1988 L Rear Defrost

[purg3d]

I'm trying to add rear defrost to an 88 L. I have a wiring diagram for a 90 and it shows positive coming from the ignition switch (BK/W), 15A Rear Defrost (BK/W), and to the Rear Defroster Switch. From there, it supplies voltage to the Instrument Panel Indicator Light, Rear Defroster, and Electronic Control Assembly (BK/BL).

I was hoping to take power from the ignition and just run an in-line fuse to the Defroster Switch at BK/W, splice in the BK/BL wire into the dash light, and run it to the hatch.

Can I have rear defrost without my ECM knowing about it? Are the other 2 wires on the Defroster Switch just for interior lighting?

[kellen302]

All of the wiring should be there, except maybe in the hatch, if you get a hatch that has defrost you should be able to plug it right in.

[2xclutchin]

I dunno though, it might not be. I think I recall something that certain things weren't included in the harness if others were not on the car at time of Manufacture. For instance if your car had defrost it would have the harness for option A but if it didn't it would not.

I could be speaking out my rear on this, but I do believe I remember seeing this. Such as too how since I had rear defrost the wiring is there for rear wiper and tach, so I could install my tach cluster without running a tach wire.

Again, I could have made this up, but I also think the 88-89 are different than the others in some ways. So for what it's worth, I don't believe his would have that wiring. Can't help on the OP question though.

[purg3d]

Thanks for the replies. My 88 L was not wired for tach, defrost or rear wiper. I added a pin to the cluster harness for tach- hoping defrost will go as smoothly. I'll post a picture of the diagram:

[purg3d]

That's what I have done.

Everything works except the cluster light. I have the pin at 5:30 looking at the white connector; it's next to a yellow wire.

I may need another ground in the cluster.

Stay tuneed

[purg3d]

It was the hole at the 3 o'clock position. Light comes on, I get 12v on the defrost wire. Only thing left to do is run the wire. Given the weather, the upgrade is welcomed

[Flw Sock]

Can't you just put a wiper/defroster on and run it to the battery with a switch? That way it's always powered up when you need it! Why does the ECU have to know about a defroster, or a windshield wiper?