1992 Ls400 Power Windows And Sunroof Don't Work

[kajman]

At some point in the past couple months, all the power windows stopped working on my 92 ls400. Fuses and circuit breaker appear to be ok. I have the wiring diagram and have tested power at the circuit breaker (ok) and power at pin 9 in the connector for the master control switch. With the key on, pin 9 has no power. I suspect the power main relay or the theft deterrent ECU that activates it but I'm having trouble locating the relay (not sure where to look).

Is there one relay that controls both the power windows and moonroof and if so, where is it? Or is there something else I should be looking at? Any help would be appreciated.

- Kaj Moenck

[fsuguy]

Kajman,

Have you checked that your battery is putting out enough voltage? On my '92, when the battery was on its way out, quirky things began happening, and all cleared up with a new battery! The onset of the cold weather and concurrent electrical problems appear to be related in the case of your '92. Will try to locate the diagram and post a pic later tonight or tomorrow.

[MrLatifa]

window.moon wiring.pdfwindow wiring.pdflocator.moon.pdfcomponent locations.pdf Looks like the problems you are having are NOT directly related to the same relay or fuse protection devices. If a pic is worth 1000 words, heres a long conversation.... let me know if this help any.

[kajman]

window.moon wiring.pdfwindow wiring.pdflocator.moon.pdfcomponent locations.pdf Looks like the problems you are having are NOT directly related to the same relay or fuse protection devices. If a pic is worth 1000 words, heres a long conversation.... let me know if this help any.

Didn't think of the battery as the car was starting fine. But it does make me wonder. After starting fine, we had left the car sitting for about 5 weeks a couple months ago and the battery was dead (or close to it). Seemed to be having a problem taking a charge on the charger high setting w/o getting an error so I charged it on a lower amp and it fully charged and then it started ok even after sitting for a 10 days. But when I check the voltage at the circuit breaker and fuses I sometimes got 10.5 and sometimes got 11 volts. Wonder if the problem is really a bad cell on the battery? Didn't really suspect it as it was only about 2 years old. I'll put the volt meter directly on the battery and see what I;m getting and then go get a new battery

[curiousB]

If the battery can start the engine and it is not running dead on you with normal day to day driving (ie the alternator is topping it up fine) then it probably isn't the battery. The starter motor draws 30X the current the window motors do, maybe even more. If it were battery or alternator you would see strange things with other electrical items as well (dim headlights, slow wiper blades, dead battery unable to start car, and slower A/C blower motor).

Since it is multiple windows and your less than positive declaration of the fuses "appear to be ok" then I would double check that. Maybe switch a fuse of the same value for another circuit and see if the problem moves around.

If not the fuse it could be a broken wire in the door hinge. These do break over time from all the flexing back and forth each time door opens. Drivers door most likely suspect. You might have to pull the drivers interior door panel off to take some measurements at the window motor and switch to narrow this down.

[jaswood]

The lock-out PB stuck in the lock-out position...?

[kajman]

Lockout PB has been tried both ways. I checked the battery - 11.8 just sitting there and 13.5 with the car running so i think the battery is fine.

Which fuses and relays would be involved that would affect both the power windows and moonroof? I know there are separate relays but do they both use the same 30am circuit breaker in the passenger fuse box? I checked that and it was good and also had power going through it. From what I understand on the wiring, with the key on the theft deterrent ECU powers the relay for the power windows and allows the circuit breaker to send power down to the master control switch on the drivers door. I have power at the circuit breaker but no power at the door leading me to believe the ECU has something to do with it (checked it's fuse and that is good too). I'd like to check the main relay for the power windows to see if that is working but I'm having a difficult time finding it. It is sposed to be on the fuse panel in the passenger compartment but there is nothing obvious plugged in that I see other than fuses and circuit breakers. Anyone have a diagram of where this main relay is located on the fuse panel? or back to my original question - what fuses and relays would be involved in affecting both power windows and moon roof?

-kai

[fsuguy]

Kajman,

In the '92 LS400, the power window relay is beneath the driver side dash on the reverse side where the fuses are laid out (junction block #1A&B). You have to unscrew a couple of bolts/screws to drop the junction block, on the reverse side are about 5 relays. "B" is the window relay.

I would suggest you try a known good battery before you go through all the trouble of dropping all the panels, etc., to potentially save yourself some time.

I am attaching a sketch of the junction block (1992 LS400)with the placement of the relays - it's only a sketch since I have no way of copying the diagram. The layout is:`

A. Tail light control relay

B. Power Window

C. Defogger relay

D. Fog Light Relay

E. Turn Signal Relay

F. Integration Relay

[kajman]

i know the bolt you are talking about - i was half way there but didn't think of anything underneath the junction box and didn't remove all the way.

did you attach something? i don't see it. you still suspect the battery even though it has 11.8 at rest and 13.5 when the car is running? i can try the battery route - just don't have one laying around at the moment.

[soda]

I have a 1990 ls400 and the moon roof is touchy sometimes and the rear passenger window won't roll up (goes down though). A few months ago I lost brakelights, turn signals and hazards on my Ford Expedition. A little wd40 in the hazard switch cleaned the connection and fixed everything. I'm gonna try this on the LS driver switches tomorrow. Sorry if I hijacked your post or thread just had a thought.

[fsuguy]

Kajman,

Sorry about the post missing that attachment - I sketched a picture of the underside of the junction block #1, giving the layout of the relays, from the repair manual. However, I don't see any way to attach it to this post. There does not appear to be a simple way for me to attach the pic through this system(?)

If you drop the fuse plate, however, there are 6 relays, one of which is the "B" relay for your windows. There should be two screws holding the plate in position. The relay of interest is one of the nearest two relays near these two screws.

[billydpowell]

Idle thought.... do the 92's have the option of holding the key in the unlock position to lower the windows and open the sun roof?

[kajman]

Kajman,

Sorry about the post missing that attachment - I sketched a picture of the underside of the junction block #1, giving the layout of the relays, from the repair manual. However, I don't see any way to attach it to this post. There does not appear to be a simple way for me to attach the pic through this system(?)

If you drop the fuse plate, however, there are 6 relays, one of which is the "B" relay for your windows. There should be two screws holding the plate in position. The relay of interest is one of the nearest two relays near these two screws.

Well - those screws to get the fuse plate out are more of a pain to get to than i thought. And I'm thinking the relay is not my problem since my problem involves both the sunroof and power windows and they are on 2 separate relays. The only common thing is the 30 amp Power Window CB (which operates all power windows including sunroof according to lexus manual) which I checked and it is not tripped and also has 12.6 volts running across it but neither the power window master or the sunroof has any power. But based on the attached wiring diagram, the CB sends it's power through the relay which is operated by the Theft Deterrent ECU.

1) Is it possible the theft deterrent is not opening the relay? If I could locate it I'd check for power off the pin going to the relay. I haven't noticed anything else not working.

2) This schematic doesn't show pins 1 and 2 on the master control switch but the moonroof one you sent me had them going back to the same theft ecu. Tied in to the door lock switch I think. Is that possibly part of the problem?

3) It seems odd that there is no power and it used to work until the battery drained. Would a drained battery affect the Theft ECU?

Unless the power window relay also sends power to the sunroof relay, this just seems to be a problem related to the ECU otherwise I spose the power relay could be the problem (hoping not to have to pull the fuse panel). Besides the under-dash panel, what exactly do I have to drop to get to the screws that allow me to drop the fuse panel?

2008-11-08_191416_ls_window_schematic.pdf

[kajman]

Just to close the loop on this - I finally tracked it down. After the relays tested good I was hunting for the Theft Control ECU and noticed there was a unit behind the fuse panel on the firewall with one connecter half way out. I pushed the connecter back in and walla....the windows all worked. It was the Theft Control and the connector was the one that supplied power to the relays to operate the circuits. And so far since I did that, my traction control light stays off (used to stay on all the time). Not sure if related but happy none-the-less. And I learned quite a bit about the electrical of the car along the way.

-Kai

[fsuguy]

kajman,

good for you! Thank you for posting your solution!!

[Steven Lemus]

On November 10, 2011 at 8:02 PM, kajman said:

Just to close the loop on this - I finally tracked it down. After the relays tested good I was hunting for the Theft Control ECU and noticed there was a unit behind the fuse panel on the firewall with one connecter half way out. I pushed the connecter back in and walla....the windows all worked. It was the Theft Control and the connector was the one that supplied power to the relays to operate the circuits. And so far since I did that, my traction control light stays off (used to stay on all the time). Not sure if related but happy none-the-less. And I learned quite a bit about the electrical of the car along the way.

-Kai

Im having the same problem were exactly is the fuse panel were you found the problem