AC controls partially dead

[htony1]

Last week, out of no where the AC in my 97 LX450 stopped working on each fan speed but HI. When you press the high button it works fine but each of the low - medium controls isn't working. So I searched through the forums and read about the AC amplifier above the gas pedal being the potential culprit. I finally had 15 minutes on Sat. to take it apart and the amplifier looks good, no corrosion, or evidence of ponding water / condensation:

Any ideas on what could be the issues not? Relays? Do i need a new AC control unit?

Also, since I have owned the LX450, the light on the recirculation button does switch although the button seems to be working properly in all other aspects. could that be a symptom of the same issues?

Looked like this:

 

[Pin_Head]

The Lexus FSM has an extensive troubleshooting guide for A/C (and everything else), which you probably don't have, since you are asking this question.
The top 4 possibilities according to the FSM are:

No blower control:
1. AC control assembly
2. Extra-Hi relay
3. Blower resistor
4. Power transistor

Each has a link to the page in the FSM of how to test each component.
If the speed indicator lights do not light up when pressed, then it is likely the control assembly.

 

[htony1]

The Lexus FSM has an extensive troubleshooting guide for A/C (and everything else), which you probably don't have, since you are asking this question.
The top 4 possibilities according to the FSM are:

No blower control:
1. AC control assembly
2. Extra-Hi relay
3. Blower resistor
4. Power transistor

Each has a link to the page in the FSM of how to test each component.
If the speed indicator lights do not light up when pressed, then it is likely the control assembly.

Thank you for that answer, sounds like a need a FSM

The speed indicator lights do light up when pressed. I unplugged the Amplifier Assy, Air" Toyota P/N 88650-60130 - Denso 077800-0111 at the suggestion of the author of this thread https://forum.ih8mud.com/threads/fan-blower-motor-resistor.38698/. It allowed him to regain control over the low setting. unplugging this did not help my case though

 

[Pin_Head]

The lights lighting up are only part of the test, so it still could be the controller. The amplifier is not a suspect for this fault.

Here are some cell phone pictures of the test procedure for the controller

 

[htony1]

Thanks for those pics, the actually helps with the situation at hand and another one about switching from auto to manual mode

 

[blkprj80]

Check the connector that goes sideways into the blower box behind the glove box. Look up from underneath with a flashlight.
Chances are one of your passengers kicked it and it broke or came loose.

 

[canman]

Haven't really checked the FSM, but no low or med speed would have me looking at the resistor and assc wiring.

 

[htony1]

Well, I just pulled the glove box out, unplugged the blower resistor and plugged it back in. Then I followed the wiring up to the blower box to check for burnt our wires. Presto, the AC starts working on all speeds again. So most likely it came unplugged or its a faulty part. Thanks again for the help and I will update this post after riding around and see if it stays operable.

this is what the connector looks like, located just behind the steel crossbar the glovebox mounts to.

 

[htony1]

Well the problem is back. I unplugged the resistor mentioned above and plugged it back in and it didn't get the low-medium 2 back in operation. I am lost again but noticed the left silver circular thing in the attached photo, which I think is a resistor was very hot.

 

[blkprj80]

The silver things are relays.
It is possible you have a relay with bad contacts, which could cause it to run hot.

Since it came and went when you unplugged and reconnected the resistor connector, I'd suggest pulling the resistor assembly out and checking it under load. Beware, it will get hot. That's why it is located in the air tunnel.

 

[Pin_Head]

Here are the FSM pages covering the resistor, relay and power transistor. Note that there are two blowers, front and rear and they have different resistors. The front resistor is inside the evaporator assembly and requires its removal. It is not shown here.

 

[htony1]

Pin_Head, Thanks again for the help. My truck has the rear heater removed by the PO. I need to track down the front blower resistor now......

BTW, where did you get your FSM?

 

[Pin_Head]

I bought it from Toyota publications on line for $110. AC is one of the few things that is different on the LX450 vs the FZJ80

 

[htony1]

well a few weeks out and low - Medium 2 speeds work intermittently. I came back from a trip and the cruiser sat up for 3 days and all speeds were working like a champ for a day.

i forgot to mention that prior to this the fan made a whining sound but I do not hear it when it blows high. Maybe thats because is working so hard. I don't know which part to replace first, can't afford them all. The kids are either too hot or too cold

 

[htony1]

mild update,

Took the cruiser to a local shop who does quality work to get an axle seal and valve cover replaced, and they replaced a AC resistor (don't know which one) but now I low and High. better than high only. However low, med 1, and med 2 blow at the same speed... any thoughts?