a/c compressor relay unit??

[marcus]

issue with a/c compressor clutch not activating...

i got power on the a/c button but no power being fed on the ac compressor ..fuse is ok but it seems like there might be a relay in between which toyota cant find...

anyone has a a/c diagram for our cars..??? thanks a million

[yaris2010RS]

ive seen this issue before on other cars. the clutch activating is after it checks sensors.

make sure you ac system is charged as in a discharged system will not allow the cluch to activate.

[CTScott]

As I mentioned in your other thread - There is no relay! The AC ECU drives the compressor clutch via a FET within the AC ECU.

[marcus]

As I mentioned in your other thread - There is no relay! The AC ECU drives the compressor clutch via a FET within the AC ECU.

so me not getting power on the compressor maybe sensor issue then.. 3 guys in toyota cant figure it out but they did check the ac fluid was full cant do compression check without the compressor spinning...

[CTScott]

so me not getting power on the compressor maybe sensor issue then.. 3 guys in toyota cant figure it out but they did check the ac fluid was full cant do compression check without the compressor spinning...

Did they actually plug the TechStream tool in and see what the AC ECU has to say?

[marcus]

Did they actually plug the TechStream tool in and see what the AC ECU has to say?

they wont do it unless the a/c button is blinking..which is not. would an obd reader give me a code i think my frind has one..

[CTScott]

they wont do it unless the a/c button is blinking..which is not. would an obd reader give me a code i think my frind has one..

Only a TechStream will communicate with it. A regular OBDII scan tool doesn't have the protocol info for the Toyota specific diags.

There is no flashing error light mode for the AC. I know first hand, as I have and AC ECU running on my test bench that I talk to with my TechStream tool and my YarGauge. It has about 6 DTCs logged, since it has power and CAN comm connections and the only sensor connected is the ambient temp sensor.

Do you have another dealer you can work with, since it seems like the service people at this one don't have a clue as to what they are doing.

[marcus]

Only a TechStream will communicate with it. A regular OBDII scan tool doesn't have the protocol info for the Toyota specific diags.

There is no flashing error light mode for the AC. I know first hand, as I have and AC ECU running on my test bench that I talk to with my TechStream tool and my YarGauge. It has about 6 DTCs logged, since it has power and CAN comm connections and the only sensor connected is the ambient temp sensor.

Do you have another dealer you can work with, since it seems like the service people at this one don't have a clue as to what they are doing.

ok ill try that......thanks

[CTScott]

And to double confirm that - Crashy has no AC compressor, but has everything else hooked up and her's doesn't flash either.

[yaris2010RS]

did u try reading the ac clutch wires to see if voltage is getting to the clutch?

[marcus]

did u try reading the ac clutch wires to see if voltage is getting to the clutch?

no power running so i need to trace that wire since fuse is ok.. it could be sensor good thing its already cold....we shall see

[YarisSedan]

I beleive there is a pressure sensor that detects if the refridgerant is low it will not allow the a/c compressor to engage.

[CTScott]

Per the service manual, it could be any of the below, which is why he really needs to have someone plug in a TechStream tool to narrow it down:

A/C Fuse
Refrigerant pressure
Compressor and pulley
Air conditioning pressure sensor
Evaporator temperature sensor
Air conditioning amplifier
ECM
CAN communication

[marcus]

hey ctscott..im barrowing a techstrem next week incase we cant figure out how to test my a/c issue ...any tips?? thanks im actually betting its the ambient temp sensor but we shall see..

Per the service manual, it could be any of the below, which is why he really needs to have someone plug in a TechStream tool to narrow it down:

A/C Fuse
Refrigerant pressure
Compressor and pulley
Air conditioning pressure sensor
Evaporator temperature sensor
Air conditioning amplifier
ECM
CAN communication

[CTScott]

hey ctscott..im barrowing a techstrem next week incase we cant figure out how to test my a/c issue ...any tips?? thanks im actually betting its the ambient temp sensor but we shall see..

Just hook it up and see what it says. Checked the stored DTCs first (which it will display as soon as you go into the AC section).

[marcus]

do i hook it up then start the engine or just turn the key on on acc mode...?? thanks

[CTScott]

do i hook it up then start the engine or just turn the key on on acc mode...?? thanks

You can hook it up and switch the key to "ON" to start with. You don't have to have the engine running to read the DTCs. Once you see what the codes are, then you can start the engine and attempt to engage the AC, while watching the "data" from the AC ECU.

[marcus]

got it thanks!!!

[marcus]

ok tech stream has been plugged and got code b1423 which is referring to pressure sensor.. there could be a couple of thing that can be wrong but this doesnt pin point the issue.. cant check pressure since compressor wont turn on might need to jump it.. where to start???

[09sedan]

Replace the pressure sensor?? Lol :tongue:

[marcus]

Replace the pressure sensor?? Lol :tongue:

im pretty much going this route... 1 step at a time.. sigh

[ADRIAANX]

got one for u how can i get it to u

[yaris2010RS]

before replacing the pressure switch try to jump it and create a false pressure reading. Did this on a Ford F550 once. as long as the yaris is a Normally open switch it should create the false reading.

[CTScott]

before replacing the pressure switch try to jump it and create a false pressure reading. Did this on a Ford F550 once. as long as the yaris is a Normally open switch it should create the false reading.

It is not a switch, but rather a pressure transducer. To bypass it you would need to provide the correct resistance for the pressure you are trying to emulate.

[yaris2010RS]

^thats disapointing......

Marcus, I just the date your original post, how did it end up going?

[07HBYaris]

I have an 2007 hb yaris, and my ac went last summer ('12)and still is. My ac problems are exactly as Marcus's. I am wondering if you got any progress?

My friend and his avionics teacher checked my ac out and the guys told me that I have a faulty compressor clutch.

I read a post about a 2000 echo ac compressor started working by removing a spacer from the pulley. but that car's seven years older.

[marcus]

sorry i never tried to fix mine mostlikely its the high pressure sensor but try jumping the compressor directly off the battery if it works then its not the compressor.. mine did so im shooting for the high pressure sensor which i do have but requires to vacuum the line to install it....good luck..

[07HBYaris]

Thxs for the reply. can you give me a few pointers to connecting the battery straight to the compressor? This summer hasnt been to bad yet so I'm still good to figure it out myself.

[07HBYaris]

So I got my ac looked at again. The shop hooked it up to an ac machine and it worked once. Next they replaced the expansion valve. That didn't do anything. They checked a lot of the electrical stuff but to no avail. They are pointing to ac compressor now. The above posts claim that there is no relay for the ac compressor but I was looking on rock auto and there is one for it under relays....

[CTScott]

So I got my ac looked at again. The shop hooked it up to an ac machine and it worked once. Next they replaced the expansion valve. That didn't do anything. They checked a lot of the electrical stuff but to no avail. They are pointing to ac compressor now. The above posts claim that there is no relay for the ac compressor but I was looking on rock auto and there is one for it under relays....

There is a relay for the blower, but not for the compressor. The compressor is directly driven by the AC ECU.

With them saying the compressor is bad, do they think the clutch is not pulling in, or is it pulling in, but the compressor does not create pressure?

You can do a quick test of the compressor by applying 12V to the green wire of the compressor. I would not run it for long that way, but in 30 seconds you should be able to see if it then generates cold air. If it does, then I would say that the AC ECU is bad.

[marcus]

update on my issue... recently went to ac service and was told its completely empty..refilled it with dye but still no leak showing its been 2 weeks and i still got a/c,, how long does it take to lose the ac if its leaking..i figured it should be gone in a week..

[CTScott]

update on my issue... recently went to ac service and was told its completely empty..refilled it with dye but still no leak showing its been 2 weeks and i still got a/c,, how long does it take to lose the ac if its leaking..i figured it should be gone in a week..

With a slow leak it can take quite a while. I had a car that would lose its charge over the winter, but once recharged in the spring, it would be fine until the fall.