Electric Fan ...
5 June 2019
For this project I've decided to use an electric fan ... why? First of all the visco fan needs power and there wasn't enough space for it behind the radiator.
So after finding a condensator for the aircon, I measured the front and found out, that the maximum fan size is 16". I also wanted to have a continious fan speed control, not just "I switch it on, because it is too hot".
I got a Derale fan with their control unit*. This control unit also provides an override switch; so in case the control unit doesn't work, you can press a button and the fan runs. I will redesign an original W126 "interior light switch", so I can manually operate the fan from the centre console.
The brackets on the photo look like "original Mercedes" I was told. But it is not. We just wanted it to look like that. So I went to a hardware store and got a steel pipe with the original diametre. Then we took a 16" rim, put it on a tyre balancing machine and bent the pipe in an exact 16" diametre ;-) ... flattened the ends and - voilà - the holders were done!
* For your reference: I used a Derale 16'' Tornado Electric Puller Fan (16516) and a "PWM Fan Controller" (16795)
Final installation ...
10 October 2021
This picture shows the final installation. Reverted back to the old "probe style" sensor, which is stuck through the radiator.
The following measures have been additionally taken to be able to cool that huge motor in that narrow body:
- Wrapping of the manifolds and downpipes with a special band (from motorsport); this absorbs roughly 75% of the hear there
- Modified original W115 shroud installed inside to direct more air towards the motor
- The starting temperature for the fan control unit is set lower to 71°C (standard 82°C), as the "real" motor temperature is relevant and not the sensor temperature (found out by experiment)
- A special rubber lip is put between the cross bracket and the radiator, as a lot of air was lost there
Fine Tuning Sensor ...
22 July 2022
Probably quite usual in such conversions is a lot of little bits of fine tuning. By accident I saw, that the stick-on sensor for the electric fan got loose as it was only held by a plastic clamp.
After checking with the manufacturer (Derale), I cut an M5 thread on the sensor (luckily the Americans used metric measurements ;-) ) and I could fix the sensor with a nut. Next 1,500kms will show, if it works!