Fan does not speed up when AC is on, is this could be the source of overheating problem?
Hi, i have ford explorer 2006 4L XLT car and recently i noticed overheating
problem mainly on freeway with AC on. My mechanic changed the thermostat
and coolant but still i get the problem. I noticed the cooling fan turns on on
cold start and does not speed up when i turn the AC on, is this normal or how
does exactly this mechanism work?
Usually when a vehicle overheats at expressway speeds it's a coolant circulation problem, a collapsing lower radiator hose, or there's air trapped in the system. I'd suggest you flush out the cooling system with a chemical cleaner to get any rust and junk out of the cooling system. BUT be prepared for something to spring a leak. If you a weak spot in the radiator, water pump, heater core, etc. It may start leaking. HTH. -Jim
Thanks. However, the mechanic searched for a leak using pressure test and there were no leaks. I am concerned about the fan because I can not spin it freely when the engine shuts off. Also, the fan does not speed up when AC on max.
In a cooling system that's restricted by rust and junk you may not have a leak. But you will have poor heat exchange. The air-conditioning puts an added load on the cooling system which will exasperate the problem. When traveling at expressway speeds the fan(s) aren't even an issue. They're there for low speed and idling situations. If they're electric cooling fans you should be able to spin them by hand (with the engine off and COLD). If it's a clutch fan you may not be able to spin it by hand. HTH. -Jim
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