2 Radiator fans??

[benzsel]

I have a 91 420 sel -- There are 2 small fans on the outside of the radiator-Even in hot weather neither one of these fans come on.- I was told by a shop that both are for AC and would only come on during AC operation,and that the main engine fan was responsible to cool the engine--Is that so??Can someone explain the operation of these 2 fans. Thanks!!

[johnmci]

On a W140, which doesn't apply in your case? The aux fans are first speed controlled, (that is turn at 2 or 3 different speeds), and second turn on based on A/C pressure and engine temp. So for example on my 93 500SEL they come on based on what the A/C pressure is, or when the temp goes over 105c. If I recall on my w123 300TD again the one aux 2 speed fan turns on based on A/C pressure and/or engine temp.

[wbain]

On page 79/203 of:

http://mb.braingears.com/126_DISC2/program/ETM/126from86.pdf

shows that the coolant temp must be over 105 - 115 deg. F for the fans to come on and that the a/c can also be on and running.

You can now test the fans manually using the schematic.

I hope this helps.

[Brett San Diego]

You can easily modify the circuit to turn the fans on at a lower temp to help reduce engine operating temp.

http://pages.prodigy.net/jforgione/MB_CTS.html

Brett

[benzsel]

I recently bought a 91 420 sel-- And ALL the info i can get the better so again thanks all for your help.

[Conrad]

Welcome to the MBCA S Class Forum. If you are not already an MBCA member, I heartily invite you to join. Check out the home page as you will find numerous benefits that will add to the pleasure of your MB ownership.

Your 420SEL is an example of the very best automotive engineering and styling that was available in 1991. It remains a classic example of excellence in design and performance. Join us! :)