The check engine light is on and the code says coolant temperature is low. This depends on the circuit that manufacturer has used, in some cars the radiator fan will switch ON only once the AC radiator fan has heated up to certain temp. The second time the fan comes on is with your AC. But the engine fan will come on only when the computer tells it to. The fan should turn off after the engine is shut off. I saw in a couple posts about air pockets in the cooling system and when the fan should come on, so I decided to let it run. Fan does not turn on at any other time that I know of, or that I can hear while driving. Why Won't a Radiator Fan Turn On? Turning AC off doesnt stop fans Only turning off the truck stops them. Fans only kick on when AC is ON. For the radiator fan, there is a relay and a fuse. You can visually check the fuse. Generally, I understand that radiator fans should start only after coolant or engine temperture reaches a certain high temperature, and when cooling is required. As for the relay, I would swap the radiator relay with the A/C relay (they are the same on 2007 Accord). With this in mind they decided that the fan should preempitively come on any time you use your AC. 1) Its ok, but neednt cut in immediate also. You may want to check those. (2004 Honda Civic) I'm having issues, and am at a deadlock. This small structure can wear out after prolonged use. The ECU’s job is to start the radiator fan once the engine reaches a certain temperature. Set your air conditioning to the MAX setting and turn it on. The radiator fan should come on. You may want to check those. On many Hondas, both fans turn on when the AC is first turned on and the compressor is running and temp set to low and heater/AC fan turned on. Shouldn't radiator cooling fan be … read more should the radiator cooling fan always run when the a/c is on? The AC fan should start when you turn on the AC. @johnblack I checked it while it is on cold state, but then when turn the AC ON the Radiator Fan turn on, so I let the AC ON while i drive my car, after 30mins driving if i turn the AC OFF, the RADIATOR FAN still dont work, even the Radiator Temp was hot. One note on the fans. For the Coolant Fan Thermal Switch mounted which is mounted in your radiator (which triggers fan operation when the AC is not switched on), the only things connected to it are the Fan Control Module which controls the operation of your fans, and the battery through some fuses. (Not Recommended) Setting the FAN to “ON” is not needed to run the AC or HEAT. At least until around 2009, as was noted earlier, if the engine is overheating, then the radiator fans should run regardless of whether or not the AC compressor is connected, or is turned on. My car started overheating on about ten hours into a fifteen hour trip. The condenser fan is the smaller of the two. The engine fan shouldn't come on right away because the goal is … It seems like I could always hear it running when I pulled into the garage when the AC was on. - 2005 Chrysler PT Cruiser When the thermostat is set to “ON”, the FAN will run at all times. 2012 eco. I think it has a radiator cooling fan issue. When I get on the highway then the AC works. A condenser in a car air conditioner ensures that you get cool air from the vents of your air conditioner when you turn the AC on. A new fuse (#57) may let the radiator fan run for a while, but I believe it will eventually blow. Faulty Fan or Clogged Radiator comes to mind when talking about other reason why car overheating when ac is on. On your yr crv I believe it is on the passenger side. My car has been over heating when my AC is off.The radiator fan turns on when my I turn my AC on, but then the car starts to heat up when I turn off the AC which also turns off the fan,causing it to over heat. 2 Answers. If you have two fans. When exactly this happens is different for different cars. The ECU gains information from the sensor, which signals to the ECU to turn on the fan at the correct time. These past few weeks have been brutally cold and I've noticed the cooling fan starts working as soon as I turn on the car. Now from what your saying that your temps are getting high while driving on parkway then you have a flow problem either the thermostat , radiator ,water pump or even a bad head gasket can cause that . Anyway when I turn on the AC, only the one on the passenger side starts. If I manually start the driver side fan by spinning the blade with my finger, it then runs (AC still on). When AC is on, Radiator fan does not come on. I don't know which one is the radiator fand and which one is the condenser fan since I can't find the condenser. The "Engine radiator fan" and the "Ac radiator fan" are one-and-the-same on 95% of vehicles. If the A/C fan … A car's electric cooling fans are responsible for ensuring air flow over the radiator at low speed, and failure will almost always cause overheating while in traffic. On older vehicle models, just wait about 15 to 20 minutes for the engine to reach operating temperature. 2013 F150 AC & Cooling fan issues - 2013 F150 5.0 XLT 153,000 miles This past summer the AC was blowing warm. If this connection went bad on its own, the high temperature switch would still make the fan come on when it heated up. I bought a preowned s320 recently, and notice that the radiator fans started to turn about 5 seconds after ignition switch is on, and even before starting the car. no, when the AC is on they both seem to work , even when the temp goes up, or if you turn off the AC , then the fan stops turning. I found underneath the Thermostat housing a single wire going into the engine block, is this the sensor switch. WIth a meter it looks like most everything checks out. to nonvtec: One fan is for A/C, and the other for radiator. Seeing the fan won't turn on in city driving the ac doesn't work well at all. The condenser fan usually has smaller blades and more of them. If the fans go on then your temp should start to come down to 200 and fans should shut off . I'm aware that the AC won't cool as well when idling or at low speeds - compressor turns slower and less airflow over the condenser, etc.. This is during 60 degrees outside temp. With engine at idle/operating temp and parked, AC and defrost not turned on: Fan does not turn on at all. My cooling fan is not acting as it should. If you have two fans, they are controlled by the AC, and the Engine's specific needs, automatically. For the radiator fan, there is a relay and a fuse. Fortunately, these systems are fairly easy to diagnose in the event of failure. Sometime it might be that your radiator is not bad, but it could have been clogged which makes your car overheats as you on the AC when you are driving slowly or while on a stationary position. If it does the relay is working. No overheating problem at all. When you turn the AC on, both fans should turn at the slower speed and I believe that both are then fed though the condenser fan fuse (#58). When I run the AC is really lugs the motor, but that might be normal or a separate issue. When driving, temps stay between 199-209. Yes, it's the condenser fan in the front of the radiator/condenser. The cooling fan should come on immediately or within the next couple of minutes. It's toyota camry 2004 XLE 4 cylinder. (Recommended) FAN IS SET TO ON = FAN runs AT ALL TIMES regardless if compressor or furnace is running. I stopped, changed the thermostat (because the heat was blowing cold, thought it was stuck shut.) Toyota Camry 2004 radiator cooling fan only runs a few seconds while AC is on. Cooling Fan Not Working with AC On Thanks for the diagram! Turn the AC on and the electric fan on the radiator should run. If the A/C fan still comes on, then it is not the relay. Let the car cool down, and finished the trip with no problems. You can visually check the fuse. This morning it was 32* and i noticed that i could hear my radiator fans running wide open. The main problem is that, when I turn on the AC the Radiator Fan turn on as it should, but then after a while it turns off and the car overheats. I have no picture to tell if I'm on the right trail. Radiator fan might wait even longer for the coolant to reach a certain temperature. Once you replace the relay, the radiator fan should start working again. It takes a long time for the engine to heat up. Temperature Sensor . My car has a manual transmission. Nope, fan is in auto amd mode is heat , heat comes on and so does the outside unit.not a heat pump , also i am getting 22 v at C and Y …at C and W i am getting 24.7v … it should be a bad tstat..but when i jump off at board with tstat in off mode.Y to C , heat also comes on with out side unit. Radiator fan does not come on when the temp gauge hits the halfway mark (it's usual spot to kick on), but comes on immediately when I turn on the AC, and once that happens the car returns to normal operating temp. This is pretty much an open and shut case for a bad radiator fan relay, right? by Richard Rowe . I have a 1998 Ford Mustang Cobra 4.6 with a DOHC. It only comes on when temperature rises to operating range. AC and defrost is off. Your air conditioning creates extra work, and heat, for yur engine. 2006 PT CRUISER - NON-TURBO. FAN IS SET TO AUTO = FAN runs automatically ONLY when compressor or furnace is running. to nonvtec: One fan is for A/C, and the other for radiator. Then, the fan should come on. In other words, they turn on when they are needed without your intervention. THe fan actually came on at 214 F. So I … @ Tallra1 I already checked the wirings, and its all in good shape, but i havent check yet the main thermo-switch. I have to turn the A/C on medium fan setting in order for the engine fan to cool the temps back down to 200-210. My car has 180502 miles. Image by Flickr.com, courtesy of Peter Morgan. Radiator fan only comes on when Ac is on. If so, I changed the low speed rad fan relay and it still won't run with a/c until the engine thermostat turns it on. While sitting in backed up traffic, temps based on the digital dash go up to 226. 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