Its summer again,time for a cooling question

[latief]

I have read and searched....so i know that it is normal for the temp to be around 100 in a hot day at idle with ac on.....

here is what i noticed today since the weather is near 90 degrees here.....

the car usually idles around the 87-90ish without AC. today while driving, it was most around 100 all the time with the AC on, even slightly edging above 100.....here is the interesting thing...with ac on low fan, the Aux fans don't come on immediately, and the heat seems to creep-up above 100 a bit. then both fans come on....with AC on Auto (fan blowing strong), both Aux fans kick in immediately and temp remains around 100 (does not go beyond that)........is this normal? so, the bottom line of my question is that i am not sure what the proper operation of Aux fans should be like...

this is Florida, so no messing around with cooling issues and fans here, it will cost me an engine ....

New water pump, hoses, radiator, fan clutch, thermostat all after the head gasket so i assume i am covered in that regard....

thanks

[JohnM.]

Aux fans turn on at approx 105C. Sounds like your car is operating right where it should be. Since your cooling system seems to be completely new, I think you are covered in that regard.

How is your fan clutch? When you turn the engine off, does the plastic engine fan stop pretty quickly? Or does it free-wheel for an extended amount of time? That is the other main contributor to proper engine temperature in these cars. If the fan clutch does not lock up enough when the engine gets hot, it's not cooling it as efficient as it could be.

[latief]

Fan clutch is also new...i can hear the fan roar when accelerating, and i can tell that is disengages at the higher rpm as it should....

About the aux fans, are both supposed to engage at the exact same time, or does one start before the other one? because i think one of mine starts slightly later especially when the engine is not very hot (such as engaging the ac while engine is still relatively cold)...........

I am going to take them out and clean the contacts and all just to be sure.....

thanks

[latief]

oh, and will a slightly lower than optimum AC charge affect the operation of AUX fans?

Thanks,

[macdrone]

Yes or a bad sensor on the dryer which has 2 switches.

[Cal Learner]

The aux fans are wired in parallel so, if they run at all, they operate together. As macdrone says, it could be a bad high pressure switch on the A/C drier. But it could also be low refrigerant charge, as you asked. The pressure switch on the drier is responsible for low aux fan speed, helping to prevent the temp rising to the point that the high speed kicks on at ~105C in the first place. But that pressure switch monitors pressure buildup in the A/C condenser, and if the refrigerant charge is too low, it will not produce the pressure levels adequate (around 15 bar) to engage the switch to tell the fans to come on low speed. At least, that's how it works in my W124.

[latief]

So this is my analysis of the situation....

Cooling system is functioning normally, the only problem seems to be in one of the fans, and the ac charge...

Since my AC charge is a bit low...I think the pressure is insufficient to kick on the fans on low speed as needed. so i will have to address this problem. AC comes on without the fans, therefore heat goes up and engine tends to be toasty......eventually they do come on on low speed, but they take some time to do so..

I will need to clean and trace the connections on the second fan to see what is going on with it....it occasionally seems to hesitate to come on, so something is not right....even when it comes on, it seems slower than the other one...although i think it is a connection issue since it works fine most of the time....and when it is not working, pushing it, tapping it, spinning it does not make it work so maybe it is not getting power...?

what do you guys think?

thanks for the responses, and thanks Macdrone for replying on the other forum also

[PETERPNYC]

Originally Posted by Cal Learner

The aux fans are wired in parallel so, if they run at all, they operate together. As macdrone says, it could be a bad high pressure switch on the A/C drier. But it could also be low refrigerant charge, as you asked. The pressure switch on the drier is responsible for low aux fan speed, helping to prevent the temp rising to the point that the high speed kicks on at ~105C in the first place. But that pressure switch monitors pressure buildup in the A/C condenser, and if the refrigerant charge is too low, it will not produce the pressure levels adequate (around 15 bar) to engage the switch to tell the fans to come on low speed. At least, that's how it works in my W124.

I had metioned in another post that at the end of last summer my a/c had run out of coolant R134A . Since I changed evap/all in 2004 I figured this was a very slow leak. I hope 6 years is fairly normal or at least acceptable ?

When my Indy went to fill it last year he ran out of R 134a at 1lb in my system . Now when I use K6JRfs diagnostic methods I get as high as
13-14 bar on postition 7 (which measure bar) with outside temp at about 70 F.

I dont know how high that should go . What should it be when full of R134 under warm conditions and using a/c at high fan ?

I am leaving for Greece for 3 months and my new Indy was out of gas and suggested I fiill it with a can from an auto store.

I noticed fans come on high when temp get over 100 or so and now thanks to you I know they should also come on low, but do not because I am low on R134a. My question is can I do damage to the a/c driving it like this for the next 6 days and the first few days in July when I get back .

I would prefer not to use the canned stuff and have it properly filled when I get back

[latief]

So upon further testing, I removed the connector on the water pump. both fans come on strong. I then jumper-ed the connection on the pressure switch, both fans came on slow..so either my AC pressure is low (which i know it is), or the pressure switch is faulty...

What should be the correct pressure reading for the AC system on high and low ports for my car? and how to eliminate the pressure switch as a problem ?

thanks,

[latief]

FIXED!!!

Recharged the AC, Fans first speed comes on as it should, no over heating.......

Thanks guys !! i will further test and update if anything changes

[macdrone]

Low speed is engine temp so thats weird freon charge fixed that. A/C should be high fan speed when engaged. Also if you can opt for a new radiator and new thermostat I would do it.

Made a huge difference in cooling in my ride.

[Cal Learner]

Originally Posted by macdrone

Low speed is engine temp so thats weird freon charge fixed that. A/C should be high fan speed when engaged. Also if you can opt for a new radiator and new thermostat I would do it.

Made a huge difference in cooling in my ride.

No, I think you've got that reversed. Low aux fan is triggered by the pressure switch on the receiver/drier, while hi speed is triggered by the thermistor on the coolant pump (or on the head in earlier models).