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  #1  
Old 02-18-2003, 02:33 PM
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603 Auxilliary Cooling Fan Operation/Troubleshooting?

I have the MB factory W126 Maintenance manual but can't find any reference to the auxilliary cooling fan operation. Is this info there? If so where?

I found a temp sensor on the front of the engine that causes the high speed auxilliary fans to kick in. Does anyone know at what temp it is suppossed to trigger the fans?

Thank you.
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Old 02-18-2003, 03:29 PM
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Try the ACC section of the manual.

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Old 02-18-2003, 04:30 PM
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sixto,

By ACC do you mean Air Conditioning? I looked there and didn't see it?

Thank you.
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Old 02-18-2003, 05:00 PM
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There's a bit of a diagram on page 9 of the ACCfrom86.pdf file in the ETM folder. Doesn't say much.

There's more on page 81 of the 126from86.pdf file in the same folder.

Those are pdf file page numbers, not document page numbers.

My interpretation is:

- Fan turns gets power through a preresistor (low speed?) when the AC system is sufficiently pressurized (compressor is operating properly)

- Fan turns gets power bypassing the preresistor (high speed?) when the engine temp gets to 105C.

- AC compressor clutch loses power when the engine temp gets to 115C.

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Old 02-18-2003, 08:29 PM
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Sixto is correct, that is how the system operates. The one switch is a 3-prong widget on top of the water neck, near where the upper radiator hose connects to the engine. It is the 105/115C temp switch.

The other (low-speed) switch is at the receiver/drier, stock was a green 16/20 bar switch which made the fan almost never run, it was later replaced with a red 12/16 bar switch that improves AC performance by running the fan at low temp more often. The 105/115 switch should almost NEVER need to do anything as these cars with properly working cooling systems almost NEVER get above 105C...


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