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VX Commodore Aircon compressor not activating

Specific interior modification information for Holden Commodore VT and VX Series Commodores, and HSV models

Postby davewanna » Thu Oct 17, 2013 8:04 pm

I see there are some guru's on here, maybe someone has some information I need.

I have a VX Commodore engine in a toyota 4x4. This has a factory ECU, and a BCM Simulator on it.
The BCM Simulator has an input for A/C which I have connected to the car's A/C Circuit. It communicates with the ECU over ALDL. When the button is pressed, the BCM simulator activates the low-speed fan, but the A/C compressor doesn't engage.

What is needed for the commodore ECU to engage the compressor? The system has been gassed up today, it has factory VX Pressure transducer connected to the factory loom. What else does it need?

Cheers
Dave
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Postby TazzI » Thu Oct 17, 2013 10:00 pm

Gday Dave,

I was under the impression that the AC controller does the actual controlling of the unit. Since people that have upgraded the manual dials aircon unit to the electronic version have not needed to actually change the bcm, just the entire hvac unit and electronic climate controls.

In saying that, theres alot of stuff that the bcm looks for and displays in its broadcasting messages which would include aircon being turned on, indicators, power button, gear changes ect. Its how all the modules in the car get the information.

Your bcm simulator may be missing some required frames or you may have something wired up wrong?
Do you have access to an ALDL cable? Might be able to get you to manually send a few frames and see if that engages it? Although might not be aldl comms related.
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Postby silversv6 » Thu Oct 17, 2013 11:55 pm

It also needs the power train control module trigger, which gives the "on" signal to the compressor.4 post relay; Bat+ to a/c relay then switch side to compressor & trigger from the power train cont module Do your cooling fans (radiator) turn on when the A/C is turned on? I done a similar one (vt v6-hilux 4by) about 10 years ago & got the air con working without the PTCM. By memory I rewired the a/c comp to a new relay from the original switch, but I can't remember if the fans turned on with the a/c. Have you checked if you have power at the compressor clutch? I am sure these compressors have a pressure switch built into them which play up a fair bit. Just unplug the power wire at the compressor & plug it straight into the clutch wire. Just have a good look at the comp & you will see the plugs I'll keep racking my brain! cheers
Last edited by silversv6 on Sun Oct 20, 2013 11:13 pm, edited 1 time in total.
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Postby davewanna » Sun Oct 20, 2013 9:50 pm

Thanks guys, got it sorted finally. I am using the factory toyota stuff to tell the BCM simulator to turn on, it was turning on the low-speed fan, but the A/C never engaged. Turned out to be a non-existant relay but that's now sorted.

I found the the BCM controls the low-speed fan, and sends an A/C request signal to the ECU, it checks line pressure, coolant temp, RPM, and a couple of other things, and when all is ok, it engages the A/C clutch. It also tells the BCM to turn off the low-speed fans once road speed is over about 30kph.

All working properly now, I'm very impressed.

TazzI, I do have an ALDL cable, and use EFIlive to view the information. What program would I use to send frames? and is there a description of the ALDL protocol somewhere I can read up on? (Not for this issue, but another project)

Cheers guys

Dave
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Postby TazzI » Mon Oct 21, 2013 2:10 pm

davewanna wrote:TazzI, I do have an ALDL cable, and use EFIlive to view the information. What program would I use to send frames? and is there a description of the ALDL protocol somewhere I can read up on? (Not for this issue, but another project)

Cheers guys

Dave


Good to hear you got it sorted!

To view/send raw data, jump onto pcmhacking.net and grab the OSE tool program developed by VL400. Thatll let you see all the raw info coming over the comms and also let you send custom frames.

I suggest making sure you know what your sending over the comms sine sending random info could cause problems. Generally a test bench setup is suggest for any research or trials since would rather screw a spare part up then cripple a car!

As for a description on the ALDL protocol.. Well.. doesnt really exist except for what Wikipedia has. ALDL is not a standardized protocol, and well most of the functions/responses are hard to decipher without reversing a scantool.
Its more of a trial error situation to understand whats being done, the modes that are being used and what each byte in each frame means.

Let us know if theres anything in particular about the ALDL protocol that you dont understand or need help on. Always interested in new projects as well 8-)
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Postby davewanna » Tue Oct 22, 2013 7:45 pm

Thanks, I'll grab that program and have a play to get my head around the protocol.

My interest in reading the bus has several causes, I play with microcontrollers as a hobby, and want to interface a PIC to read information to achieve a couple of things. One is to output the right pulse to get a correct reading on my factory 4cyl tacho. Another is to output a signal for driving a logometer that I intend to put in the speedo. That way I can easily correct my speed due to different wheel/tyre combinations I'm running.

Also I intend to use the PIC to monitor vital signs, and give an audible tone if anything goes out of range (temp, volts, etc)

My previous vehicle PIC projects have been creating a climate control system in old cars, I have done 2 where I read each sensor individually (TPS, Evaptemp, Volts, RPM, Speed, A/C pressure, etc) This did work perfectly, but this time I would like to read everything off the bus.

Cheers for the info
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Postby TazzI » Thu Nov 07, 2013 6:25 pm

davewanna wrote:Thanks, I'll grab that program and have a play to get my head around the protocol.

My interest in reading the bus has several causes, I play with microcontrollers as a hobby, and want to interface a PIC to read information to achieve a couple of things. One is to output the right pulse to get a correct reading on my factory 4cyl tacho. Another is to output a signal for driving a logometer that I intend to put in the speedo. That way I can easily correct my speed due to different wheel/tyre combinations I'm running.

Also I intend to use the PIC to monitor vital signs, and give an audible tone if anything goes out of range (temp, volts, etc)

My previous vehicle PIC projects have been creating a climate control system in old cars, I have done 2 where I read each sensor individually (TPS, Evaptemp, Volts, RPM, Speed, A/C pressure, etc) This did work perfectly, but this time I would like to read everything off the bus.

Cheers for the info

Sounds like a great project!
I imagine alot of people (myself included) would enjoy watching you progress with that if you do even intend to document your progress.
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Postby nikolatesla » Sat May 25, 2019 5:49 pm

old thread but this sounds like low pressure switch preventing the system from cutting in.

if you check the low pressure valve (the one near the pillar) there should be over 100 psi there ..if its low then you need gas ,if there is none you need gas and oil and a vacuum pump...
As long as there is some pressure then s top up with barbeque gas (not liquid)
will solve your problem...pm me if you want specifics but a set of guages is advisable . 120bucks on fleabay.
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