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#1
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w124 Aux fans
Guys,
When I run my a/c, that aux fans do not come on. Are the switched by pressure or freon temp? Thanks!
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RRGrassi 70's Southern Pacific #5608 Fairmont A-4 MOW car 13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete. 99 W210 E300 TD Turbo, chipped. Still needs EGR Delete, 228K 90 Dodge D250 5.9 Cummins/5 speed. 400K |
#2
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The a/c aux fans on your car work by means of a pressure switch that is on the "high" side of the system next to the drier.
It should close at 16 bar (240 psi) and then open at 12 bar (180 psi). The pressure switch activates a relay in the fuse box which then sends power through a resistor (to give slow speed) and then to the fans. I would start by rotating the fuses in their holders (to remove possible corrosion) and if you still have aluminum fuses then I would recommend upgrading them to the newer style that don't corrode. Fuse 7 does the switch and Fuse D is power to the fans Of course your system may not be getting to a high enough pressure in the first place. |
#3
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Ok, so it is pressure. Thanks for the info. I am using Duracool. Someone did a poor 134 conversion. Added the the suction port fitting, and not the high port. They left the R12 fitting unchanged. Found that out the hard way when trying to attach gauges.
I am going to change the fan operation to when the compressor is engaged, and depending on ambient temp, so that they do not come on during the winter.
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RRGrassi 70's Southern Pacific #5608 Fairmont A-4 MOW car 13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete. 99 W210 E300 TD Turbo, chipped. Still needs EGR Delete, 228K 90 Dodge D250 5.9 Cummins/5 speed. 400K |
#4
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Quote:
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#5
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True, but when stopped at a long traffic light, or is stop and go traffic, I think they are needed.
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RRGrassi 70's Southern Pacific #5608 Fairmont A-4 MOW car 13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete. 99 W210 E300 TD Turbo, chipped. Still needs EGR Delete, 228K 90 Dodge D250 5.9 Cummins/5 speed. 400K |
#6
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So let the pressure switch turn them on when they're needed. As Chris said, if your fan clutch is doing anything, they're only in use on hot days or extended standing. The refrigerant needs some heat in it to do work, if you overcool the condenser, you will have very poor A/C performance on moderate or cooler days. There is no better way to control the fans than the refrigerant pressure.
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Current stable: 1995 E320 149K (Nancy) 1983 500SL 120K (SLoL) Black Sheep: 1985 524TD 167K (TotalDumpster™) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!) |
#7
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At what pressure are they supposed to activate?
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RRGrassi 70's Southern Pacific #5608 Fairmont A-4 MOW car 13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete. 99 W210 E300 TD Turbo, chipped. Still needs EGR Delete, 228K 90 Dodge D250 5.9 Cummins/5 speed. 400K |
#8
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Sure if you live somewhere where the climate is cooler. I find that the clutch fan no matter what brand is flat out useless. The electric fans do almost 100 percent of the cooling for me and all the Mercedes I’ve owned
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1993 e300 1995 e320 1994 e320 2006 s500 4matic 2004 Jeep wj overland 2001 Ducati 748 2004 Honda shadow aero |
#9
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Chris provided the answer in an earlier post:
"It should close at 16 bar (240 psi) and then open at 12 bar (180 psi)." Note that the pressure switch switch could be bad, likely if original, and if you change it, you will need to evacuate/refill the refrigerant. Since you are opening it up and if the dryer is old, may as well replace that too, they are not expensive. FWIW, after redoing my AC system, the aux fan come on in Low speed whenever the AC is activated, goes to high speed based on the pressure/temp increases as needed.
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Stable Mates: 1987 300TD 310K mi (Hans) 2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee) |
#10
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The electric fans move a tiny fraction of the air that the clutch fan does. They are there solely to assist the A/C condenser and act as an emergency backup when your clutched fan packs up. When working correctly, the clutched fan moves a hurricane's worth of air through the radiator and condenser. Stop buying cheap fan clutches or pulling from junkyard cars.
__________________
Current stable: 1995 E320 149K (Nancy) 1983 500SL 120K (SLoL) Black Sheep: 1985 524TD 167K (TotalDumpster™) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!) |
#11
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Additionally, high speed is not triggered by the refrigerant circuit. Earlier cars have a temperature switch somewhere in the cooling system (location varies with engine) that triggers the high speed relay. Later cars have a temperature sensor in the cooling system that feeds the climate control unit to accomplish the same task. High speed fan is always a function of coolant temperature, not refrigerant temperature/pressure. This isn't a great way to trigger high speed fan operation since your engine is running hot and you have a 5-10˚ window before the compressor is disabled due to high temp.
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Current stable: 1995 E320 149K (Nancy) 1983 500SL 120K (SLoL) Black Sheep: 1985 524TD 167K (TotalDumpster™) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!) |
#12
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Quote:
The clutch fan is a garbage solution for the om603/m103/m104. There's not enough room between the engine and radiator to fit a vicous clutch fan large enough to do the job. The less powerful om602 was fitters with a much larger fan (wider blades) than the om603.
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CENSORED due to not family friendly words |
#13
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Quote:
Fun fact: The metal alloy fan on the 603's is the exact same part number as the V8. Funny how they don't overheat either.
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Current stable: 1995 E320 149K (Nancy) 1983 500SL 120K (SLoL) Black Sheep: 1985 524TD 167K (TotalDumpster™) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!) |
#14
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Quote:
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CENSORED due to not family friendly words |
#15
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As per Mbz FSM. The pressure switch is 15bar off 20bar on. Or 217.5psi 290 psi.
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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed. W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html 1 X 2006 CDI 1 x 87 300SDL 1 x 87 300D 1 x 87 300TDT wagon 1 x 83 300D 1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry. |
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