AC Inoperable, collective wisdom of mud help (1 Viewer)

[flintknapper]

Did a little bit more research. It seems that Toyota uses a 5V reference circuit for sensors for many of its vehicles (like many other manufacturers). Not sure if that also applies to the LC platform, but it probably is a good guess.

That means that you should read +5V between the pins of outside air temperature sensors with the sensor unplugged. Maybe also when plugged in, but that is difficult to know without knowing the circuit diagram of the A/C control system.

Verifying the +5V would be a quick way to see if the A/C control amplifier is at least up and running.

This is worth watching, for those of you who want to know more about sensor grounds and reference voltages:

^^^^^

Agree with this route. Well thought out. Would eliminate a large portion of the circuitry being the issue.

 

[jerryb]

Trip the relay with techstream without the engine running. Without that engaging you will get all the ac diagnostic codes in the check menu.
The AC amp is in the black box all by itself attached to the back of the nav unit. It should never fail. should..
Before I spring for a new fuse box off partsouk I'd verify how the AC plugs look in the back (3) and the nav plugs (3) and like you said, clean up the lower cowl box.

But if the computer can't trigger the clutch relay there isn't much to do but take the main fuse box out and have a look at the relay. Even if the AC amp you have is the wrong one techstream will still trigger the clutch. You just wouldn't get a signal with the wrong amp.
I Was thinking maybe if you somehow had a newer, wrong AC amp, probably not though.


It would be good sign if techstream does trigger the relay. Then you could move on to the other fuse box and wiring.
Maybe someone else said it already but I think my static equalized readings are around 100 +

 

[white_lx]

I'll need to get better understanding of where to test circuit of OAT sensor. The owner said it is a working replacement sensor, so for now I'll assume is. So somewhere between sensor and display input is shorted. I've suspected all a long, it is all related to the same issue.

I also believe the sensor is fine. By testing the voltages at the sensor you can narrow down the search a lot, without opening anything as the sensor is conveniently located under the hood. Think of it as a convenient probe into the internals, available right there.

Is the AC Amplifier in the NAV unit?
If so, I can safely assume "for now" that it's working fine. As it been replaced twice. That is, provide it's not being damaged by short elsewhere each time a replacement was installed.

According to the diagrams they are two different items.

 

[flintknapper]

Trip the relay with techstream without the engine running. Without that engaging you will get all the ac diagnostic codes in the check menu.
The AC amp is in the black box all by itself attached to the back of the nav unit. It should never fail. should..
Before I spring for a new fuse box off partsouk I'd verify how the AC plugs look in the back (3) and the nav plugs (3) and like you said, clean up the lower cowl box.

But if the computer can't trigger the clutch relay there isn't much to do but take the main fuse box out and have a look at the relay. Even if the AC amp you have is the wrong one techstream will still trigger the clutch. You just wouldn't get a signal with the wrong amp.
I Was thinking maybe if you somehow had a newer, wrong AC amp, probably not though.


It would be good sign if techstream does trigger the relay. Then you could move on to the other fuse box and wiring.
Maybe someone else said it already but I think my static equalized readings are around 100 +

^^^^^

Correct. For an ambient of about 90°F and adjusting for the elevation in Denver...that would be in the ball park.

It would confirm that there is some amount of liquid refrigerant in the system and that the pressure is enough to allow the binary (low pressure side) switch to close and provide power to the clutch.

When troubleshooting possible electrical gremlins (the most likely cause here), I like to work it backwards from the compressor. Establish that the clutch itself will engage (even it has to be bypassed) and that the refrigerant charge is sufficient to test. Also the compressor has a 'lock out' feature that detects discrepancies in engine speed and compressor speed. It will disable the compressor in order to save the serpentine belt if a certain rpm difference is detected. The lock out sensor can be OHMed out.

Once it is established the compressor and charge (static) are OK, then checking the connections and wiring back to the pressure switch should be done. You can think of it as the last 'leg' in the circuit. If nothing wrong is found there...then the fun begins.

At that point we want to move inside and start checking all the cabin controls, sensors, wiring, etc....starting with the most common faults or going directly to 'historical' issues if the vehicle has been worked on before (service history).

 

[2001LC]

As mentioned in thread. I did confirm the magnetic clutch works by jumping with + from battery and got 800 OMS at 90F on lock at compressor (FSM spec ~500-1000 at 68F)

Trip the relay with techstream without the engine running. Without that engaging you will get all the ac diagnostic codes in the check menu.
The AC amp is in the black box all by itself attached to the back of the nav unit. It should never fail. should..
Before I spring for a new fuse box off partsouk I'd verify how the AC plugs look in the back (3) and the nav plugs (3) and like you said, clean up the lower cowl box.

But if the computer can't trigger the clutch relay there isn't much to do but take the main fuse box out and have a look at the relay. Even if the AC amp you have is the wrong one techstream will still trigger the clutch. You just wouldn't get a signal with the wrong amp.
I Was thinking maybe if you somehow had a newer, wrong AC amp, probably not though.


It would be good sign if techstream does trigger the relay. Then you could move on to the other fuse box and wiring.
Maybe someone else said it already but I think my static equalized readings are around 100 +

I did not know I could tiger with engine off. I'll give a try.

I also believe the sensor is fine. By testing the voltages at the sensor you can narrow down the search a lot, without opening anything as the sensor is conveniently located under the hood. Think of it as a convenient probe into the internals, available right there.



According to the diagrams they are two different items.

The owner placed a bag in the truck with NAV and called it AMP. I'll look and see if AC AMP is on back of it. He and Toyota have likely used the correct ones in the two times they've replaced, but that would need verifying.

This rig is built with iron front bumper. It's blocking access somewhat to both OAT & pressure sensors.

If I can get to OAT sensor. How do I test that. Do I pull off it's wire housing block and test between leads or lead and frame ground for 5V. I'd assume IG key need to be on?

 

[2001LC]

Okay, so did following at OAT of ~74F which is ~ what condenser temp read with IR temp gun. Elevation 5,250 ft ASL.
Looks okay for static test doesn't it?

As noted earlier I tested magnetic clutch by jumping with 12 volt as check lock with OMS meter all meet FSM spec. I then tested trough tech stream and clutch again checked good, as it locks. But here's something interesting. Someone cut hole in fuse box.

As I run magnetic clutch in tech stream test, I see/hear a spark every few seconds. While magnetic clutch holds steady (locked).


As noted earlier, I've extra NAV screen Toyota PN# 86111-60250. Now that I've looked in the bag of parts. I see I've two Denso black boxes of same part number Toyota 88650-60851 amplifier

I tested ambient air sensor. I could see tooling marks indicating it been removed before. Confirmation it had been replace as I was told.

I also check wire and found one lead 0V the other ~3.49V

So looks to me as if everything checkout that been recommended above. Anyone see anything a amiss or did I missing anything?

So it was as I assumed and was told. But better to check then assume everyone before did their job.

 

[2001LC]

So I moving on and pulling the RH J/B fuse box. By the looks of it, it's not been removed before (good sign I suppose)

But I can't see anyway to remove without pulling all CPU behind glove box, fan along with fan housing. The fan housing looks tough. I'd like a workaround if anyone has one.

Anyone know how to get RH side junction box (fuse box in RH side cowling) out?
Anyone seen in FSM they can point me too?

There is about 4" to 6" more of box hidden behind fan housing, along with lots wires and wire housings blocks going into J/B and above it.

 

[flintknapper]

Static pressure is just right and the fact that you previously checked the clutch for operation and ohm'd the lock out feature...let's us check those items off the list.

So that puts us searching for two things.

1. Reasons why the system will not 'call' for activation (sensor/ecu related).
2. Reasons why the signal/current is not reaching a component. (electrical circuitry).

 

[white_lx]

The arcing looks like flyback of the inductive A/C compressor clutch. I would expect to see something like that at each 'off' cycle, assuming the clutch has no flyback diode arrestor built in? If you only see it when using Techstream, it is probably an artifact of Techstream very briefly switching the clutch on/off. Wondering if the access hole was created while trying to diagnose this problem.

As noted earlier, I've extra NAV screen Toyota PN# 86111-60250. Now that I've looked in the bag of parts. I see I've two Denso black boxes of same part number Toyota 88650-60851 amplifier

That 88650-60851 is the A/C amplifier (aka controller).

I test ambient air sensor (found big opening at side of bumper) made for easy access. I could see tooling marks indicating it been removed. Confirmation it had been replace as I was told.
I also check wire and found 1 lead 0v the other ~3.49v

So you measured between one pin and chassis ground and found 3.49V? I was expecting +5V based on some other Toyota vehicles. But maybe this platform is different. But it shows that the A/C amplifier is alive. You probably have 2 other good ones there as they were never faulty when replaced.

I quickly checked the voltage of my '00 LX and it was 3.22V with the sensor disconnected. Not sure if that is a relevant difference, but I would expect it to be more consistent given this being a 'reference' circuit.

The difference could be the bad FRSG or amplifier ground. This can be verified by measuring the voltage between the '0V' pin of the temperature sensor and chassis ground (key on). I did this and found 31mV (0.031V), indicating a good FRSG ground. Can you verify this on your vehicle? Make sure to put the multimeter in the lowest DC voltage range (2000 mV?) Anything over 50mV or so becomes 'suspicious'. Pay particular attention to any fluctuation of the voltage as well.

 

[abuck99]

Awesome thread- sub’d

 

[jerryb]

You guys are above my pay grade, but I couldn't live with that fuse box. Someone tried to "fix" that before.

 

[2001LC]

Static pressure is just right and the fact that you previously checked the clutch for operation and ohm'd the lock out feature...let's us check those items off the list.

So that puts us searching for two things.

1. Reasons why the system will not 'call' for activation (sensor/ecu related).
2. Reasons why the signal/current is not reaching a component. (electrical circuitry).

I tried to get wire block off pressure switch. But just can't get around it without removing some shield. I'll come back to it later. I'll just concentrate on RH J/B block (fuse box) for now. My instincts say "that's the area to be in".

The arcing looks like flyback of the inductive A/C compressor clutch. I would expect to see something like that at each 'off' cycle, assuming the clutch has no flyback diode arrestor built in? If you only see it when using Techstream, it is probably an artifact of Techstream very briefly switching the clutch on/off. Wondering if the access hole was created while trying to diagnose this problem.



That 88650-60851 is the A/C amplifier (aka controller).



So you measured between one pin and chassis ground and found 3.49V? I was expecting +5V based on some other Toyota vehicles. But maybe this platform is different. I quickly checked the voltage of my '00 LX and it was 3.22V with the sensor disconnected. Not sure if that is a relevant difference, but I would expect it to be more consistent given this being a 'reference' circuit.

The difference could be the bad FRSG or amplifier ground. This can be verified by measuring the voltage between the '0' pin of the temperature sensor and chassis ground (key on). I did this and found 31mV (0.031V), indicating a good FRSG ground. Can you verify this on your vehicle? Make sure to put the multimeter in the lowest DC voltage range (2000 mV?) Anything over 50mV or so become 'suspicious'.

First let me say: Your statement in post #10 and @Njck22 follow up stating "it does connect all the dots" Is right wear my instincts take me.

I wasn't very concerned with spark. I'll bet your right and it's tech stream cycling. Hole in engine fuse box and so many other things I'm finding sure indicate their been a lot of man hours hunting for this issue, by many from all accounts.

I'm not liking, wasting my time going back over all they've done, but I must!

Thank you so much for going out to your rig and verifying that 3.49V at temp sensor pin. I'll need to go back and check the '0' pin as you did. I did check while in there, in many different ways. Just don't recall what I got.

Awesome thread- sub’d

Always nice to have you around! Stay awhile!

You guys are above my pay grade, but I couldn't live with that fuse box. Someone tried to "fix" that before.

I hear you Jerry. But I don't think anyone got into fuse box. They certainly did not try to remove it. Nor did they pull the fuses I did.

I'll need to look at one of my other rigs. But looks like this dash has been glued, about 3" below my finger. There are other signs of work in the area.

 

[jerryb]

Evap replacement.
It's funny though, they knew exactly where to cut to have a look at that relay.

 

[white_lx]

Seems like this vehicle has some history. Too many cooks?... Hope the sketch below makes sense.

 

[2001LC]

Evap replacement.
It's funny though, they knew exactly where to cut to have a look at that relay.

My first thought as well. But look at the thick black wire. It still has foam, which one would think they'd loose replace evap! Also screws on cover look untouched. But as good a job of gluing, they knew their stuff. The damper for glove box lid 'loop' had be pulled out and latch had missing bolt, which keep lid from closing properly. Owner gave me with glove box out, so he'd been in here. Also ECU screws appeared to have been removed. Was this all hunting for AC issue, likely.
But yes many 'cooks' behind this glove box.

Which relay?

Seems like this vehicle has some history. Too many cooks?... Hope the sketch below makes sense.

View attachment 2029222

Not sure.
Does the temp sensor connect to air mix servos through RH J/B block; +, relay, signal ground, etc. in any way?

Servos aren't working either. Only passenger has been complaining winter cold air in from foot well. Dampers are open to heater core, or at least some. As it blow hot, not just warm.

The door for fresh is partially open. Seems it should be full open or closed. Possible this short happen in mid stream. Clues..

 

[2001LC]

Having hard time getting J/B block (fuse box) out. I've loosen the top nut after pulling most wire block and gotten a lot out of the way. But if I pull that top "nut" I'll not be able to get it back on.

That shows as a ground point, if I'm reading this correct?

I started a thread on how to remove, but no response(s) yet. RTH: How do I get RH cowling junction block (fuse box in right foot well) out?

 

[white_lx]

Not sure. Does the temp sensor connect to air mix servos through RH J/B block; +, relay, signal ground, etc. in any way?

Yes they are connected. Look at the highlighted traces in the diagram above. They are all connected.

The sensor ground for the air mix servo position feedback (shown in the middle of the diagram) is connected to all the sensors via the highlighted sensor ground. Only three sensors are shown in this diagram, but there are a few more circuits on a separate sheet.

The greyed out junction area in the right bottom corner of the schematic is located in RH cowling junction box and is also involved in this same sensor ground.

So by measuring on pin 1 of the outside temperature sensor, you are effectively measuring the signal ground level in the junction box.

 

[2001LC]

Okay. So I wasn't sure that was at J/B block, now I do.This is good news. Thanks @white_lx

There was only one fuse, the"RR AC" that I saw and picture above related to AC in the fuse block of J/B. But apparently there is connection within or parts of J/B block. This also means by the test you had me do, iv connection to the block.

I really do not want to pull the fan housing to get J/B block out.. Possible I could make a tool to reach an replace nut, as of right now, I know I can't by hand. But even then I could get into more than I've time for, I'm on day 3 now. I've got to finish Merlot this week, and I've a corroded brake control wire job coming in Thursdays. I'm going to pull and replace the very pricey brake control wire and see condition of booster motor commutator is in. Both of these, I need my shop for. If I get into a issue with pulling RH J/B Block, it could get this AC job stranded in shop for the week.

So I'm going to continue pulling all I can, cleaning fuses, loosen what I can, spray electric contact clear and HP air where I can. Just generally "stir the pot". If I'm correct and it just some oxidation/corrosion on contacts, who knows, I may get lucky with some good results. So I'll put back together once done and see what happens. If no go. I'll then need to put off until a J/b Block is found and I learn the best way to remove block. As for LH J/B block, I did not see any issues with corrosion, like stuck fuses. But if not RH than next step may be LH.

 

[jerryb]

Paul, I meant the sliced open the main box in the engine bay to have a look at the relay on the underside, the 4 relays in there attached to the main board.
They cut it open and took the cover off, I assume to see the mag clutch relay. Someone suspected that before. There's an AC sig lock wire, it's blue that directly controls that, A47 pin 21 lock.

They probably also assumed replacing the screen board, and the ac amp would fix it. Which makes some sense. Without going down the fuse box-s rabbit hole.

 

[2001LC]

Thanks everyone.

Land Cruiser just like me! HA!!!!

Cold, servos working, OAT reading as it should.

If acts up again, new RH J/B block will be best bet.

Besides all the things talked about above. I disconnect battery as I worked on J/B Block and finished be cleaning battery clamp and greasing. Battery new but clamps had oxidation. I'm not saying that fix AC. Just mention as one should always disconnect battery when working on electronic.