with air conditioner turned off , when the radiator fan turns on... should both fans on rad turn on? or just the rad one while the air one stays off? reasoning is... when the rad fan or fans turn on when im parked or idling... they give a loud "clunk" feeling... i can literally feel the car vibrate and headlights dim for split second. I know this happens too when im driving at night as headlights will dim every minuite or two for a split second..., allthough i dont "feel" the fans come on when driving. So the other nite when i parked in garage and was just about to turn car off... i "felt" the rad fan turn on and seen the lights dim on wall in front of me... so i opened up hood and while car was running.. i waited till it happened again. about a minuite later both fans turned on... stayed on for about 10 seconds... then both shut off. they do this even with the air condtioning shut off and dash blower turned off too. Is this normal? Ive been informed by a wannabe tech at work that only the rad fan should turn on, not both. Ive called the dealer and they didnt know, only to bring it in on its next service sheduled call and they will then check it out. Anyone know if its just me concerned about this, or is it normal????? thanks.

 

Depending on how the car is designed I believe the engine temp decides if one or both turn on. But the radiator fans have a high current pull so when both come on your lights will dim.
Your cars fans most likely wont kick on as much while your driving, you have to keep in mind that those pans exist to help cool down your radiator by pulling heat off of it and cooling the water/coolant running through there. When in part there is a good chance of feeling them kick on because there are no other vibrations dampening it.

I would try to find out how much current each fan pulls, ant if its around the 10 to 15 amp range then yeah, the lights dimming when those kick on is definetly normal.

 

Also, the AC condenser will kick on and off a lot too when..well using the A/C. That's probably what you're noticing the most when your headlights dim and your car idles fairly low.

 

It's normal, don't fret.

 

ok. what about when its just the defrost on? Went to car today.. turned on... opened hood... then turned just the defrost on while car was still cold and both fans came on. Normal??????????

 

Your Air Conditioning automatically comes on (hence the condenser fan running) when you select defrost. Again, Normal.

 

thanks for the reply. you said "hense the condenser fan running"........ which one is the condenser fan? Left or right? As my previous question had mentioned... should BOTH fans come on when car is started and turned to defrost??????? (last question...... haha)

 

when defrost is turned on a/c turns on automatically. cause there is nothing better for getting condensation out of the air then running over a nipply cold evaporator. what are car is doing is completely normal. i do like that your monitoring how your car behaves so diligently though. thats the way to notice when things are going wrong before they break. now you are always going to feel the fans coming on. but your looking for some answers, and this is a good place to get them. if you feel a little shake when the fans first come on that is ok, but if the shake continues for the entire cycle, well then a motor mount may be going out, but if its a 2005 then this shouldnt be. also, as the fan motors get older, they start to draw more current, because an old electric motor just isnt as efficient as a new but, its a 2005 so......probably not. which now leads me to what i think could help out.......your battery, those fans run off the battery not the alternator..a nice well maintained battery should easily be able to handle those fans turning on. but one that is about to go out probably wouldnt. and IF YOU HAVENT BEEN FILLING UP THE WATER ON YOUR BATTERY....then this might be the problem. and they dont fill it up at the dealership because they want your battery to go out just at the warranty expires.