Question about 1996 Volvo 850

2 Answers

Change fan switch as it only operates on high setting

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  • bobeyond Nov 15, 2010

    last material was relevant to replacing heater core and fan. I only want to change a rheostat or resistorso that the fan will operate on low settings

  • bobeyond Nov 15, 2010

    Thank you for this information. I will try to find a new relay after I am able to get to the old one. What is the best advice to get to that relay.

  • bobeyond Nov 15, 2010

    There are two resistor type plug in boxes on the left side behind the glove box one is a Hella (blue) Volvo 99130270 5 post and the other is

    Volvo (black) 91 28 134 ?
    / 898705 000 or 090993 4 post> Are these what I am looking for??

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  • Master
  • 2,299 Answers

Fan resister located near the blower motor underneath the glove box. L,M,MH operate on resistors and high speed bypasses the resistor so your resistor plug is burnt out on the first three speeds if you still have high speed.

Posted on Nov 15, 2010

  • Rodney Clark
    Rodney Clark Nov 15, 2010

    It is under the dash on the passenger side behind the glove box.

  • Rodney Clark
    Rodney Clark Nov 16, 2010

    Yes. I believe that you are right. One of them controls the speeds 1-3 and the other is for speed 4. Also you can check fuse number 31. This is for this resistor pack. I can't remember off of the top of my head which pack is the one for the fans 1-3. But you can unplug each one and see if the fan stops with it on hi.

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  • Volvo Master
  • 17,970 Answers

Your blower motor resistor is probably shot. If the blower is making noise than the only thing you can do is replace it.

There is a variable resistor with a heat spreader on top which varies the amount of current that the fan receives. The resistor is known to go bad after 10-15 years, depending on use. He got a replacement resistor for $10, swapped them, added some thermal paste on the heat spreader.

Blower resistors typically operate by dropping voltage through a set of resistors. The lower the speed the more resistance is needed. High speed requires no resistance and usually bypasses the resistor assembly.


Also, I suggtes check this information about 850/AC-HeaterSystem-Manual (pdf)

Keep us updated.

Posted on Nov 15, 2010

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