whine. I don't believe you can have these cars and not run into a few problems. but over 6 years at buying the car for only $1000 I'm not complaining. I just turned 21. worst pain I felt was when the key broke. that ran me $550 because I had to tow it to dealership in order for them to see its my car along with run the ecu to program the key correctly with mileage etc, along with title to order a new key. also if you have one (w203/cl203)in working condition, DO NOT let it sit. drive it around once a week even for just 20 minutes. make sure ants aren't in any part of car! they can do damage. these cars can last a while. only time I see one gone its because of a crash. I've never seen a part out because of an unfixable problem.
These fans have 4 wires running to their fan controller usually on the fan itself. This fan controller is computerized itself. Two wires are fat and are the main power wires. The other two are the control wires. -One is a 12v that either has 12v on or off to switch the module on or off. -The other wire is the speed signal wire(usually called M47 wire) that carries a special PWM signal around 5v but it varies in voltage. The PWM signal also varies in duty cycle between 10% and 90% which tells the fan to vary speed between 10% and 90%. Some multi-meters have a setting that allow u to measure the duty cycle. HOWEVER: The controller is smart, if it receives the power on signal but no PWM signal it will default after around 3-5 seconds to 50% speed. So if you want to wire it up to a switch, disconnecting the 12 on wire will give you off, connecting the just the 12 on wire will give you 50% speed, while hooking up the speed signal wire will give you 90%. If you are trying to use the fan on another vehicle or want more control there are expensive fan controllers made especially for these fans, you can also use an Arduino to generate the PWM signal, and use a temp sensor to vary speed.
Hi Spenser Roger, I'm having an issue with one of these - does not turn on at all. I have tried unplugging the temp sensor (which should cause the fan to turn on to 100%, since engine management doesn't know the temp), and nothing. I'm getting power and ground (2 fat wires) I'm also getting ignition (1 skinny wire) and I think I'm getting PWM signal (1 skinny wire) - but I'm measuring with just a basic multimeter, so don't know what the pwm signal is sending. I do know that the signal is different if the coolant temp switch is plugged in or not. So is it time to buy a new fan at this point?
@@kirillbrodski I'm having the same problem as your having but I have to add that my air condition also stopped working at the same time as my radiator fan. This all happened when I went through a large puddle about 10 to 12 inches deep. Another thing that's happening is even if I have my car in a cool garage, as soon as I start the car and touch the a/c condenser it is super hot within 1 minute. I also tried disconnecting some of the antifreeze sensors and it did not make my fan turn on like it did a long time ago when I disconnected them. All fuses and relays are good. I also checked the fuse that I think is 125 amps and located in a black box near the battery and that was also good. Some people show a loose solder in the middle of the fan on the electronic circuit board. I put five volts to the pwm wire which I believe is blue/green that is going to the fan but the fan still did not turn on. I am getting power through the thick red wire and ground to the thick brown wire and also 12 volts from the black/red wire which are all going to the fan. Next thing I'm going to do is remove the fan and see if I can get at the circuit board.
@@georgelast9991 I've since sold the car, but for me, one of the "pre-fuses" (black box near battery) was broken. I was able to check the signal with multimeter that can read the PWM. So in the end, the fan itself was fine. Though for me, AC was always working fine.
Hi Jeff, working on a 04 s500, just replaced the fan, comes on when engines at temp but ac not getting power, wire says ground, clutch clicks when i put 12v to it but no circulation. And fan goes on high when i unplug the ac bottle temp sensor. Do you know which fuse/relay i should be looking at? Cant find a real diagram anywhere
There is a range of Vin numbers that can potentially have a faulty ECM. I would check that first. This happened on my C300 after water intrusion damage. Still diagnosing it but it seems to be a bad front SAM/CGM.
@@JD-ed6ce make sure the cover for your front sam (driver side fuse box)is on correctly. If water enters the front sam the car starts acting up electrically until it dries up. If that doesn’t work it can be a faulty sensor tricking the ecm to demand 100 percent cooling fan.
My 2017 g wagon keeps doing it randomly. Sat in the car on the phone if I turn the key or open the door it shuts off. I got out waited a few min it came back on..popped the hood engine cool, closed the hood it stopped. I don’t know how long it stays on or if it’s still doing it. I was told I need a new battery soon recently changed the aux battery could that be the issue?
Mine stays on even with the key taken out .... I have to pull the battery terminal. It just happened last night after I went thru a car wash - - maybe water caused it. Any ideas ?
@@hiredxgunn Yep ..... I thought I answered someone way back ... but it went something like this. I had been inspecting the fuses for a problem and had left the cover off so that I could continue the next day in daylight. However, I had forgotten about the cover and went into a car wash and it seems the water poured right then thru the hood vents right into the fuses. The result was my radiator fan was blowing all by itself and so hard I thought it would blow up. My common sense low-tech cure was the next day when I saw I still had the problem I simply sprayed all the fuses with WD-40 and then drove the car with the warm engine air blowing all inside as it does. It died out the fuses and it has been fine since.
Hey Jeff, my 1998 W210 E350 fan comes on as soon as I start driving. Even the simple act of jerking the rear axle and spinning one wheel seems to turn it on. I've also noticed that it runs fine if I remove the ESP control module but the car won't change gear. It'll be in limp home mode all through. What could be the problem? Thanks.
My fan turns on only after hitting 100*C,thats a new thing,usualy it kept 80*C,but now goes to 100*C-fan turns on and keeps the car at 90(ish)*C. Is it a Thermostat problem ? Mercedes w203 C200 Kompressor
Foreign Enterprises idk exactly what it is but the fuse is in the front of the car where u open the driver door. look it up on your list of fuse options
@@bradleyn3577 I had the same issue, I switched out the 15amp fuse, put in another and it blew up right away I tried this 2 other times and same thing? I recently changed my battery could this be the issue or is it a short circuit in the AC module which will need replacement if that’s the case :( so confusing
Hi jeff i'm having a BMW E90 330i 2005 car. also i'm facing to exactly the same problem as you. i check my car many times it went trough pressure test, bleed the system and had to replaced water tank, temperature sensors but still car having the same problem. i don't no what to do.. please help
I have 2004 Mercedes Benz clk 500 , does the same high idle with the fan every time I turn it on , also I changed spark plugs and sparkly the maf sensor and still high idle on fan and I don’t have a maf senor or engine light on my car , only light 💡 I get on my car is check engine coolant light and esp
Mine fan runs at a low speed only and only when the AC is on. It doesn't turn on and it happened right after I changed the serpentine belt myself. Can anyone explain why this may have happened?
Jeff, my 02 c240 turns over but no spark and also the fan turn on on high also intermittently it will not even crank and the obdII is not Communicating ...
Hello from Canada. Though not that exclusive in terms of construction I have a 2010 C250 model exclusive to Canada. And this problem has presented itself, ten plus years after first being observed. Buyer beware, these cars are no longer of good quality anymore but of status symbols. Take it from first hand advice,do not own one that is not under warranty!
ECM - Engine Control Module(ME) 1 problems exist 1.P203E-004 No CAN Message From Instrument Cluster Or Message Faulty. Communication Fault / See Also CAN Status In Freeze Frame data(P0600) this if the problem using my TopDon scanner - not sure if I burned the ECM when I jump started my battery and car ??? causing the radiator fan to go warp speed
This is a very common problem with the C240 and C320. The fan runs on high and the dash light says visit coolant workshop. This is definately a bad ecu or ecm . The only way to fix it is to replace it with a new control unit part number A1121532679 or A1121530879 If you are not sure we can test the ecu for a small fee.
jeff m Hello my car fan works low speed in high engine temperature. I change fan to another new but after week this new one worked like that and in dashboard show my antifreeze in low position what does it mean ?
Hi, great video but what happend to me today? car running fine, checked the fault codes on my engine, Mass airflow sensor (hot film) and EGR fault... took sensor away and tried to spray it with brake cleaner to clean it.. but nada still the same problem and faults cant get away.. had 12v supply and 5V supply.. and somewhere here something happend... fans run on maximum speed both when engine is running and just with only ignition on.. FAN ENGINE fault on instruments cluster pops up direct, the ECM livedata say Cooling fan (actual) value 90%... now the 12v supply to pin2 is gone, 5V is there.. Checked all cables from sensor to ECM but they are fine.. seems like the sensors broke down completly now or something... never had a engine fault in display before but I always felt that he was more thirsty on fuel when comparing to other friends.. do you think my sensor was bad but now broke down completly ? its a 2001 270cdi w210... so its hard to notice the difference with engine when its a diesel..
mine happened after jumping my dead mercedes car battery ie could that have fried the ECM everything else works perfectly except for the radiator fan unless it was a coincidence only , the check engin light also went on for the very first time since I had the E500
Hi Jeff. I have a similar problem with a Mercedes c240 98 model. the fan runs at high speed after a few minutes after starting, then turns off while engine running, then the check coolant light comes up though there is enough Coolant. sometimes the fan runs for a few seconds, sometimes runs longer
Hi Jeff, great video, this may help solve my fault? I have a Skoda Octavia, Diesel, PD, 2005, recently the A/C fan cycles to very high and then slow, then high etc. Checked both coolant temp senders and the A/C Sender. Checked all plugs, and earths, cleaning and refixing. Also, cannot get any heat into the car, only very cold air? The Coolant and A/C fans, A/c Condensor and gas are relatively new. This is very interesting Jeff!
if everything else works fine , after jumping or charging your dead battery and the high speed fan problem comes up , once the battery is fully charged and the system cycles thru , the problem may go away by itself if nothing else is wrong , test the fan relay or fuse to the ECU first dont waste money replacing the ECM without trying these 3 first IMHO
I have a CLK350 convertible which I bought used. I have taken it to Mercedes twice, and have been told there is nothing wrong, and that the fan runs full speed by design in this model.. Are they BS'ing me or is that true?
Luis Urbina , mine does tge same thing after it warms up. I was trying to see if there's a problem, because it's loud... but stops after I turn the car off.
I have a 2005 E320. When I turn the air conditioner on the fan runs at high speed and makes a funny sound. And when I turn it off its slow down. and the noise subsides. What could be causing this problem.
That's the way it supposed to work. Since the AC puts more strain on the engine, the engine heats up, so the computer turns on the fan on high to help keep the engine at it's correct operating temperature.
Mercedes C240 cooling fan runs constantly on high speed due to a bad ecm. There is a common problem with the fan for 2001 and 2002 Mercedes Benz 6 cylinder engines.
I have w202 c200 2000 years when engine heated fan working in low speed .When i am in traffic my car began heating and fan not change speed in high level .What to do ?
I have same problem, have you found the solution? I have replaced fan&fcm, coolent temp sensor and thermostat and water pump, I will be replacing ECU soon
More than likely the ecu , engine computer is the reason why the fan runs on high. Does the fan run when the key is in the on position or only when the car is started. What type of Mercedes do you have. Year and Model?
Hello jeff thanks for the informative videos i just got a problem with my Mercedes cl 203 sport coupe 2002 today,i took all the relays out put them in all again ,unfortunately i forgot one relay and start the car, suddenly the fan start to run in hight speed and the engine doesn't take electricity to start. now when i switch the car fun runs in very high speed and engine doesn't,start it would be your kindness to help to solve this problem. Regards
Quick question. My 1998 C180 sedan has a thermo fan which starts running 30 seconds after the motor is turned off and won't turn off. I have to disconnect the battery. Any suggestions to help out in my hour of need? It's Friday and the garages are closed till Monday
My W168 does that but it only does that after start up every time for a short while then it is fine (fan slows down to normal / off ) O.o. Please help ^^
I got a 2005 c240 & I tried to start it earlier but it didn't do anything ? then the fan came on but still doesn't start? did this problem not long ago but it had water where the battery goes & I drained it & it started right away ? but this time it didn't now the fan comes on ?
You were right on the money, after ac was charged my fan was on the full blast all the time I let some Freon out and car runs perfect. Thank you so much
I'm having a huge issue with my C280 Luxury 2006. Here is a 2min video of the issue www.youtube.com/watch?v=rrgfY... It won't crank or start at all. As soon as I put the key into the 3rd ignition position. The car wont crank BUT the COOLER FAN is sounding LOUD like a Jet Turbine. I did the following changes: 1. Checked and Boosted the Battery 2. Fully charged the battery for 45mins at advanced auto parts 3. Checked all fuses and replaced any that had issues 4. Replaced Fuse 52 for a new 20amp one 5. Checked ignition relays and put new Siemens relays. 6. I don't know what else to do I took it to the Dealership for a mercedes recall on the sunroof that was detaching and not working. They took 4 hours to work on my car. They said they needed some glue. I took it back from the dealership for the 14 mile drive. Since then the car won't turn on at all. Please all your help is appreciated.
My E320 cdi runs fine but occasionally when the car is locked and I walk away the fans kick on on full power. If I catch it I can start the car and it stops. Yesterday I didn't catch it and when I got back to the car the battery was dead and fans still turning slowly.
The only way to fix the problem is to repair the ecu or replace the ecu with part number A1121539279. This is up to you. The ecu protects the engine from over heating and so the fan runs at full speed. Your ecu is no longer controlling the fan. If you don't fix the problem then the fan will quit working also.
IMHO if the ECU doesnt send a signal to the Fan to run it fast , its not the ECU, its the Fan control module/motor thats faulty , only if the ECU is erroneously requesting the Fan to turn on even when the air is not on and its not hot because you just started the car , then it cant be the ECU it has to get erroneous request fromt the ECU for it to be the ECU problem , other wise your throwing your money away on a new ECU when its the Fan control module ie motor on the Fan , is my laymans answer based on watching a bunch of too fast fan videos
