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How to Replace SC-900, 901 w Aftermarket Double-Din and Retain Factory Amp/Wiring

This how to tutorial DIY courtesy MVS Contributor avboden » 

DIY Overview

Most guides for this are very old and have broken photo links at this point. I recently did this so here’s a new how-to!
Time required: At least 2 hours
Note: Does not retain center speaker

Why Would I Replace My SC-900 or SC-901?

You have a factory system that is 6 or more speakers, and have an external amp that handles the crossovers to feed the tweeters. Re-wiring all of this without keeping the amp is a royal pain! These directions allow you to replace the head-unit while maintaining the factory amplifier and speaker wiring. ZERO re-wiring to the speakers is needed.

Parts Needed

TOTAL PRICE: $50-$70 + head-unit

See the Original Volvo Forum Post on MVS

Tools Needed

  • Philips screwdriver
  • T20 torx bit/driver for removal of center speaker and glovebox
  • Small flat-head screwdriver
  • Dremel, cordless if no access to power.
  • Grinding stone or cutter head for dremel
  • Drill and bit-set or equivalent for dremel
  • Wire stripper/crimping tool
  • Dust-buster style vacuum is handy
  • Optional – soldering iron

Step 1: Gather your parts and tools

Parts, tools and new Pioneer double-din stereo

Step 2: Take your harness adapter and remove all but these three wires (note, this guide is assuming you run your headlights 24/7 like a good person and don’t need to hook up the headlight wire to the headunit)

remaining wires.JPG
Remaining wires

Step 3: Shorten the wires a bit and connect to the matching wires on your radio’s harness. Attach the blue wire from the amp adapter to the blue wire on you radio’s harness (this blue wire turns on the amp when the car turns on). Note: If you have a power antennae this will also be hooked up to the blue wire.


Step 4: Use a key or coin to pop these out of your factory radio, and pull the radio straight out with them

pull radio.JPG
Pull the OEM SC radio out

Step 5: Unplug everything from the back of the radio. All we will need is the larger antennae plug, the larger connector with the power, and the DIN cable to the amp.

radio out.JPG
OEM radio is out

Step 6: Before we make any permanent modifications, plug in your adapter harness and everything to the new head-unit and make sure it works. You will be attaching the large plug with the adapter you made before, the DIN adapter, and RCA of the DIN adapter to the head-unit. Ignore parking brake interlock cable for now. Make sure to test your front/rear fader to make sure sure your RCA cables are connected appropriately. Modify as needed so front is front and rear is rear. Don’t trust the adapter without testing this, some maybe wired in reverse from what they advertise (mine was).

Radio wiring exposed
Test new stereo before installation!

Step 7:  (Note, you can do this step before getting in the car) With the Pioneer double-din installation kit, attach the side brackets to your new head-unit with two screws on both sides using the tapered screws that came with your head-unit. You will not need to attach the large rear bracket.

Step 8: Remove everything again. Stuff the car-side wires in and stuff the hole with some paper towels or a rag. Note the plastic rail on each side of the opening. This is the plastic we will be removing in Step 9.

to grind.JPG
Grinding the stereo seat – you’re removing the plastic rails

Step 9: Using your dremel with either a grinding stone or a cutting head, carefully remove the plastic rail from both sides. Stop frequently to let it all cool. Warning, melted/cut plastic gets HOT. Don’t catch anything on fire! I am not responsible if you burn your car down. Vacuum as needed.

done grind.JPG
Done grinding

Step 10: Press the double-din basket that came with the pioneer kit into place. It should go in easily and sit flush along the edges once in all the way.

place basket.JPG
Install new radio’s basket/housing frame

Step 11: If your press tabs on the basket don’t line up with the existing holes in the plastic, score with your flathead screwdriver edge around the outer two press-tabs on the basket on the bottom and both sides. You should have 6 scored in total

Step 12: Using your drill or capable dremel attachment, carefully drill/cut out the areas you had scored. This doesn’t have to be super clean so don’t worry if it’s ugly. Photo is after I drilled out what I needed. Careful not to drill into what’s below the area.

cut holes.JPG
Cut holes

See the Original Volvo Forum Post on MVS

Step 13: Press the basket back into place, and using your flathead screwdriver, press the tabs down into the holes you made until the basket is tight

bend pins.JPG
Bend pins

Note: Steps 14-18 assume your head-unit uses an external microphone for bluetooth phone calling

Step 14: Using your T20 driver, undo the screws holding in the glove-box. Yank the glove box straight out.
Step 15: Using your flat head screw driver, pry up the edge of the cover over the center speaker on the dash. It takes a little force but it pops off eventually.
Step 16: Also using the T20, remove the center speaker
Step 17: Feed your head-unit’s microphone to the right, stick your hand in through the glove-box hole for guidance. Once through there it can be easily routed behind the radio by looking through the glove-box hole.

center mic.JPG
Center mic

Step 18: Replace the center speaker, cover, and glove-box. (optional: Remove the center speaker from the bracket and only re-install the bracket). The microphone wire will fit underneath the speaker’s bracket on the front left corner (front being towards the rear of the car)

done mic.JPG
Center mic installed

Step 19: Run the parking brake interlock-wire (long green wire from the new head-unit) down and into the trans tunnel trim. I was able to do this without removing anything but the trim on the parking brake itself(which you pry to the left and then off). Connect this wire to the single wire on your parking brake sensor. *optional* skip this and install the bypass

Step 20: Plug in all your various adapters to your new head-unit, tuck the unused wires back, and set the new head unit into place. This is the time to plug in any AUX input cable or USB cable you may also want to run from the new head unit and route them wherever you want. It should push back flush with the newly installed basket. If it won’t go in all the way, take it out and work on tucking the wires back better until it slides in easily.

place radio.JPG
New stereo is in final configuration and seated

Step 21:Screw in the 4 phillips screws that came with the pioneer double-din adapter kit to hold the new head-unit in place to the basket.

screwed radio.JPG
Screw in the new radio to its housing seat

Step 22: Press the trim that came with the pioneer double-din adapter kit into place. There is a small gap on top if you’re picky you can custom a better trim piece.

done radio.JPG
All done! Finished! New stereo in your Volvo! Whoo!

YOU’RE DONE! ENJOY YOUR NEW HEAD-UNIT RUNNING THROUGH THE FACTORY AMP! Don’t forget to set the clock and program it as you see fit. Make sure your pre-amp RCA outputs are set to “full” or “rear” and not to “Subwoofer”

See the Original Volvo Forum Post on MVS

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