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850 S70 Blower Resistor Repair

Published on December 31, 2011 by SnookWhaler

Always check fuses, cannon plugs and other connections before taking your car apart for major repairs. Remove the key from the ignition and switch the interior lights off. Open the glove box door and remove the 6, T25 torx screws that hold the glove box in.

 

Remove glovebox door

 

With a thin bladed screw driver, release the glove box door straps. Carefully pull out the glove box taking care to work it around the latch at the top. Remove the 4, T20 torx screws securing the glove box door to the dash. Remove the glove box door. Note: You do not have to remove the door. I just like to remove it, to reduce the risk of breaking it.

 

Remove the 850 torx

 

At this point you can choose to remove the knee bolster. You do not have to remove it. But, I find it saves a lot of swearing if you remove it. There are only 3, 13mm nuts that hold it to studs. You will need to remove the lower dash access panel to remove the knee bolster. Remove the lower dash panel by removing the 3, T25 torx screws beneath the glove box. There is one on each side and one in the middle.

 

S70 resistor

 

I use a small spring clamp here to turn off the glove box light. Or you can unplug it. You can access the blower resistor through the glove box opening or from below. I find it easier from above. With a T15 torx bit remove the one screw securing the resistor. On some cars it may also be necessary to remove a "wire loom support". The support bracket surrounds the resistor and is also held in with 2 T15 torx screws. It may be necessary to access these from underneath which will require removing 3 more T20 torx screws for the lower dash access panel.

 

Wires for 850 blower motor

 

Once these pieces are removed, remove the Blower Resistor at an angle pulling on the tab with the screw hole "outwards" and pulling "up and out". Once it is out of the hole, pull it down to unplug the resistor. CAUTION!! USE EXTREME CAUTION WHILE HANDLING THE RESISTOR, AS IT CAN REACH TEMPERATURES UPWARDS OF 200 DEGREES CELCIUS. Unplug the resistor. Check the thermal fuse with an ohm meter to insure it is blown before proceeding. Remove the old thermal fuse with a small pair of side cutting pliers.

 

Volvo repairs 1995

 

A new thermal fuse can be found at just about any electronics store. I got mine at a local store for $1.00. Places like Radio Shack has them for $3.00. Use a thermal fuse rated for between 216 and 230 Celcius.

 

compare resistors 1994 volvo

 

Clean and prep. the surfaces before installing the new thermal fuse. "DISCLAIMER": I do not have the space here or time here to teach you how to solder. So, if you are not familiar with soldering small electronics, do so at your own risk. I am not liable for anything you do to your car or what happens as a result of repairing your own blower resistor. I recommend using a "heatsink clamp" on the thermal fuse to keep from damaging the fuse while soldering. I also recommend using a 10 watt soldering iron designed for soldering circuit boards. Using a larger soldering iron may damage the new fuse and existing resistor. Install the new thermal fuse onto the blower resistor pack.

 

resolder resistor

 

Check the resistance across the fuse with an ohm meter after the operation to insure success. Install the resistor by reversing the above removal procedures.

A blown "Blower Motor Resistor" is usually indicative of a failure elsewhere in the A/C's electrical system. A blown resistor will not allow you to use the first 3 speeds on the fan motor. Too much current draw at low fan speeds are what blows the resistor. Usually due to a "Blower Motor" that is failing internally. Or bushings in the motor that have become dry. All these issues are commone in 1993, 1994, 1995, 1996, and 1997 Volvo 850s and S70s

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