W124 manual fan switch - PeachParts Mercedes-Benz Forum

cheatman · #1 04-21-2010, 08:28 PM

Hello. My father has a 1990 W124 200E (same as mine). During the summer, he often is in tailback, so the temperature goes up to about 100°C and the temperature sensor turns on the fan through a relay.
I would like to install an "override" switch, so that he can manually turn on the fan, even if the temperature limit hasn't reached.
I think I should install the switch to provide a +12V, or a ground, or a short, to a specific point of the electrical system.
I didn't understand if that fan is the "auxiliary fan" mentioned in the car electrical schematics...
Any advice?
cheatman

Spetz · #2 04-22-2010, 09:15 AM

From what I have researched, if you join these two wires together, the fan will go on:

Do not quote me on this, I have another thread called "Fan not coming on" and through that someone told me this is how to test if the fan is not working because of low AC gas pressure.
I posted a question asking if those are the right wires, and if they are I assume you could have a wire or relay connecting to a button for on/off

Spetz · #3 04-22-2010, 09:34 AM

To correct myself, it seems it is the brown wires to the left which have to be connected for the fan to come on

cheatman · #4 04-22-2010, 05:05 PM

I can't find that connector!

This car has a M102 motor.
Notes: the air intake hose is disconnected because the car has been converted to CNG. It's normal. That Landi thing is the CNG control unit.
Can you help me finding the right connector for the temperature sensor?

Clickable thumbnails:

macdrone · #5 04-22-2010, 05:08 PM

first photo, under the abs deal is the dryer with your connectors on it.

macdrone · #6 04-22-2010, 05:09 PM

It looks just a little different then the other guys photos because his is a newer car i think. The dryer changes year to year kinda sometimes.

cheatman · #7 04-22-2010, 05:13 PM

That connector has 4 wires. I have to take another photo to check. Back in 2 minutes!

Is this the right connector?
That piece has the manufacturer signature "Autogi". It's an Italian company, it's in the category "air conditioners for cars".

cheatman · #8 04-22-2010, 06:16 PM

Given that it's a part of air conditioner circuit, I don't think it's the right sensor. My car (same 200E but without air conditioner) doesn't have that light gray tube neither that connector.
I'm searching for the temperature sensor that turns on the fan. I think it's near the motor.

Cal Learner · #9 04-23-2010, 06:47 AM

Not familiar with the 102 motor, but if your car doesn't have air conditioning, no need to be looking for a drier with the 4-wire pigtails. That's a pressure switch in any case, not a temperature switch (at least it is on a M103 motor). There is a temperature sensor that triggers aux fan when the coolant temp reaches about 105C, and that may be located on the head or possibly on the water pump/thermostat housing. On a 103 motor, it has a blue base with a 2-wire connector. On a 103 motor, if you pull off the connector with key on, engine off, the fan should come on. It's an easy test for the fan function, and may help you identify which sensor you're looking for.

As for installing a manual switch, search on this forum. Arthur Dalton has repeatedly described that very thing, particularly for guys who tow trailers and put higher thermal loads on their motors. HTH

cheatman · #10 04-23-2010, 08:34 AM

I took some photos near the oil cap. Here are some connectors.....
I try making a short on the 2-pin connector that is on the 2nd picture, but the fan didn't turn on (I also turned on the engine).
The last picture shows a 1-pin connector placed on the right side of that metal thing in the center of the first picture.

Any hint?

cheatman · #11 04-23-2010, 01:37 PM

Quote:

M102 powered models:
These have an engine driven fan with an electromagnetically coupled clutch. Until the coolant temperature reaches 105 degrees C the fan is not coupled and is effectively stationary (will turn very slowly due to air moving through radiator due to forward movement of the car). Should the coolant temperature reach 105 degrees (very likely in traffic due to little air movement through radiator) the temperature switch will activate the electromagnetic clutch and the fan will rotate at a speed proportional to engine speed (without any "slip" as would occur with a viscous clutch coupled fan). When the coolant temperature drops back to around 95 degrees the clutch will release. In cars with air-conditioning, the electromagnetic clutch will also engage on demand of the air-conditioner's pressure switch at the receiver-dryer. The air-conditioner pressure switch will also activate the auxilliary fan in front of the condenser at low speed (low speed results from the fan being supplied via the series ballast resistor). Should the coolant temperature rise to 110 degrees the temperature switch will activate the auxilliary fan at high speed.

I have got air conditioner, but rather than air conditioner sensor, I'd want to connect to an engine temperature sensor and jumper it to activate the fan located between the motor and the radiator.

@Spetz: On your car, that's the right connector. Have a look at the last figure on http://www.w124performance.com/service/w124CD1/Program/Engine/602_603/20-330.pdf

cheatman · #12 04-23-2010, 04:40 PM

Here are other pictures of the zone near the ABS unit.

cheatman · #13 04-23-2010, 06:41 PM

Pictures of the car & fans.
I want to turn on the big gray fan pointed by the red arrow.