Main.TrailIndexPage | Electrical Systems | Electrical.Heating | Electrical.Blower


This component is part of Heating System.


Define the component. Include, if known, the german language word for the component, as well as the English or American equivalent. Show a picture, a diagram.

  • Its technical name & common name(s)
  • part # - start year & end year
  • which area it belongs to - engine, transmission, body, injection etc, link back to the relevant section


Describe, in general terms the function of this component. Meaning what is it there for and what role it plays. Describe how it works, the inside mechanism. Use diagrams to explain.


Describe common maintenance procedures, and common faults that may occur. Describe how these may be diagnosed and resolved. Again, include diagrams, photographs and explanations. Where possible, include measures, tolerances, weights etc.

  • Symptoms when it faults
  • How to test if it is faulty - what tools to use
  • How to fix / change

Blower Rotary Switch

A round knob can be turned to adjust the speed of the heater fan. It's called the "blower rotary switch" in the illustrations for Job No. 83-2 which can found in the section about Heater Levers. The blower rotary switch clicks first when you turn the fan on low, then the fan speed increases as you turn the blower rotary switch clockwise, then it clicks again when you get up the max fan speed. Job No. 83-2 includes the procedure for removing the blower rotary switch.

In early models, there was a small "light pipe" which illuminates the centre of the blower rotary switch when the system lights are on and the blower rotary switch is turned on. Illumination is provided by a small bulb inside the back of the blower rotary switch. The bulb gets black inside as it ages, so the light you see at the front of the knob dulls with time and finally the filament burns through and no more light gets at all. You have to get to the back of the switch to pull the bulb. Since it's a time-consuming multi-step process, the suggestion is to take the whole switch out, clean and refresh it. Note that the red bulb in the photo here was painted and is not as original.

Heater Blower Removal, 230SL

1. First remove the glove compartment by removing several screws inside the compartment. The compartment light has two wires hooked to a connector located on the air distribution duct, disconnect these two wires and label them.

2. Then, remove the clock by loosening the two thumb nuts behind the clock, pry off the electrical connector and label it.

3. Next is to remove the radio, there are 2 set screws on the knobs and two nuts on each side. There are two retaining metal brackets that need to be loosened. Remove the radio from the back by sliding it through the glove compartment.

4. With a good working light, you will find the air distribution plastic housing attached to the air ducts and bolted on the blower housing by 4 bolts (10 mm). Two bolts at each side of the housing and two at the center of the housing. Once these bolts are removed, the air distribution housing can be pulled forward away from the blower housing. There are good pictures of the housing that can be used as a guide at:

5. On the right hand side of the air duct, there is a wiper arm that needs to be disconnected. This will enable the air duct to be removed.

6. If you look straight at the upper center of the blower housing, you will see two bolts (10 mm) retaining the blower housing to the car body, remove them. This will free the blower housing from the top.

7. There is one more bolt to be removed. If you look at the center bottom of the blower, you will see an L bracket with two bolts (10 mm) retaining the blower to the bell housing. The bolt goes into the bell housing and has a nut underneath the bell housing. To remove this bolt, remove the carpet from the bell housing. On the right hand side of the bell housing, there is a circular cut out with a cover that is retained by a few screws that need to be removed. You have an easy access to the nut (10 mm), remove it.

8. The blower housing is completely free, wiggle it and pull it to the passenger side, it should slide easily.

9. Once the blower is out, remove the two plastic covers, you will see the wheels. Try to move the wheels back and forth; you may make the blower rotate by hand.

10. To disassemble the blower motor, on each wheel, there are two Allen keys, loosen them and pull the wheels out.

11. The motor is bolted on the housing by nuts, it should be removed easily.
< Electrical.Heating | Main.TrailIndexPage | Electrical.Levers >