LX450 a/c amplifier bypass/delete method?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

flyinbrian

flyinbrian

@brian_and_the_car
10 Year 15 Year
Joined
Apr 17, 2008
Threads
12
Messages
54
Location
Santa Barbara, CA
Hey gang!

Merry Christmas!

My a/c amplifier became a water holder with our last rain (yay, another project!), and after looking at prices for discontinued a/c amplifiers, I want to just eliminate that whole operation.

Switching to M on the back of the control unit does nada in my case, so I'm curious, now what?

Can you switch to a Landcruiser control unit that doesn't have the auto function? Just grasping at straws as electricals isn't my passion...

Thoughts appreciated.
 
flyinbrian said:
Hey gang!

Merry Christmas!

My a/c amplifier became a water holder with our last rain (yay, another project!), and after looking at prices for discontinued a/c amplifiers, I want to just eliminate that whole operation.

Switching to M on the back of the control unit does nada in my case, so I'm curious, now what?

Can you switch to a Landcruiser control unit that doesn't have the auto function? Just grasping at straws as electricals isn't my passion...

Thoughts appreciated.
Click to expand...
I’m wanting to do the same…did you figure anything out on this? My collectors edition has auto also
 
Thundercloud Cruiser said:
I’m wanting to do the same…did you figure anything out on this? My collectors edition has auto also
Click to expand...
I ended up sourcing another controller and switched it. It works, but I hate being tied to doing it again the next time my windshield leaks.
Keep me posted if you or anyone else finds a workaround!
 
flyinbrian said:
Hey gang!

Merry Christmas!

My a/c amplifier became a water holder with our last rain (yay, another project!), and after looking at prices for discontinued a/c amplifiers, I want to just eliminate that whole operation.

Switching to M on the back of the control unit does nada in my case, so I'm curious, now what?

Can you switch to a Landcruiser control unit that doesn't have the auto function? Just grasping at straws as electricals isn't my passion...

Thoughts appreciated.
Click to expand...
Is the “M” on the back of the AC / Heater control panel in the center cluster? Just wrestled the amplifier out and it looks pristine…..
 
SucioP said:
Is the “M” on the back of the AC / Heater control panel in the center cluster? Just wrestled the amplifier out and it looks pristine…..
Click to expand...
Yes, if I remember correctly that is where that switch is. It didn't help my situation to bypass the amp, that's why I got a new one.

So far so good.
 
I am having an issue with the LX450 AC control panel.

The top line with the mode switches works. I can hear the motors running setting the valves, all lights work too.

On the bottom line with the blower-outputs, I get no blower activity. Lights work.

On the middle line with the buttons "A/C", "Auto" and "Interior/Ext", there is no functioning at all. No lights. The "AC" button is just a momentary switch, same as the 'Int/Ext' switch. The 'Auto'-switch just brings all other switches mechanically back to neutral and should off course do auto A/C.

In the LX450 FSM I did not find any fault finding. In the Toyota manual there is no 'Auto' function.

Anyone any suggestions?
 
Anyone has the AC system amplifier for sale? P/N 88650-60210 or 60211 or 60112.
 
I see several on eBay for around $500. Its common for these to suffer water ingress if there is a windshield leak. Take it apart and examine the bottom of the circuit board for corrosion. Sometimes a good cleaning resolves issues. I drilled a hole in the bottom of the case to let water out.
 
I pulled the white box, 88650-60211 in my case. Opened it and all very clean, no corrosion, no burnt parts.
I have no way of testing it, but should be ok.

I still have the issue on my control panel, which is identical to others reporting their 'white box' is corroded.

Any other suggestions I could follow? Maybe pressure in the AC-system is low, don't know. Does this have the same effects on the control panel?
 
Ronald Rooij said:
I am having an issue with the LX450 AC control panel.

The top line with the mode switches works. I can hear the motors running setting the valves, all lights work too.

On the bottom line with the blower-outputs, I get no blower activity. Lights work.

On the middle line with the buttons "A/C", "Auto" and "Interior/Ext", there is no functioning at all. No lights. The "AC" button is just a momentary switch, same as the 'Int/Ext' switch. The 'Auto'-switch just brings all other switches mechanically back to neutral and should off course do auto A/C.

In the LX450 FSM I did not find any fault finding. In the Toyota manual there is no 'Auto' function.

Anyone any suggestions?
Click to expand...
Is this a new problem?
Were you or anyone else doing anything with the dash or any electrical before this problem occurred?
On the LX450 the auto climate control system has 5 associated fuses. Have you checked all of these with a meter before replacing parts?
 

Attachments

Thanks for your reply,
yes, I tested all fuses. Do not know what the 10A gauge is, but I assume the fusible link. Measured that one too on resistance and it seems ok to me. I do not understand why they used a wire for this instead of a fuse, but I have a new one and can replace it to be sure.

Since all lights except the middle row in the control panel light up and I can also hear the motors run when changing modes, I expect the control panel to be ok.
I have replaced all the leds inside for brighter ones some time ago, but as I can remember this was before the AC stopped working.
Last time we used the car was end of 2023. We were having AC issues then too, but they are traced back to not enough cooling fluid in the engine and engine temp rising above 226F which stops the AC.

Anyway, I have removed the control panel and tested it. Top and bottom row are according FSM/EWD. The AC en Recirc buttons are momentary on the LX450 so I do not know how to test these. The control panel switch is on A(utomatic).

Put everything back together, same results.

As the symptoms are the same as described on the forum when the white control box (in my case 88650-60211) is corroded inside, I have removed it for inspection. Circuit-boards are clean, no corrosion, no burn marks. Made some holes in the bottom of the box just to be sure and sprayed the contacts.
Built back again, same result, no AC, no blower, no lights in the middle row of the control panel.

I'll replace the fusible link first, probably not solving anythng, but just to be sure.

What next steps to take?
 
I replaced the fusible link, no result.

Tested again all 5 fuses (10A Gauge i one of them, my mistake). On 4 fuses I get 12 volts at both sides of the fuse.
On the AC fuse I get 0 volts, which could probably be explained by the missing signal from the automatic amplifier.
 
Ronald Rooij said:
On the AC fuse I get 0 volts, which could probably be explained by the missing signal from the automatic amplifier.
Click to expand...
A12 pin 11 on the AC Automatic Amplifier is what throws the HEATER RELAY and powers the AC fuse.
Before replacing parts I would make sure all fuses/relay/signals/connectors are secure and working.

This system is downstream of the 3 fusible links. If one of them were faulty, you'd have other issues.
 
Ok,
I replaced the fusible links for new ones. I had this one as spare.No change.

Removed the black AC amplifier box behind the glove box (P/N 88650-60081). Opened it, all clean, no corrosion, no burns. Sparayed contacts of the connector just to be sure. No change.

Removed the AC automatic amplifier again P/N 88650-60210). Opened it again. On close examination there was some dust contamination on one IC. Removed by blowing. Installed again, no change. I have another unit coming next friday from the HZJ81 anniversary.

Removed the Heater main relay. Tested it acc manual with and without 12V. All ok. Installed again. By switching on the key you do not feel it 'clicking', so it is probably not powered by the AC automatic amplifier.

I will now remove the control panel again to see if I have forgotten to connect any of the sensors. Think not, but just to be sure.

Any suggestions for checking, shorting sensors to see if these are ok? The amplifiers are totally without a clue for me what should be working and what is not required to have the A/C, AUTO and Recirc buttons to lit up and to have the fan blowing.
 
I studied the wiring diagram for the AC automatic amplifier. I think I am beginning to understand how it works. This computer decides to run the AC, blower, modes based on sensors and buttons pushed at the control unit sort of management layer. The rest of the amplifiers are there to do the real work and safeguard overload situations.
Probably someone absent or sick at management-level. Friday I have some new management from FZJ81 flown in, hope that solves the issue.
-----
Checked again the Gauge Fuse. This one has 12V on both sides. There should be 12V on pin 3 of the main heater relay, which I have.
There is also 12V at pin 1 of the main heater relay.hard
To me it seems that neither current from the Gauge fuse nor the FL Fuse powers the AC automatic amplifier. The amplifier just switches the relays for these currents.

It looks to me as if the ECU-B and/or the CIG-fuse powers the AC automatic amplifier (fuses are ok). The amplifier switches to ground to activate AC-compressor, Blower etc. There must be a working Ground connection at the amplifier since some of the lights in the control-unit are lit and there is only 1 pin connected to ground.
Top and bottom row led's are more or less hard wired through the amplifier, same as the mode-selection on the top-row resulting in that mode-selection functions.

Middle row leds are controlled by the amplifier. Bottom row leds are also more or less hard-wired so they lit when the button is pushed.
Blower function, AC, AUTO and Recirc functions are controlled by the amplifier.
Activation of the AC is protected by several sensors and also the auto-function uses several sensors but I do not understand that these should restrict the blower function.

My conclusion so far is that although the AC automatic amplifier looks like new inside it is probably broken. No way to test and repair it, but I will look into it as these units are pretty expensive.
Nobody out there who has tried to put the logic in a 8$ Arduino?
 

​

R

Thread 'LX450 Air Inlet Servo Issue RESOLVED'

I'm the new owner of a moderately neglected but not abused or modified 1997 LX450 w/lockers. I've been lurking here for a year and working on the normal issues with these... the info here has been great!
I have something to add now that may be of interest to those with the automatic climate control:
My air inlet (fresh/recirc) vent would cycle continuously when in RECIRC..worked ok in FRESH.
I began by taking out the servo and checking the limit switching tracks which stop the motor in the right place..I tested it on the bench with a 12v battery and it worked as it should. I then checked...
  • Like


A bit more info on the Auto AC amp board.
 
Thanks, that really helps I think. I have not followed the traces on the board yet, but anyway I have ordered 5 transistors and I will just replace them all. I will test each of the ones removed just to check.
If this is the solution it really would save a lot of money and it is an easy repair or maybe call it preventive maintenance.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom