W201 aux fans won't turn off - Page 2 - PeachParts Mercedes-Benz Forum

lsmalley · #16 03-21-2013, 03:17 PM

I have the r134. Yes, I will fix it, but is there any harm in disconnecting the switch?

MBeige · #17 03-21-2013, 03:42 PM

The A/C refrigerant pressure sensor prevents the A/C system from operating when an excessively high or low pressure condition exists. Basically it ensures that pressures are maintained between the specified range, and protects the compressor - if the pressure is too low or too high, the compressor can get damaged.

With R134a, you'll need much higher pressures to achieve the same cooling effect as with using R12.

Gilly · #18 03-21-2013, 03:45 PM

Well to say it "protects" the system might be a stretch, I mean sure if the pressure keeps building and building something will blow out, probably a hose or compressor seals, but in the common sense, what it is there for is to keep the AC blowing cool air, it helps the heat exchange through the condensor so the vent temps will lower. So no, IMO there is no "danger" in disabling the low speed fan circuit, maybe in "danger" of having lousy AC performance is all, but again when the temps get hot you can reconnect whatever you decide to disconnect.
When the car is moving, I believe I heard 15mph or so, the aux fan isn't even neccesary, the air is moving through the condensor faster than the aux fan provides. It really is only beneficial when stopped in traffic.
I would consider the high speed circuit much more important than the low speed circuit, that system is there to keep the engine from overheating.

lsmalley · #19 03-21-2013, 04:14 PM

You have all provided great insight. I have even received a PM from Arthur Dalton and he suggests a manual switch inside the cabin which actually sounds like a great idea to me. I'm gonna research adding a manual switch to control the fans. If anyone has the link or knowledge to do this, please let me know.

lsmalley · #20 03-24-2013, 06:45 AM

manual fan installed.

suginami · #21 03-24-2013, 12:38 PM

That's a good move. I put a manual switch in my 280SE 4.5, and I hit the switch as needed.

lsmalley · #22 03-25-2013, 07:02 PM

Will this technique also work to have the high speed fans turn on?

Gilly · #23 03-25-2013, 08:11 PM

I think so, you would just jump the high speed relay instead of the low speed relay. Not sure what happens if you switch them both on, pretty sure it won't go any faster than high speed, but not sure if it would damage the low speed relay or resistor. Would make sure that the temp sensor will still be able to switch on the high speed fan in case someone else is driving and doesn't notice the temp gauge climbing.

lsmalley · #24 03-25-2013, 09:36 PM

Just got a diagram from Arthur Dalton that has a 3 way control switch for low speed, high speed, and factory settings! Gonna look into that. I was asking about high speed, because I live in the desert and in about another month or so the average temp outside will be 105*F-112*F so even with the low speeds on, the car temp gauge will still rise to the point where the high speeds will turn on. Typically in stop & go traffic, but not usually when I'm in motion 30-40 mph, maybe less

Gilly · #25 03-26-2013, 04:46 PM

Right, I'd be sure to shut the aux switch to off when moving over 25-30 mph or so. The air will move through faster than the fan is adding to the flow.

trooper6 · #26 09-03-2017, 12:39 PM

Quote:

Originally Posted by lsmalley

Just got a diagram from Arthur Dalton that has a 3 way control switch for low speed, high speed, and factory settings! Gonna look into that. I was asking about high speed, because I live in the desert and in about another month or so the average temp outside will be 105*F-112*F so even with the low speeds on, the car temp gauge will still rise to the point where the high speeds will turn on. Typically in stop & go traffic, but not usually when I'm in motion 30-40 mph, maybe less

Same issues and I have replaced all relays, resistors, drier and associated switches. I have also tested the Aux fans with 12V and they work. Next is to trace the wiring from the aux fan connect back.

Can you send me the fan schematic that you used for the manual switch. I might have to go that route.