A/C refilled, and water temperature seems a bit high - PeachParts Mercedes-Benz Forum

hk20000 · #1 04-07-2007, 02:06 AM

hey guys.

Summer is coming along nicely and I went to refill up my A/C system (it blew only a bit cool before) and it blows cold now... but during the mechanic pumping in the freon I see the water temperature climb to 100C and stays there.

it's kind of scary to look at the gauge although the redline is 120C.....

he was only idling the car and occasionally running the revs up to about 1500rpm to pump the freon around.... the A/C was pumping nothing cold when the water temp is at 100C as well....

I drove it out of the lot and did some quick sprint around hitting 100km/h and the water temp falls back to like 80 or so and the cold air started coming in with A/C put at "LO" and "Auto"

is this normal phenomenon? Another worrying thing is the A/C fan does not run at 100C it starts running quite a few minutes after the water temp is at 100C...... is there anything wrong with my A/C fan thermostat?

car is a 1995 C220 w/ 215000km btw.

stevebfl · #2 04-07-2007, 09:01 AM

The Aux fan comes on due to engine temps somewhere above 100 C for engine temp. It comes on for AC when system pressure gets above about 290psi. Nothing in your description indicates a problem to me.

If your coolant temp is registering higher than you have experienced then it is something to watch out for even if it falls within accepted ranges as it seems to be.

hk20000 · #3 04-07-2007, 11:10 PM

so when I drive the car whether the A/C is on or not seems have great impact to water temp.

no A/C - running car keeps temp at 80C, stopping the car for a while makes it hit about 90C but no more

A/C on - running car temp is at 90C already, stopping the car at the lights will cause the water temp to creep up to 100C and then when you move along with some wind it'll cool back down but only to 90C level.

is A/C that much load to the cooling system???

stevebfl · #4 04-07-2007, 11:27 PM

Do you know how AC works? Using a manipulation of the latent heat of vaporization heat is removed from one heat exchanger (the evaporator in the dash) and moved to the other heat exchanger (the condenser - directly in front of the radiator).

So when the AC is cranking air that is expected to cool the radiator is first ran through a condenser which could possibly be over 300 degrees. Do you suppose that air is a little warmer when it hits the radiator than it would be if no AC action was taking place.

blackmercedes · #5 04-08-2007, 10:56 AM

I know on my 98 C230, when the AC is working hard, it is normal for the coolant temp to be at about 100C or so when sitting in traffic. Has always done that.

So, when you reactivated the AC system, it put increased load on the coolong system, hence you increase in coolant temps.

BTW, and the reason for my post, is I was wondering if you had found the leak of refrigerant for the AC system?

hk20000 · #6 04-08-2007, 04:43 PM

I don't think it's leaking it's 12 years old car with no maintenance records on it it probably just disappeared throughout the years.

I always thought the condenser is behind the radiator not in front? I guess I was wrong.

so the condenser could heat up the air to like 300C?? wow I could fry eggs with that temp....

Does your A/C still manage to blow cold if the water temp is sat at 100C?? Coz my A/C isn't doing much if the water temp is hot....It's working but in a significantly weaker way.

just-n-time · #7 04-09-2007, 03:04 PM

My concern in this mater is the gauge readings,what are they? It sounds to me as though you may be just a little light on your coolant charge. I say this because of the drop in cool air flow at idle or stopped at a light! JNT