My '97 S500 seems to do an O.K. job cooling down the intrrior. (The car is Black on Black) It's not mind freezing cold but does the job given enough time. The two aux fans seem to cycle on for about 15 seconds and off for about 30 then continue this indefinetly. This is done in the driveway with a cool motor and an OAT of about 78. I'm fairly new to the car but it was my understanding that the aux fans will kick on anytime the compresor is on assuming a pressure switch dosen't kill the fans due to low freon. Am I just being picky and anal or could my freon level be falling. Also, I plan to go out and buy and temp gauge that I could stick in one of the air registers. What temp should I find? I'm guessing around 45. Any insight will be of great help.

Thanks,
Paul

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Paul Hansen

1997 S500 (100,000mi)

Duct temp varies with humidity & pressure & outside temp! OF course it will also vary with blower speed!

At low blower with 20%-40% humidy & temps around 75-80 you can expect 45 deg comming out of the duct!

You need to check the system pressure as the aux fans SHOULD run longer the warmer the outside temp.

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Check out MENU#16 for temp/pressure chart showing typical values. A temp gauge stuck in the center opening will give a close-enough temps to compare.

You can also 'see' the pressure in the compressor from MENU#15. Follow the procedure for "Operational Checks". The evap temp is #5; pressure is #7

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Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

Thanks Jim- I've always admired your web site and appreciate your participation on these forums!


I think I might have been a bit hasty- the center vent temp settles out at around 42 degress with an abmient OAT of around 80 or so. I think it has more to do with the big black car and black interrior syndrome.

I'm still a bit perplexed by the constant cycling of the aux fans though. They're more like 5 seconds on- 15 seconds off- over and over.

PS Does the same procedure in menu #15 apply to the later model ACC?
Thanks again!
Paul Hansen

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Paul Hansen

1997 S500 (100,000mi)

The procedure is good up to 8/95. From 9/95, it was changed abit.

Here's for '95 and on:
- Ignition: Pos 1
- Press the AUTO button
- Set BOTH TEMPERATURE selector wheels to 72 degs
- Press the REST button for more than 5 secs
- The left display will alternately show a "1" and the IN-CAR temperature
- Press the AUTO button and the next component number and its value is displayed
- Press REST button to end the test program.

As far as the fans cycling; look at Menu#18 and find the blue chart in the middle of the page: when the pressure gets to a certain point the fans will come on. 1st stage, 14 bar; 17, 2nd stage, etc.

They are supposed to do that.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

Thanks again, Jim!
Happy Motoring,

__________________
Paul Hansen

1997 S500 (100,000mi)