Hi all. Just picked up a 1994 LS a few days ago and wan't to address that the heat won't work. I turned on the heat full blast and smelled it to see if it smelled like coolant, which it doesn't. It just blows outside air. I also checked under the car for leaks but didn't find any. Also checked the fuse on the drivers side, not that either. Not sure if it is indeed a bad heater core, or if something else. I found a video on youtube on how to flush your heater care and might consider giving that a try? I've done some digging online and on the forums here and haven't found any good DIY on how to replace 1st gen LS heater core. I found this post (https://www.clublexus.com/forums/ls-...ater-core.html) where someone did it, but it's not really a DIY. Not really sure if the heater core itself is officially the problem however. Is there some electronic actuator for the heat that could be malfunctioning? Any and all input is much appreciated!
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There is a valve that a solenoid of some sort uses to turn on and off the water. Its just above the passenger side of a normal US car valve cover with the hoses and cable attached to it. Heater core and evaporator big job. And the heater cores are super expensive.

 

Like dicer said, check the heater vavle first. put it on max hot and then max cool to see if it moves. You can check for any codes, (if your screen isn't blacked out) to see if the servo motors are not moving the doors on the heater assembly to adjust the temp. http://www.lexls.com/tutorials/air/accodes.html
There was no DIY for the core when I did mine but I had the manual and I listed the page numbers for everything ya need to take out if you can get one or find it online.

 

Im assuming this is the valve you speak of. I turned it to max hot and max cold and it did not move. It also looks pretty filthy, so this could be the culprit.

 

Yes that is the valve. It looks in pretty bad shape like it could be seized or something. You can try pulling the cable off and try moving it by hand. It should move easy both ways. I heard of someone who's cable was bent and it didn't pull the valve so see if your cable moves after unhooked.

 

Good news!! I pulled the cable off and manually positioned the control valve all the way down and it blows hot air! The cable doesn't want to come out very far, but fiddling with the control valve it seemed to move ok. It actually seems to be leaking coolant where the lever screws into the assembly, so there may be an o ring that needs replacing, or possibly just the whole thing needs to go, but thank God I don't have to replace my heater core!

 

Also, when i put the cable back on and tested the hot air again, it worked, yet the cable hadn't moved. Could've just been because it was already warmed up from being activated? The arm on the control valve seems to move ok, so maybe it is indeed the cable?

 

If you end up replacing that valve and want a Lexus part, here is an example.
http://www.lexussouthatlantaparts.co...rimLevel=19107

 

At least ya figured that out but now ya know you have a problem with the cable itself. It might be a servo motor which adjusts the cable not working. That's gonna take some digging to figure out. The servo motors are located in the heater assembly, not the blower assembly.

 

Update: I'm almost positive that it is the cable that's causing the problem. It wont pull out far enough. In addition to that, the control valve is leaking like I already mentioned and corroding everything beneath it, so that'll have to be replaced. Replacing the valve should be straight forward.

Edit: Found that the valve is actually pretty hard to move. Also, the cable does not want to move much either. I think the leaking coolant is the cause for the cable not wanting to move since its covered in coolant. I'll clean up the cable and see if it moves any better.

 

I found this thread that talks about the heater core as well, and someone on there said they replaced their cable with a piece of coat hanger. Post #3: (https://www.clublexus.com/forums/ls-...need-help.html) They said the motor is under the dash, on the drivers side. I looked and found one, but couldn't see much of it since its hard to get my head under there. I'll definitely continue the investigation.

 

Another Update: I took a look at the cable while it was moving, and i noticed that just the inner part of the cable moved. By that, I mean just the metal cable inside the black cable cover, was moving. And my cable was bent at 90 degrees, so i fixed it and tried turning on AC again and it bent it again. I also cleaned all the coolant off the cable, but it still won't move in the engine bay. I currently have the cable disconnected in the engine bay. It might have bent initially because it couldn't turn the stiff control valve. Here's some pics of the leakage.

 

Good to see you're finding the problems and the fixes by searching. I didn't remember those threads you linked to b/c it's been a while since I did some of that work. That's why "search" is your friend.
That's a lot of leakage on that lower dash panel.You might have a bad heater core. Try to follow the stains to see where they lead to.

 

Upon further investigation, I found that whenever the control valve is open, it leaks a lot of coolant where the lever arm attaches by the screw to the control valve itself. At this point, I'm just considering buying a new one unless I can somehow stop the leak? I found this aftermarket part on I'm not trying to spend $100 on this part.

 

best just to just replace it rather than mess with a repair. you don't have to purchase new, you can go to a junkyard and grab a non-leaking piece.