zapc

been reading old threads, no definite answer. Is my main fan supposed to come on when AC is turned on? mine does not. fan works as supposed to
but at idle when AC is on it gets to 225 very quickly, as soon as fan kicks on temps drop immediately. my aux fan comes on at 235 but by then AC gets warm because of lack of air across condenser was thinking of changing sending unit for aux fan but ive read all the threads about that, on how it may stop main fan from coming on. dont really drive in traffic that much with AC on so i may just wire Aux fan to a switch just for the traffic with AC on situation.. yes this has been beaten to death .
sorry

GREGGPENN

The main fan is programmed to come on at 225...even with the A/C on. That means your main fan is functioning correctly. When both the main and aux fans are on, I doubt that you aren't getting enough air across your condenser.

If you haven't already, look into removing/cleaning your radiator/condenser air pathway. Also, make sure you are fully charged with freon.

Also, there's a LOT of heat in the dash of a HOT car...that's sat in the sun. Also, a lot of heat in the interior. A/C is supposed to blow something like 50-55 deg air out the vents. When it's HOT outside, that air can warm up by the time it hits your face. So, consider measuring vent temp as well.

zapc

my question was is the main fan supposed to come on immediately when I turn on Ac? if I pull one of the inline pressure sensors on the low side (the smaller one) the main fan comes on immediately, thinking that sensor is bad

vader86

If the AC is turned on, no the fan does not immediately come on, its going to turn on and off based on the pressure.

zapc

thank you,

if you read most of the threads for the last several years most keep saying that is does, i didnt think it did

GREGGPENN

I intended that my first sentence would answer your question. I was trying to convey the fan is not forced on (due to water temp) until 225 -- even with the A/C on.

I apologize for not being more clear.

However, I believe there are circumstances where the high-pressure switch kicks the main fan on/off BELOW 225, but the fan isn't ALWAYS on BELOW 225 when the A/C is running. In fact, it shouldn't NEED to run most of the time below 225. (I don't remember for sure, but I'm thinking the high-pressure switch serves as a psuedo-stat for condensor pressure/temp. Even if water temp isn't high enough, there still might be a need for more airflow through the condenser.)

For the best (definitive) clarification on A/C operation, head posts by SUNCR. I've never seen anyone post more thorough information on our A/C systems.

Of course, the internet likely provides general A/C theory if you want to learn it.


Oh yeah....So you know, the main fan kicks OFF when the car is moving fast enough. IIRC, the turn-off speed is around 11mph.

zapc

thanks again

gerardvg

Hi

The a/c cooling fan request switch had a small round plug, is located on the a/c line next to the high pressure cut out switch that has two spade terminals.

The pressure switch will signal the ECM to request the cooling fan turns on and will cycle on and off, the switch opens at 230psi and closes at 180psi.

The fan will not come on instantly when turning the a/c on, it will take a few seconds to build the pressure depending on rpm of course.

Hope it clears up the a/c and cooling fan operation.