RX300 Windows Tech Brief

There are probably many suitable relays available from several manufacturers.  I picked a Panasonic Relay because the RX300 was originally fitted with Panasonic parts.  The ACJ2112, available at Mouser Electronics, seemed like the best pick, but there are others that will work in this situation.  What you need first is the datasheets for the specific relays that are being cross referenced.  The CR2-12V is the original relay, and the ACJ2112 is the replacement.  These are excerpts from the datasheets.  This is the original CR2-12V Relay...

You are specifically interested in the PC Board pattern, and schematic of the Relay.  This gives you the information about how the relay is wired onto the Door Control Board.  Now here is the ACJ2112 part specification.

Note that the ACJ2112 is considerably smaller than the CR2-12V.  Both parts are shown from a bottom view, but we will be using the Dead Bug Technique to wire in the replacement relay, so the connections will be mirrored vertically relative to the CR2-12V part specification drawings, example below.  Here is a shot of the Dead Bugged Relay.

Alright, this is where it gets tricky.  You are looking at the top side of the circuit board, so the CR2-12V footprint is mirrored vertically.  Then we are going to put the ACJ2112 down, up side down, within the CR2-12V's footprint, with the common contacts oriented to the right, to the window motor.  The Normally Open, and Normally Closed contacts go to the power supply side.  Then the coil contacts are in the middle.

I cropped the schematic diagrams out of the part specifications, and reoriented them to the positions they have in the photo above.  Notice the way the common contacts are touching the Normally Closed side of the relay, and how they are both on the top.  Here we have aligned the relay switching position.  This is how you verify that the up switch will make the window go up, and not down.  There are three opportunities here to wire this backwards.  The common connections go to the window motor, wire them backwards, and the window works in reverse.  Like wise if you wire Normally Open, and Normally closed backwards the window also works in reverse.  If you get the control signals to the coils wired backwards the window works backwards.  So you really need to pay attention to which wire goes where.

As for wiring, the heavy current wires are Commons, to window motor, and Normally Open, and Normally Closed, which go to the power supply.  These wires can carry 20 Amps, so they need to be at least 18AWG, 16AWG would be better if it will fit.  I plan on using 18AWG Solid wire to connect the heavy current terminals.  Soldering large wire like this will require a soldering iron with enough power to heat the larger mass of the wire, and circuit board.  If you are having trouble getting the solder to flow, find a more powerful iron.  The solder joints carry current, and need to be flowed correctly.  The coil wire, as you can see in the specification above, only carry about 50 milliAmps, so the control wires to the coils can be 24AWG Solid wire.  I used a 5 minute epoxy to glue to ACJ2112 to the circuit board.

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 Ultimately I wound up replacing these with aftermarket boards.  There are a lot of cheap Knock Offs now.  The first sucked, literally, and would drain the battery.

The second worked better, but has a glitchy thing with the locks when I close the driver door.  Cheap Knock Off are just that.  It would be nice to get some genuine Toyota parts, LOL!