defroster from remote start Lexus rx300

I've just gotten the Viper 591xv remote start installed in my 2000 Lexus RX300, but ... they couldn't get the front defroster and rear window/mirror heaters to work.  The intent was to hook these two up through relays connected to the auxilary channel so that they are user selected once the car is running. They claimed to have spent two hours trying. 

Does anyone out there know the best way to do this for a 2000 Lexus RX300? 

The issue seems to  be that the switches may be integrated into the center consolue and may require hooking up by connection to traces or components on the circuit board.  ( I haven't looked because I'm afraid of breaking plastic as we're in a bit of cold snap right now... However, I'm not afraid of the approach if that's what I have to do to get this to work.) 

Thanks for any help/advice.

Steve MacLeod

Actually, jumpering the switches with relays and connecting  the relays to the "defroster output" on the 591xv was my first thought, but the installer advised that the customers who have that done often ask to have it "undone" when the next summer comes around.  They now advise all customers to put defrost functions on a second channel.  For them it means connection to Aux rather than Defroster, so it's no extra work for them.  I really have no other perceived "need" for the aux channel, so it seems ok with me.

Do you see it differently? 

I obviously didn't do a good job explaining the issue....

On the RX300, the buttons for defroster and defogger are on a center console and they depress momentary contact switches that are surface soldered onto a circuit board, which is buried in the middle of the combo stereo/heater control/security system.  The timing circuits and all are on the circuit board.  It doesn't matter how you want to control it, there is no (simple) wiring to get to... 

So, I've just finished removing everything and soldering a small wire onto each side of the little itty bitty switches.  I've reassembled it and it all works as intended.  I've left the wires "out" for now and I'll take it back to the shop to be connected to relays and controlled by the remote.

I've thought about pros/cons of automatically getting the defroster going and using a summer/winter toggle vs. hooking it up throught auxilliary control.  I think I'll go with the latter.

Thank you all for your help.

Steve

Steve,

That's exactly how my rear defrost button is, i've been trying like crazy to get my aux 1 to turn it on, but it wouldn't.  The diagram for my car, shows me a wire for the defrost switch, but when i used it, nothing, or at least i don't know, because the led on the button is coming from a different wire. I've taken out my heater control panel, to examine and the  rear defogger button is just as you described, connected to a circuit board, i'm  lost on what wire to connect to (using relays) to get the rear defogger to turn on by remote.

My installers gave me a very similar story - they tried to hook using the wirnig, but nothing seemed to work. I suspect that there is a logic check in the head unit that won't let you control the relays when the head unit is set to something else (ie., you may not be able to control defrost and defog when the head unit is calling for heat to your feet and face.)

I probably should have taken photos - cuz I'm not going back in there!!

I pulled the whole head unit completely out and apart - very scary...  On the circuit board - behind the buttons for defrost and defog are little tiny momentary contact push buttons that are surface soldered to the face of the board on all four corners of the switch.   It turns out that the two lower corner solder joints are in common between all the switches in that row and either of the upper two solder joints of each switch are the other side of the circuits.  I soldered little tiny wires to the common side of one switch and followed the traces for the other side of each switch - I found a plated through-hole between surface resistors R28 and R29 for one circuit (defrost?) and between R20and R30 for the other (defog?) and soldered a wire in each hole.   Yes this was scary - and I probably should have taken pictures.  You won't want one of those 1200 watt Weller's for this job!!  I ran the wire out on the bottom of the plastic frame - and hot glued it there and then ran it over under the drivers side panel.

Now, when you "jumper" each switch, it works.  The inputs don't seem to be debounced, so sometimes just touching the wires together to causes them to turn on/off - I suspect that the relays will solve that  - and will let you know later.

Would you be willing to share your wiring info?

Hope this helps.

Steve

It isn't rocket science to understand, but doing it isn't for the faint of heart.  Some experience working with surface soldered component boards would be a good idea. 

Given the potential for damage to that center display unit, I can understand why an installation shop probably wouldn't delve into this without a complete waiver of liability. (Hmm, I wonder what that center console goes for...)

Still, if you are handy and you want to give it a go, it's eminently doable. 

I've got an appointment tomorrow with the shop to finish up the install they contracted.  If all goes well, by noon I'll have the only Rx300 in this quadrant with remote defrost and defog.