VW A/C Compressor

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golfdubcrazy
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Re: VW A/C Compressor

Post by golfdubcrazy »

Great plot @pete9008

the data should be very accurate as i emulated the pressure sensor and read the values of a factory climate control module via diagnostic.
its a shame i don't know what byte 3 and 4 do as i couldn't see any values on diagnostic change.

I was trying to do the same with sending the compressor data but the climate control wasnt happy with that one.

i will get round to the humidity and temp sensor next.
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EV_Builder
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Re: VW A/C Compressor

Post by EV_Builder »

its possible that the the other 2 bytes are fine value. Like 0-4bar representation. and that the other 2 bytes are course.
So to get the total pressure you calculate the 0-4bar values and the course value and sum them up.

I came across a current sensor who did this with 2 analog outputs.
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golfdubcrazy
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Re: VW A/C Compressor

Post by golfdubcrazy »

EV_Builder wrote: Mon Sep 19, 2022 10:08 pm its possible that the the other 2 bytes are fine value. Like 0-4bar representation. and that the other 2 bytes are course.
So to get the total pressure you calculate the 0-4bar values and the course value and sum them up.

I came across a current sensor who did this with 2 analog outputs.
i will give it a try tomorrow but when i applied pressure the the sensor (in a previous attemp to get some readings) i didnt see those values change
golfdubcrazy
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Re: VW A/C Compressor

Post by golfdubcrazy »

I just simulated the AC pump to the climate control and got some values. They seem very different from muehlpower results but these are from VCDS so i trust them. i didnt not go thru all the error and status options but i will in the future.


byte 1 errors
to do later

byte 2 status inverter temp
01 overheat pre warm stage
02 overheat shutdown active
03 error temo sensor
04 ok
80 inverter status active

byte 3 status
01 compressor off
20 compressor on
40 rpm limitation active
80 self protect shutdown stage 3 active
aa self protect shutdown stage 2

byte 4 rpm
01 50rpm
02 100rpm
30 2400rpm
60 4800rpm
aa 8500rpm
bb err
cc err
ee err
fe err
ff err

byte 5 compressor motor current
01 0.25a
02 0.50a
60 24.00a
aa 42.50a
bb 46.75a
ee 59.50a
fe 63.50a
ff error


byte 6 ac compressoer power con KW
01 0.04kw
02 0.08kw
60 3.84kw
aa 6.80kw
bb 7.48kw
ee 9.52kw
fe 10.16kw
ff error

byte 7 compressor temp
val temp
01 -126
02 -125
aa 43
bb 60
ee 111
fe 127
ff error

byte 8 high voltage supply
01 2v
02 4v
60 192v
aa 340v
bb 374v
ee 476v
fe 508v
ff error
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EV_Builder
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Re: VW A/C Compressor

Post by EV_Builder »

golfdubcrazy wrote: Mon Sep 19, 2022 11:26 pm They seem very different from muehlpower results but these are from VCDS so i trust them. i didnt not go thru all the error and status options but i will in the future..
This looks like CANBus, Muehlpower = LIN bus.
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golfdubcrazy
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Re: VW A/C Compressor

Post by golfdubcrazy »

EV_Builder wrote: Tue Sep 20, 2022 6:36 am This looks like CANBus, Muehlpower = LIN bus.
no this is definitely the linbus data from the compressor
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EV_Builder
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Re: VW A/C Compressor

Post by EV_Builder »

golfdubcrazy wrote: Tue Sep 20, 2022 7:55 am no this is definitely the linbus data from the compressor
Then it's time to compare nameplates on the compressor and or the device between the compressor and vcds interface.
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Pete9008
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Re: VW A/C Compressor

Post by Pete9008 »

Nice work :)

Those look pretty close to me, well within the uncertainty that's to be expected when reverse engineering something. Interesting to see that you have motor power and current while muehlpower doesn't. Is it possible that the controller is sending something to the compressor that 'wakes up' those fields? Are you able to do a capture of the data being sent to the compressor from the controller? Alternatively it could be model dependant as EV_Builder suggests.

Muehlpower's 112 value (hex 0x70) for byte 1 looks like a combination of your compressor on and rpm limitation active flags and suggests that there is another flag on 0x10.
golfdubcrazy
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Re: VW A/C Compressor

Post by golfdubcrazy »

as these are the values the control unit are giving I would say they are right. I'm assuming Muehlpower did some very accurate guess work. also just realized what's in his original post lines up with my results and theres a few mistakes in the wiki.
as i am emulating the pump and the values are clear on the screen doesn't leave any guessing
vcds.jpeg
i just done the HV heater this was my results.

byte 1 current (n*0.25)
01 0.25a
02 0.50a
30 12.00a

byte 2 high voltage status
01 hv too low
02 hv too high
04 hv ok

byte 3 status
01 ptc degraded by sw
02 malfunction
08 ok

byte 4 ?

byte 5 supply voltage (n*0.1)
01 0.1v
02 0.2v
99 15.3
fb 25.1
fe initialzation

byte 6 temp control module (n-50)
10 -34c
11 -33c
30 -2
31 -1
60 46
88 86
87 85
99 103

byte 7 inlet temp (n-50)
10 -34c
11 -33c
30 -2
31 -1
60 46c
88 86
87 85
99 103


byte 8 exh heat (n-50)
10 -34c
11 -33c
30 -2
31 -1
60 46c
88 86
87 85
99 103c
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