monch

Hi RX Owners, my wife's 2004 RX330 today refused to turn on the navigation screen and the AC. The whole top unit looks dead, no buttons work and no power on the screen. Well, as a result the rearview camera also doesn't work. I'd highly appreciate your advise on what/how to check and fix this!
The car starts and runs normally (Idle RPM is low though: 500RPM, I don't know if that depends on this issue yet). Radio works fine. The navigation unit in the trunk looks functioning, at least it makes disc-reading noises and is able to get the disc in and out. If it helps, the car has ML and rear seat entertainment (works fine). No check engine light either.

One thing me/my wife noticed recently, the screen power-up was sometimes taking unusually long time. Like you turn on the key, start the car, but the screen powers up 5-10 seconds later. I tend to think some electronic component was slowly getting bad and eventually gave up. Any ideas?

isfdude

iTrader: (11)

Check the fuses and if not you will have to replace the navi unit. Check eBay for a used one.

monch

Fuses checked, all are good. I've took out the unit and dismantled it to the bare circuits, measured and 12V power actually is supplied to the unit (M3 connector, pins 7,8). But the whole nav unit simply doesn't power up. Does anyone have any idea where we could find the super-secret schematic diagrams of this UFO? I'd be happy to check the power supply functionality, did not find any obvious cap leaks or blown parts. Power supply function should not be very complicated to check/fix, I wish I had the schematics handy ...

And as ill luck would have it, I'm on the last year of lexus gold warranty which DOES NOT cover this unit

monch

BTW, do you know what is the function of the coin battery welded in the unit? It was couple levels down the PCBs building so couldn't reach there to measure the health. Assume either maintain clock or memory (or both).

monch

Today put the nav unit of the friend, worked great. So my display unit is the problem. Moreover, we swapped quite a few modules between the working and non-working units, and pinpointed the main problem to be the main board on the back of the screen.
That main board is responsible for supplying the whole unit with different voltages, and apparently the supply doesn't work. I'll try to go over to see which component causes the issue. It's hard to me to spend $700-$1000 to get another unit, while the pcb tends to tell me a small capacitor/transistor/resistor may be the cause ... Anyone could you please help with schematic diagram, or do you know where can I get them?

05RX330TX

This is the only thing I disliked about the NAV/AC system on the older RX, this is a very poor designed by Lexus in opinion the AC unit control should be separate to prevent unnecessary expensive repair causes by other function.
Answer to your question I am not sure if the main board schematic diagram available to obtain but in my experienced with Electronics PCB normally there is P/N printed direct into the PCB, if there is one you can Google by the P/N.
Sorry, don't have much to help may be other members can share.