Blower Resistor Repair Guide 850/s,v70

[snookwhaler]

This is a guide for repairing the Blower Motor Resistor on a Volvo 850/S70 with manual A/C. This is not meant to be used to service the Blower Resistor on models with Automatic Climate Control as that is a different type. A new Blower Resistor for these cars can run upwards of $75 to $95 plus shipping depending on where you buy it. By following the Procedure below you can repair your existing Resistor for as little as $2 if you already have the Solder and Tools.

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.

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.

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.

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.

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.

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.

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.

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. I dissassembled my motor and found the bushings were dry but in good shape. So, I re-greased them with some synthetic grease and re-installed. It spins freely now and runs silent.

[AlvinL]

Very nice! I'll pin this.

BTW, what's the original thermal fuse rating?

[snookwhaler]

Thanks...

It is rated at 216 Celcius. They usually "pop" before the rated temp though. Using one rated up to about 230 would be fine.

One more thing... The reason I decided to do this is that I could not find a used resistor that was the older style with the small cannon plug. Most were the newer type like in the S/V70's. The only real difference is that on the S/V70 version, the Thermal Fuse is on the "end" of the Resistor Pack instead of "beneath" it.

The job was amazingly easy. And super cheap. Probably the single cheapest fix I have done on the car.

Here is a couple pictures of the different resistors. The one on the left is from an S/V70 and the one on the right is off an 850. I have been told that some of the newer resistor packs are in the later model 850's. But, I have yet to confirm this.

Top

Angle

Plug

[Ozark Lee]

The biggest problem I see with this is that a standard 60/40 (Tin/Lead) solder melts at 190° C. I would be inclined to use a low grade silver solder and heat sink the thermal fuse while soldering it in. I think from the factory they spot weld the leads due to solder limitations.

...Lee

[snookwhaler]

Correct...

I am not teaching anyone to solder. If you don't know these things... You probably shouldn't do it (as mentioned above). I used a silver grade solder. If you look at the temp. of the fuse, this should be a no brainer.

The solder melting point is about as high as the Thermal Fuse. It is unlikely that the solder will fail before the fuse. But, if it does... That is fine. Something is seriously wrong with your relays, fan motor, resistor or wiring.

The old fuse WAS soldered on there. The wire loops coming out of the resistor are a "coated copper wire".