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Replacing Your Mercedes-Benz A/C Belt
 
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Pelican Technical Article:

Replacing Your Mercedes-Benz A/C Belt

Steve Vernon

Time:

1 hour1 hr

Tab:

$8

Talent:

*

Tools:

6mm, 8mm Allen, 13mm, 19mm wrench

Applicable Models:

Mercedes-Benz W126 (1981-91)

Parts Required:

New belt

Hot Tip:

Be careful working around your radiator

Performance Gain:

Cool cabin

Complementary Modification:

Top up refrigerant

The Mercedes-Benz W126 has the proud distinction of having 5 different drive belts. This article will show you how to replace the A/C belt.

The nice thing about the A/C belt is that it there is only one belt (the air pump) that you have to remove to get access to the A/C belt. This article will show you how to remove both belts.

The air pump is located on the lower passenger side of the engine.

To remove the belt you will need to loosen the pump itself. Use a 6mm Allen and loosen the Allen bolt at the top of the pump. The pump has a tensioner/locking bolt on its lower housing. There are two nuts on the same bolt. Loosen the outer 13mm nut and then turn the inner 19mm nut. The 19mm has a spiral toothed ring on it that is used to tension the belt. Turn it counter clock wise to loosen the belt and when reinstalling turn it clock wise to tension the belt and while holding the tension tighten down the 13mm bolt.

Don't forget to retighten the 6mm allen bolt when you are done.

With the air pump belt off you can replace your A/C belt. To remove the belt you will need to loosen the tensioner on the belt using an 8mm Allen. With the tension off you can now replace the belt.

Installation is the reverse of removal

This photo illustrates the five different belts on the W126 (there are two belts on the water pump, power steering pump).
Figure 1

This photo illustrates the five different belts on the W126 (there are two belts on the water pump, power steering pump). The red arrow shows the air pump belt and the green arrow illustrates where the 6mm Allen bolt is located. Note: most of the front of the car has been removed for demonstration purposes.

This is what the air pump looks like from under the car.
Figure 2

This is what the air pump looks like from under the car. Loosen the 6mm Allen (green arrow) and then loosen the 13mm bolt (red arrow). With the bolt loosened you can turn the 19mm bolt (yellow arrow) and either un-tension or re-tension the belt.

Here you can see how the 19mm bolt has teeth in it (red arrow) and the toothed gate (green arrow) that the bolt turns in.
Figure 3

Here you can see how the 19mm bolt has teeth in it (red arrow) and the toothed gate (green arrow) that the bolt turns in.

With the air pump belt (green arrow) removed you can use an 8mm Allen to loosen the tensioner (red arrow) and then replace the A/C belt (yellow arrow).
Figure 4

With the air pump belt (green arrow) removed you can use an 8mm Allen to loosen the tensioner (red arrow) and then replace the A/C belt (yellow arrow).

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Comments and Suggestions:
91 Benz Comments: The place you show for the thermostat on the w126 420sel. The top of the engine is not where my thermostat is? I think what you show is for the SL model. I could be wrong I just know mine isn't there. Thank you for your services
December 8, 2016
Will Comments: What do you do if a 6mm allen wrench doesn't seem to fit
September 29, 2016
  Followup from the Pelican Staff: Try a 5 or 7. - Nick at Pelican Parts  
JB Comments: I have a 91 420sel Mercedes and it seems that this site has a lot of information that I could obtain I'm excited I'm also hands-on what work I can do myself I will I'm also in what can do myself I will
February 22, 2016
  Followup from the Pelican Staff: Glad we can help get you excited. - Nick at Pelican Parts  
lftdazd Comments: For the ac tensioner, you loosen the 19mm bolt, not the hex on the pulley
November 5, 2014
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. I will have the article updated.
- Nick at Pelican Parts
 
Fitz Comments: I loosed the tensioner and it just came off there was no tension on it, it was just a idler wheel. Do I loosen the bolt on the arm to adjust the tension ? I like the pictures and edits on your web site THANK YOU
Ray
October 9, 2014
  Followup from the Pelican Staff: What vehicle are you working on? - Nick at Pelican Parts  
jtaon001 Comments: What direction do you turn the AC belt's tensioner to loosen it? Clockwise or Counter Clockwise?
July 7, 2014
  Followup from the Pelican Staff: Loosen the 8mm Allen bolt counterclockwise, then the tensioner releases. - Nick at Pelican Parts  
ray Comments: This is great pictorial instruction from a beginners standpoint. It explains what's involved doing it the correct way.
August 21, 2013
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help. - Nick at Pelican Parts  

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