Phoenix88

My climate control fan speed doesn't work anymore for some weird reason, just stays at max... you can change the speed on the unit, but the fans still blow hard. I took it to the dealership, they said there is a resistor that is probably blown, 100 bucks for the part!! :eek: and an hour for labour (at most). Just letting people know incase they have a problem like that, or if anyone has had a simular problem if there are any alternatives. Thanks!

mjr24

Yep, 99% chance its a resistor. That was a big problem in E34 5 series BMW I have...part was $200 though
The obvious symptom will be it only blows on max speed the whole time and really doesnt blow at all on the other speeds.
I suppose you could try some soldering on the resistor, but I dont know what the Lexus SC one looks like.

mjr24

Oh by the way, Phoenix and PCMW, thanks for help on seat...sure enough it was that lousy plastic screw, and now everything works fine again.

wwest

Lexus uses a power transistor to drive the blower motor at various speeds except full speed, then there is a relay that bypasses the transistor to supply full voltage.

Stuck relay contacts would be my guess.

Phoenix88

So are you saying that I might not even need the parts? Or might not even need to send it to the shop for that matter?

wwest

Speaking for the 92 LS400 there is a power transister "module" mounted on the climate control housing near the blower itself. It's that transistor that supplies the power for the blower unless the ECU commands max speed and then it activates a relay to overcome even the minor level of voltage the transistor would still drop at saturation.

Find someone with shop manual for your car and have them tell you where the relay is located.

Phoenix88

Thanks for the replys, the dealership has ordered the part, says it goes somewhere int he glovebox? Does anyone have a manual, I might just want to do it myself, they say it will take them over an hour which is gonna be an extra 100 bucks, normally I wouldn't care but I am back in school and honestly I could use that money for springs and shocks . If anyone w/ a shop manual can help me out that would be greatly appreciated! Might help someone in the future as well.

Thanks

Taka

transistor in A/C unit? I have extra working A/C unit, if you want...but I guess too late :P

Phoenix88

I don't need a whole A/C unit, its just a 100 dollar part that is broken... I just was wondering if anyone w/ a manual could help me find where it goes by posting some schematics for the climate control unit. Thanks though.

London Bill

There are two electronic components controlling the fan speed (three actually if you include the A/C Control Unit), the Blower Resistor and Power Transistor, both located immediatly behind the glove box, I hope your dealer has diagnosed and ordered the correct unit.

Phoenix88

Well its not the resistor for sure, I am trying to test the power transistor but can not find it. Anyone have any ideas? I will post pictures of what it looks like w/ what I am looking at. It is driving me nuts now only having the fans at full speed. Thanks again everyone.

London Bill

I have never had to do this so I can only go by the Lexus manual,
it seems you have to remove the A/C Unit (the big part behind the glove box) to get at the transistor (it must be located inside the unit, in fact the diagram above would suggest this).

But the manual on A/C Unit removal says; "Remove Engine" surely not !!!!

Phoenix88

So maybe behind all this junk?

Phoenix88

Or maybe it is below here? This is what I thought when I was looking at this picture.

Phoenix88

These are the directions I have...

POWER TRANSISTOR
Removal & Installation
Remove glove box. Remove screws and power transistor. To
install, reverse removal procedure.