Results 1 to 3 of 3

Thread: Adapting BMW PW Switches and Relays to an '88 Avanti How-to long and pictures

  1. #1
    Senior Member
    Join Date
    Sep 2005
    Dobson, NC, USA.

    Adapting BMW PW Switches and Relays to an '88 Avanti How-to long and pictures

    The window switches on the '88 "beater" Avanti have been giving me fits since I've gotten the car. In fact the power windows have been the only real problem I've had. It needed a motor on the driver's side and a gear on the passenger side. It has since eaten two more gears over there so I need to find out why but that's another post.

    Most later cars use reverse polarity motors for the windows. If you have only two wires to your motor it's a reverse polarity motor. The way it works is that one wire is powered while the other is grounded to spin the motor in one direction and vice-versa. Most cars have relays in the circuits but not my '88 Avanti. It has switches that were altered, I assume by Avanti Motors, to take care of all the powering and grounding.

    I took the switches apart a couple of times, cleaned, lubed adjusted etc but just when I would really need the windows to go up or down they would fail. So I went on ebay looking for some switches that would fit the console and found dozens of BMW window switches for sale. I bought 4 for $9.95 plus shipping. I figured for the price if I couldn't make them work it was no great loss. The nice thing about the BMW switches is that they are like two separate switches in one and the push down to activate design doesn't require any type of rocker or pivot to wear out.

    So much for the history. I took one switch apart and saw which connector would transfer power to the up side and the down side when each was pushed. No matter how many connections the switch has you only need the main power connector and one connector that gets power when you push up and one when you push down.

    I went on Amazon.com and found 5 pin Bosch style relays with wiring harnesses from a company called Uneeksupply. Great deal at 10 relays for $24.10 including shipping! You'll need 4 relays for the job.

    So heres how you wire it up without even having to cut a factory wire or run a new power lead or ground.

    Remove the shift handle by prying out the 'u' clip at the front of the handle. You need to shift the car out of park to get to it easily. Next pry the console plate up at each corner. It's held on by spring clips and should pop out easily. Remove the connectors from the switches. I took the wires out of the connector but it's not necessary. If you want to pull them out you need to put a stiff wire or wire pick behind the spade connector to relaease the one way lock and pull the wire from the connector.

    the wire coding is as follows for the switches:

    green (both sides)=ignition power 12V

    black (both sides)=ground

    yellow and black= driver's side down

    orange and black=driver's side up

    yellow = passenger side down

    orange = driver's side up

    I don't know if all relay harnesses are color coded the same way so if you are doing the job the number on the relay takes precedance over the colors that being said here's the connections to the relay with numbers and colors:

    Each side will need two relays, one for up one for down.

    Twist terminal 86 and 87A wires from both relay harnesses together and crimp on a yellow solderless male spade connector. Attach that to the black ground wire from the factory harness.

    Terminal number 87 needs to have a wire added. So twist an additional 7 " piece of 14 ga wire and crimp on a yellow male spade connector to the two 87 wires from the relays. The connector needed on the additional wire is determined by the switch you are using. If its' a BMW switch then you need a narrow blue female spade connector. Connect to the green 12V ignition wire.

    Cut two 7" wires and attach the narrow blue female connectors to one end and wider blue male spade connectors to the other. These wires connect to the switch and one will go to the up relay and one to the down. Connect one to the 85 terminal on each relay.

    Finally, put a wider male spade connector on the 30 terminal wire from each relay and connect that wire to the orange or orange and black for the up relay and yellow or yellow and black for the down relay.

    To simplify if you buy the relay and harness and the colors match up to the harnesses I have here's the color connections:

    White and black (86 and 87A) from each relay to black from factory harness.

    Yellow (87) from each relay to green from factory harness. An additional wire needs to be attached and connected to the power terminal on the switch.

    Red from each relay harness (85) to either the up or down output terminal on the switch.

    Blue (30) from each relay to either orange/orange and black for up or yellow/yellow and black for down.

    Remember one relay for up and one for down but you can share the 12V ign and ground for both and you only need one wire from the 12V ign to power the switch.

    Last edited by bige; 06-25-2010 at 09:28 PM.

    1988 \"Beater\" Avanti---R2 R5388 @ Macungie 2006

  2. #2
    Senior Member N8N's Avatar
    Join Date
    Oct 2004
    Falls Church, VA
    I guess now would be a bad time to tell you that the power window switches in my '88 535i were a neverending source of frustration... I just couldn't keep the damn things from oxidizing.

    Fortunately once you've popped one apart and cleaned the contacts it's a 10 minute job next time around...

    The nice thing about those switches is some of them are orange-red backlit which would look good in an Avanti interior. Might want to see if yours are like that. Don't have a pinout, sorry. The stock ones on an '88 were not backlit, but the ones that the BMW dealer sold as replacements about 1999ish were. (there was one that I couldn't bring back to life and had to replace; I put it on the sunroof so it wouldn't stick out like a sore thumb.)

    55 Commander Starlight

  3. #3
    Senior Member
    Join Date
    Sep 2005
    Dobson, NC, USA.
    Mine are backlit...If the BMW switches can be cleaned and kept working it's OK with me. The Avanti switches are crude and the lack of relays bothered me. I'm thinking of buying more and replacing the rest of the junky switches.

    I also bought a couple of Porsche rocker style switches but they are packed somewhere in the 40 or so boxes I haven't unpacked yet. With the relays almost anything that fits in the hole can be made to work.

    1988 \"Beater\" Avanti---R2 R5388 @ Macungie 2006


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts