Main.TrailIndexPage | Electrical Systems | Electrical.Heating | Replacing Heater Leavers

Procedure to Replace Heater/Air Control Levers

(Originally done on a 1971 280SL).

Part of Heater System and Heater Levers.

The 230 SL Service Bulletin for this procedure is a useful guide for all models.

Remove the following items:

  1. Glove Box
  2. Clock
  3. Blower Switch
  4. Radio
  5. Cigar Lighter

Cigar Lighter

Remove the Cigar Lighter according to the instructions in that section.

Chrome trim

Next is the removal of the chrome trim surround. There are 3 pieces to this surround (right, center and left). Each piece is held in place with a 10 mm nut on the rear (refer to pictures). It’s best to start with the center piece, then the right, then left. Once the nuts are removed, the left and right side are removed by pulling them forward and then by sliding them out. Right side slides out from the right, left from the left. This allows for clearing the lever buttons.

This picture shows the center and right chrome trim removed.

This picture shows all 3 chrome trim pieces removed

This picture shows the back of the center chrome trim, with 10 mm nut

This picture shows the back of the right side chrome trim, with 10 mm nut.

This picture shows the chrome trim removed. Note the notches in the dash. These are needed to clear the lever buttons when removing & reinstalling the control unit.

Disconnecting the control unit

The next step is to disconnect the 4 cables that connect to the control unit. The procedure starts with the removal of the bottom right side, then the bottom left side. To remove the cable(s), you first “pop off” the metal clip that holds the cable to the control unit. This picture shows a close-up of metal clip for the top left side. You can use a small flat-head screw driver to pop off the clips. Be careful! The clips are under tension and will pop off.

This picture shows a close-up of the metal clip (control unit out of the car and on the bench). The clips are removed and reinstalled from the side. The clip needs to be re-installed with the small grooved tooth on the top, flat side on the bottom. The small grooved tooth assists with pushing down on the cable and holding it in place in the control unit.

This picture shows a close-up of the upper and lower left side cables. Note the small bend in the cables. This bend is where the cable(s) rest against the holes in each of the screws that reside in each of the plastic control levers.

Another close-up of the cable. The metal band around the cable resides inside the control unit housing and assists with holding the cable(s) in the control unit.

This picture shows the cable connected to the upper left side lever. To remove the cable, unscrew and remove the nut and the washer. Slide each lever to its maximum position (ie. Left levers into the full left position, right to the full right position. Using a small needle nose pier tool, carefully back out the cable from each screw hole.

This picture shows the nut and washer removed, cable still in position. Note bend in cable is resting against the back of the screw. Re-install in same position.

As mentioned earlier, the basic procedure involves removing the lower right cable 1st, then the lower left cable, then the upper right, then upper left.

Before you can remove the upper right & left, you need to carefully back the control unit out of the dash (using the 2 notches in the dash to clear the buttons on the levers). With both bottom cables already disconnected, you begin by backing out the right side, and slightly tilting the unit down as you begin to slide out the upper left side. When both sides are backed out of the dash, carefully lower the control unit down (unit still inside the dash). Next remove the upper right cable, then remove the upper left cable. Unplug the wire for the control unit lights. This is located on the upper left side of the control unit. Lastly, remove the entire control unit out of the dash through the open glove-box hole.

This picture shows the dash apart and control unit out of the car. Our cars sort of look ugly without the dash pieces and fancy chrome trim…..

This picture shows the top side of the control unit removed from the dash. Your unit may look different. The upper left plastic piece on my unit, the piece that plugs the unit into the electrical source was broken. I soldered 2 small wires on my unit to make it easier to plug the unit back in.

This picture shows the bottom side of the control unit. Both the upper side and lower side have caps with screws in them. Unscrew the top screws and remove the caps. Carefully remove the light bulbs with their respective holders (holders held in place with another small screw). Slide off the old top control levers. Next slide off the inside clear cylinder from each side through the bottom. Slide off the bottom levers and replace with new ones. Reverse the above process installing the new upper control levers also.

Note: When reassembling, be careful not to over tighten the screws! The plastic is old and will crack and/or break! Tighten very carefully! Also, prior to sliding on the new levers, you may want to smear a small amount of white lithium grease on the inside of each lever wheel.

This picture shows my secret weapon to making the control cables slide easily. I used a product called PB Blaster and sprayed some into a plastic cup. With the control unit out of the car, I used a small syringe and injected PB Blaster into each cable opening inside the dash. I then carefully moved each cable in and out, ensuring that the cables moved freely and easily. The cables must slide easily or you will end up with broken levers again.

To reassemble, reverse all above steps. Good Luck and remember to have patience. When you are finished, you will have new control levers that work and look great, especially at night when your dash is lit up with really cool colors!

Sometimes cables have accumulated too much dirt and old grease and cleaning them with a syringe as described above is not possible. In those cases this gadget that is available in most bicycle stores can do a better job:

Remember to replace the light bulbs while you have the control unit out of the dash and apart.
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