Question about Mercedes-Benz 420-Series

3 Answers

While driving, the A/c blows nice and cold. When in slow traffic or at idle (stopped at a light) it does not work as well. The freon is full. Any suggestions?

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  • bnivek Jul 26, 2009

    Thanks for the info. I will check it out but how will I know if both speeds are working?

  • bnivek Jul 26, 2009


    i started the car with the a/c off. Turned it on and after about a minute or so, the fan kicked on but it seems to only have 1 speed, high.

  • bnivek Jul 26, 2009

    Hi greenspan, are you referring to a vacuum leak for the a/c problem I am having?

  • bnivek Jul 26, 2009

    I checked for debris and there is no blockage, just some old dust but I can see through the cooling fins. I can't tell if it has 3 wires or 2, as the wires are in a tube. I would have to remove the fan to even see if I can see how many wires there are. Can I safely clean the condenser with a pressure sprayer just to remove the normal dust that might have collected over the years?


  • bnivek Jul 27, 2009

    I'm sorry, you are right. It is a 1988 429SEL.
    Thanks


  • bnivek Jul 27, 2009

    Good idea, I will get a kit and do it. Thanks.

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This is a symptom of a low refrigerant charge, u have a leak, the most common cause of leaks on your car is the AC compressor shaft seal, adding a can of stop leak may cure this for awhile, to do this add about 8 oz's of the recommended refrigerant (u don't say year) to your system at the low side charging port, that is in the larger of the two lines coming from the AC compressor. Buy a recharge kit, it comes with instructions on how to install the refrigerant and know when the system is full, Kragen and other stores like Autozone carry these kits, they are about $25.00

Posted on Jul 26, 2009

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You possibly have a vacuum leak... Vacuum leak is usually under the battery or right at the intake manifold. I've had leaks at both places.

Posted on Jul 26, 2009

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Yes i have a suggestion. Is the ac condenser fan working in front of the radiator working on high speed when the air is on? If the fan does not cool the condenser down enough the air will be warmer that is why when you drive down the road the outside air naturally cools down the condenser but at idle or slower speeds the ac relies on the ac condenser fan to keep it cool.The fan should be a 2 speed fan the high may not be working ,if not the fan needs to be replaced .:)

Posted on Jul 26, 2009

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  • mike loshbough
    mike loshbough Jul 26, 2009

    Does the fan have three wires going to it, If so then the fan has 2 speeds.Also the fan could be working but not putting out enough force.Also look to make sure there are no leave or other debris in front of the condenser to restrict air flow .

  • mike loshbough
    mike loshbough Jul 26, 2009

    Yes you can if you can find a air hose with a blower fitting on the end and then blow inwards that should remove any debris :)

  • mike loshbough
    mike loshbough Jul 26, 2009

    Was your ac charged recently? If so it could have to much freon which would cause the freon flow to be slower at idle.

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