SOLVED !! A/C electrical problem (1 Viewer)

[kruisinkid]

So while I was out of the county for 2 months, the wife said "the heater doesnt work anymore." i just got back and found this:
-all fuses are good: AC, GAUGE, HEATER
-heater blower relay is good and can hear/feel click on and off
-unplugging the a/c amplifier has no effect
-all the indicator lights on the controller unit work
-all levels of the blower work
-all location servo motors work
-i have the vague assumption i have enough pressure in the system

the problem is the a/c, auto (this is a 40th anniv, same as a lx450) and recirc buttons dont work, but their lights work. i can get the system to come on for a tenth of a second if i hold the a/c button and if i keep holding it, it will try and turn on every 2 seconds but go right out. i can hear the blower turn on for a moment. the lights for the blower and zone all work regardless of a/c button state.

i tried jumping the pressure sensor to no avail. my plug for it only has 2 wires, across from each other, the short way.

does this sound like the a/c controller is bad? is there something else to check. i havent pulled the controller out of the dash yet. looking for other less invasive things to try first. possibly the water temp sensor?

thanks all!

 

[kruisinkid]

so maybe i was unplugging the transfer case computer? 88650-60081 on ebay comes up as lx450 transfer case cpu, but toyotapartsdeal.com says its an a/c amplifier. is the lx450 amplifier not behind the glove box?

 

[TrickyT]

Pretty sure a 88650-60081 is an A/C amp for systems that have automatic A/C (Lexus and 40th anniversary edition). Bizarre that 3 different postings on eBay claim that it's the locker ECU. The locker ECU is in the passenger kick panel, while the A/C amp is (as you say) bolted to the evaporator behind the glove box.

 

[kruisinkid]

i thought i read that the lx450 and 40th anniv had there a/c amps on the driver side kick panel but i dont see anything obvious. the cpu i found behind the glove box also did have a plug or terminals that exactly matched my 96 FSM. so i guess i dont fully believe its the a/c amp yet.

 

[inkpot]

Really dumb questions: is your heater valve working or has the cable fallen off. And are you low on coolant?

 

[TrickyT]

i thought i read that the lx450 and 40th anniv had there a/c amps on the driver side kick panel but i dont see anything obvious. the cpu i found behind the glove box also did have a plug or terminals that exactly matched my 96 FSM. so i guess i dont fully believe its the a/c amp yet.

Check out this page on cruiserparts.net: http://shop.cruiserparts.net/index.php?main_page=index&cPath=6_40_204

It shows the different A/C amps. Because the 40th anniversary edition came with automatic air it used a different A/C amp than other '97s.

 

[scrowley]

Run 12v right to compressor. See if it stays on. Always good to do this with a gauge hooked up in case pressure raises to high in ac system.

 

[kruisinkid]

Run 12v right to compressor. See if it stays on. Always good to do this with a gauge hooked up in case pressure raises to high in ac system.

where is the lug or connection for the compressor to hot wire to? that was my next direction.

 

[kruisinkid]

Really dumb questions: is your heater valve working or has the cable fallen off. And are you low on coolant?

the crappy AC Pro gauge shows about 100psi on the low side with the compressor off (i havent been able to get it on for more than .1 seconds yet). i guess i either need to take it to an ac shop or buy a manifold gauge. i believe the valve is working but havent confirmed. the system is behaving like i described no matter what temp i set it to.

 

[kruisinkid]

so i have found the a/c auto system amplifier up next to the gas pedal. its a white box and from reading other threads can become corroded internally from mild windshield leaks. i pulled the boards and cleaned up and resoldered some points on it to no avail. as soon as i get my hood cable fixed i will hot wire the compressor to make sure the clutch is working. i pulled most of the rest of dash apart in the meantime.

-how do i get the round relays off of their bases? pulling straight out doesnt seem to work. are there locking tabs on those?
-where is the magnetic clutch relay for the compressor?

my next points to troubleshoot:
-magnetic clutch
-engine temp cut relay
-water temp sensor
-thermistor (40th's have a few)
-beep out some of the connectors

anything else? i ordered the '97 LX450 EWD hoping to clarify a few things that are different to the 40th/LX450

 

[kruisinkid]

SOLVED!
it was indeed the auto a/c amplifier. there were some spots of corrosion that i cleaned up but the main culprit was a trace had burned up under some corrosion. i pointed it out in the pic. sorry i didnt get an after shot, but i sanded the trace down to the copper, added some solder on top of it and ran a small piece of solid wire (22awg) across the broken burnt off section. i just put it all back with with all the other amps and control unit to test and all a/c functions are back! i cant tell you how happy i am to not have to spend at least 450$ replacing the auto amp. whewww!

other lessons learned:
-the control unit should be the last thing to test or replace to go bad. there is almost nothing inside it but buttons, resistors, caps and LEDs. there are no logic boards or IC's. it is really only there to switch all the various relays and amps in the system. almost nothing can go bad in it.
-in LX450's, 40th's and CE's, the ECU-B and CIG fuse are also necessary in these a/c systems so thats a total of 5 fuses to check FIRST!

in my troubleshooting, i found and compiled the 97 LX450 EWD and the AC part of the 97 LX450 FSM. it took 2 hours to do both. oy. i will try and find a safe spot on the web to host them and then post a link in a later thread.

i also bought a new dryer and expansion valve so before i really put everything back together i will give the whole system a big rehab to get ready for the summer. thanks all for your help!

 

[blkprj80]

It looks like you have issues with the white 4 pin connector and the resistors directly below them. That orange stuff can't be good.

Glad you found it. Have you fixed the windshield leak yet?

 

[kruisinkid]

Nothing gets connected to the 4 pin. Its some kind of diagnostic or expansion header. A black sticker at the bottom of the case blocks it.

Silicone injections are next

 

[aviator31]

My a/c just quit me and I suspect it has something to do with washing the engine bay. I also removed/cleaned the MAF and throttle body. And I removed my main battery on DS in order to tighten my steering "bolt". I don't think it's coincidence that it quit after doing this. What fuses are you referring to(LX450)?

 

[DSRTRDR]

I suggest to host the wiring diagram in Trollhole's collection of FSMs

 

[kruisinkid]

My a/c just quit me and I suspect it has something to do with washing the engine bay. I also removed/cleaned the MAF and throttle body. And I removed my main battery on DS in order to tighten my steering "bolt". I don't think it's coincidence that it quit after doing this. What fuses are you referring to(LX450)?

AC, 40A HEATER, GAUGE, ECU-B, and CIG

edit: what doesnt work about your system?

 

[kruisinkid]

I suggest to host the wiring diagram in Trollhole's collection of FSMs

i will certainly add the link to the thread but i need a place to host them to render the link. ill see if my google drive is capable without giving everyone access to all of my files

 

[TrickyT]

SOLVED!
it was indeed the auto a/c amplifier. there were some spots of corrosion that i cleaned up but the main culprit was a trace had burned up under some corrosion. i pointed it out in the pic. sorry i didnt get an after shot, but i sanded the trace down to the copper, added some solder on top of it and ran a small piece of solid wire (22awg) across the broken burnt off section. i just put it all back with with all the other amps and control unit to test and all a/c functions are back! i cant tell you how happy i am to not have to spend at least 450$ replacing the auto amp. whewww!
...

Nice going, kruisinkid! Black Project 80 is right, though. There is other corrosion visible on that board too. So either some water got in there or one of the electrolytic capacitors is leaking. You should try to clean all that kunk out of there as it often is conductive and will cause more problems in the future. A spray can of electronic flux remover is good for cleaning PC boards like that. But if it's a leaking capacitor you'll need to replace it too.

 

[kruisinkid]

yeah there was a lot more than what that pic showed. that was when i first pulled the board. i hosed it down with contact cleaner, toothbrushed it, and reflowed a bunch of solder points to be sure. its as good as new now. hopefully the electros last another 15 years.

 

[aviator31]

AC, 40A HEATER, GAUGE, ECU-B, and CIG

edit: what doesnt work about your system?

The a/c light comes on as it should and the fan speed selector is fine, but compressor doesn't engage. No noticeable leaks anywhere and it worked flawlessly before winter.