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Old 05-05-2003, 10:15 AM
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Join Date: Jul 2002
Location: Dallas
Posts: 330
TIps to save A/C system

With summer coming up and Texas heat already threatening, I'm starting to fear A/C system failure of any kind. Epecially the evaporator. Does anyone have tips on system-saving? I like to turn my A/C off just before I reach my destination to allow the system to circulate some warm outside air through. Also, I don't like to leave the A/C on when I crank the car. I don't know if either of these little efforts help in the least.
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Old 05-05-2003, 10:25 AM
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Join Date: Mar 2003
Location: Convent Station, NJ
Posts: 755
I've always been told to run your AC once or twice a month regardless of the season. This is to keep the seals from drying out.

'85 380 SL (sold)
'85 Carrera Flatnose
'71 280 SL Signal Red/Cognac
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Old 05-05-2003, 10:46 AM
Posts: n/a
Rick has offered about the only tip you need, and actually on your car that is more or less automatically taken care of as is everything else on your particular model.

The automatic climate control system does not engage the compressor after start up until after a short delay that is there to ensure that oil pressure is present prior to clutch engagement.

The ACC also will kick in the compressor occasionally in our winter climate which satisfisfies the need to turn the compressor to keep the seal lubed.

There is really nothing you can do except set you ACC temp wheel where you like, punch the middle button of the control unit and press the auto fan button. Once this is done just forget it until it doesn't cool any longer.

There is really no preventive maintenance that you can do or that is required.

I cross my fingers every spring hoping that my difficult to change evaporator on my 124 car has yet to spring a leak.

Good luck,
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Old 05-05-2003, 11:03 AM
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Join Date: Jun 2001
Location: San Francisco, CA
Posts: 3,096

Do you ever clean the radiator area on your cars? For an example, using a hose to flush out bugs from the engine side out?

'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)
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Old 05-05-2003, 11:14 AM
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Join Date: Jun 2000
Location: Plano, TX
Posts: 2,476
Not so much preventative, but I do have a tip. Insure the electric cooling fans in front of the condenser are operating as intended. If the fans fail for some reason, the a/c will still work fine while moving, will work quite poorly while stopped. The lack of airflow while stopped will cause much higher pressures inside the system, as heat is not being removed. (Remember pv=nrt from high school?) This will stress the compressor, manifold hoses, condenser, and of course the o-rings in the system. Eventually the entire system will fail. Sometimes an o-ring gives up the ghost, releasing the refrigerant charge. Sometimes the front seal on the compressor begins leaking, which can result in eventaul seizing of the compressor.

Anyways, on a warm day the electric fans should run at low speed (or cycle on and off) after a bit of stop-and-go driving.

- JimY
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Old 05-05-2003, 11:33 AM
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Join Date: Apr 2002
Location: westchester, ny
Posts: 747
On my '87 300e, the electric fan began to run as soon as I started the car, so I have disconnected the wires. Do you know what would be the likely cause of them running non-stop? Thanks
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Old 05-05-2003, 02:07 PM
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Join Date: Jul 2002
Location: Dallas
Posts: 330

There is a switch on the drier that senses pressure in the system and turns on the fan. Maybe it has gone bad. The part is $25 on line and $50 at the dealer. The system has to be evacuated to replace. Could this be your culprit?

Last edited by 95E320cab; 05-05-2003 at 02:31 PM.
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Old 05-05-2003, 02:11 PM
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Join Date: Apr 2002
Location: westchester, ny
Posts: 747
Maybe that's why the prior owner rewired it so the fan would always run, so he wouldn't have to evacuate the system since he had recently done an r-134 conversion. I'll look into this, thanks.
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Old 05-05-2003, 02:48 PM
Posts: n/a
Cleaning bugs and other debris from the front of the car including condensor is standard preventive maintenance as far as I'm concerned. This is done on my cars as standard maintenance, not specific to maintenance of the a/c.

Have a great day,
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Old 05-05-2003, 05:01 PM
I told you so!
Join Date: Jun 2002
Location: Motor City, MI
Posts: 2,741
Protect the condenser from road debris impact

There is one thing I stress to most people about extending the life of their a/c.... put a screen in front of the condenser to catch any rocks or debris before they hit the delicate tubes! This can go a long way in putting off a potentially expensive repair. The same type of damage that chips your windshield can poke a hole in your condenser -- and the condenser is closer to the ground than your windshield. I use 1/2" hardware cloth and stand it off at least an inch from the condenser. This shouldn't reduce much air flow.

Of course this tip doesn't apply to all cars, but I thought I'd pass it on to the people that own cars where the grille is too "open", leaving the condenser prone to damage. This is one condition I can call a manufacturing deficiency.
95 E320 Cabriolet, 131K
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