>>300SL Auxillery fans/switch 1990 300SL - Mercedes-Benz Forum

LinkBack Thread Tools Display Modes
post #1 of 3 (permalink) Old 09-15-2008, 05:30 PM Thread Starter
BenzWorld Newbie
Date registered: Sep 2008
Posts: 2
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
(Thread Starter)
>>300SL Auxillery fans/switch 1990 300SL

So my car gets hot and has had issues since I got it. (1990 300sl). The auxillery fans stopped working and a switch was replaced but they keep stop working. Does anyone know where this switch is and is there a way to bypass the fant switch sensor with a direct on off switch-tap into the wire and send either current or ground to activate the relay...any help is appreciated please post here OR get back at me at timeforsound at Yahoo dot com.
zintcat is offline  
Sponsored Links
post #2 of 3 (permalink) Old 04-10-2012, 05:38 PM
BenzWorld Junior Member
Katila66's Avatar
Date registered: Apr 2012
Vehicle: 1990 300SL
Location: Colorado USA
Posts: 20
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Smile You can easily bypass this sensor

I have the same issue on my 300SL. When I killed my entire cooling system with the wrong antifreeze, I found that my fans were not engaging either. I went through a lot of searching to find what I thought was the correct sensor/switch and am still unsure I got the right one. My Merc spec says it may not be the sensor at all but could be anything along that wiring, even with the working bypass.

It's easy enough to bypass the sensor as I did so that fans stay on whenever the key is on but that's not really very good for the fans to be on all the time. I did discover that without the bypass, the fans work properly as long as the cooling/heating is on. So you can set the temp and just leave it on Automatic setting all the time and it should kick the fans on and off. (The A/C will not work if the sensor is bypassed) Just unplug the wires from the sensor and connect the bypass (a wire with an alligator clip at each end) to each of the wires and it will cause the fans to work with the key. You can wire the bypass to a kill switch inside the car if you want, but for me it's not worth it. I'll just leave the climate control on auto.
Katila66 is offline  
post #3 of 3 (permalink) Old 04-13-2012, 04:56 AM
Outstanding Contributor
eric242340's Avatar
Date registered: May 2007
Vehicle: Zotye Auto 1.5T T600 2016
Location: The wild west of the Far East
Posts: 52,075
Mentioned: 3 Post(s)
Quoted: 283 Post(s)
Welcome to Benzworld


"I am enclosing two tickets to the first night of my new play; bring a friend, if you have one."
- George Bernard Shaw to Winston Churchill.

"Cannot possibly attend first night, will attend second ... if there is one."
- Winston Churchill, in response.
eric242340 is offline  
Sponsored Links

  Mercedes-Benz Forum > General Mercedes-Benz Forums > General Mercedes-Benz

Quick Reply

Register Now

In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode

    Similar Threads
    Topic Author Forum Replies Last Post
    1990 300sl ShouldI? R129 SL-Class 7 03-08-2007 09:52 AM
    1990 300SL amplifier location??? rcltrh R129 SL-Class 5 05-28-2006 12:22 AM
    1990 300SL vs 500SL DougiD R129 SL-Class 5 06-07-2005 03:28 AM
    1990 300SL Burt R129 SL-Class 0 03-21-2004 06:27 PM

    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On


    Title goes here

    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome