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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 05-11-2013, 04:10 PM
xsailor xsailor is offline
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Mein Auto: 01 E39 525it, 93 M5 Euro
Strange AC problem

AC was working fine yesterday no go today .E39 525 with dual zone climate control. I scanned the AC with INPA all of the sensors seem fine . I attached pressure gauge to the low side and started DIS scanned AC no faults so I went into the test menu forced the compressor to start, it worked cold air came out of the vent but the pusher fan did not start. All of the fuses are good including the 2 behind the glove compartment.
The low side pressure looked high but fell into the operating range when I started the compressor with DIS. Would high head pressure on the low side cause the compressor not to start? If so why would it have worked yesterday.
Can anyone tell me where to look next?



Thanks in advance. XS
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Last edited by xsailor; 05-11-2013 at 04:13 PM.
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  #2  
Old 05-11-2013, 05:59 PM
rdl rdl is online now
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What year is the 525? Some the details of operation vary by year.

What was ambient temp, and ambient reading in instument cluster?
I notice eastern Canadian temps are around 10C. On at lesst some years, A/C cooling is disabled at ambient 10C or lower. Even at say 15C ambient, cooling may not be called by IHKA unless target temp is set quite low.

Do you have PWM aux fan or earlier 3 stage? Did you check high side pressure with compressor running?
On models with PWM aux fan, the fan is not started until high side pressure reaches 10 bar, which it might not do for some time in cool ambient temps. I believe 3 stage fan turns on with A/C compressor, & will verify this in WDS for you if that is what you have.
IIRC, INPA in DME module can force fan operation, at least in PWM version. You might try that to set your mind at ease (or not ) regards aux fan function.

Higher than normal operating pressure on low side with compressor stopped is normal. When compressor is not running, pressure equalizes throught the entire system, i.e. no difference high side to low side. R134a expected pressure from thermodynamic tables at 10C is ~45 psi.

The fact that low side pressure fell when the compressor was forced on is good news; the compressor is at least compressing. And of course you got colder air when compressor forced to on.
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Last edited by rdl; 05-11-2013 at 06:16 PM. Reason: Typo - misplaced by ???
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  #3  
Old 05-11-2013, 07:15 PM
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16valex 16valex is offline
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Quote:
Originally Posted by xsailor View Post
AC was working fine yesterday no go today .E39 525 with dual zone climate control. I scanned the AC with INPA all of the sensors seem fine . I attached pressure gauge to the low side and started DIS scanned AC no faults so I went into the test menu forced the compressor to start, it worked cold air came out of the vent but the pusher fan did not start. All of the fuses are good including the 2 behind the glove compartment.
The low side pressure looked high but fell into the operating range when I started the compressor with DIS. Would high head pressure on the low side cause the compressor not to start? If so why would it have worked yesterday.
Can anyone tell me where to look next?



Thanks in advance. XS
Check the plug to the aux fan for corrosion and make sure all fuses are OK.

If all is OK then your aux fan is dead. M54 engine the A/C needs to have a good working aux fan in order to run.
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Old 05-11-2013, 07:25 PM
xsailor xsailor is offline
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Thanks for the reply I forgot to add a few of the things you pointed out the car build date is 2001-09 so the pusher fan is the new style (no resister pak) and was replaced last summer, the ambient temp at the time of test was 18c, interior temp was 26c and the climate control was set to 16.5c both sides. it seems my system is charged and the compressor works . All of the controls seem to function properly.
The compressor circuit must be ok or DIS would not be able to start it. No faults show up in DIS or INPA . I am stumped . If the pressure switch was bad or a circuit was open wouldn't it show as a fault. I will check the aux fan connections tomorrow I sort of ruled it out because it is only about 6 months old but you never know.
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  #5  
Old 05-11-2013, 07:33 PM
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16valex 16valex is offline
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If DIS can turn your A/C on then your Pressure switch is OK. But you can check the voltage reading at the compressor.
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  #6  
Old 05-12-2013, 04:20 AM
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diggyd357 diggyd357 is offline
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Re: Strange AC problem

Maybe the pressure switch is just "starting to go".... I know mine is, so I have to rev the engine in order to make the compressor kick on. Humor me... Next time you are in the car, turn on your ac, give it some" good gas pedal" and accelerate about 15mph and see if the compressor kix on. This is exactly how mine acted... One day it worked fine and the next day I had to "goose" the gas to make it kick on. Once it kicks on it'll stay on. Good luck, hope it works for you!!!

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Old 05-12-2013, 07:08 AM
rdl rdl is online now
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The best suggestion I have is to use INPA or DIS to check all condtions and values as listed for compressor clutch operation below. It's possible that a sensor signal is getting mangled &/or the IHKA panel has a fault, engine RPM value, etc.

Regards auxillary fan operation, WDS is quite clear that A/C function does not turn on the PWM auxillary fan until A/C pressure reaches 10 bar. I have observed delayed aux fan start with my A/C in a 2003 530. So your fan not running immediately when A/C is switched on is not necessarily indication of a fault in the fan. Since you have DIS and INPA, you could run the fan test sequence to confirm operation. I'm pretty sure the test function is found in the DME section rather than IHKA.

I must apolgize for mistaken information in an earlier post: specifically the 10C minimum ambient for compressor operation. Rather idle speed boost requires a minimum ambient and that is -ve 10C not +ve 10C. See the WDS quotes below.

As an aside, it's a mystery to me why the compressor would ever be required with a -10C ambient; maybe if in recirc mode with a warm cabin and A/C needed for dehumidification? Which seems an unlikely set of circumstances.

There are 2 descriptions of A/C control in WDS
**************
Evaporator control (compressor control)

Evaporator control is activated by pressing the A/C button in the operating unit. A/C standby mode is indicated by the LED in the A/C button. If controlled compressors are installed, the cutout threshold is dependent on the outside temperature and may be between 1C and 3C. If a standard compressor is installed, the threshold is reduced by 1C at high outside temperatures (> 30C). The compressor and auxiliary fan are controlled directly by the digital engine or diesel electronics (DME/DDE). Requests for A/C compressor and auxiliary fan are sent via the K-bus to the DME/DDE. The pressure sensor also monitors the refrigerant pressure and switches the A/C compressor off if the pressure is too high or too low.

Switching conditions for the magnetic clutch:

ON:A/C button ON and evaporator temperature > 4C (depending on the outside temperature) and coolant temperature < 117C and terminal 30 at control module > 9.7 Volt.

OFF: A/C button OFF or evaporator temperature < 3C (depending on outside temperature) or blower stage 0 or coolant temperature > 120C or terminal 15 OFF or terminal 30 < 9 Volt.

Switching conditions for DME AC idle boost:

When the A/C button is pressed, the heating/air conditioning system requests an idle speed boost via the K-bus in order to provide adequate cooling capacity at idle speed.

ON: A/C button ON and outside temperature > -10C.

OFF: A/C button and DME_KO OFF or blower 0 and DME_KO OFF or outside temperature < -10C and DME_KO OFF

DME_KO compressor activation:

The DME/DDE receives the instruction to switch on the compressor via the K-bus. Provided full load cutout is not active, the DME switches on the compressor via a relay. The load moment of the A/C compressor is derived from the pressure sensor signal and passed on to the DME/DDE via the K-bus.

Infinitely variable auxiliary fan control:

The refrigerant pressure in the air conditioning is registered by means of a pressure sensor and converted by means of a table into an auxiliary fan stage which is then sent to the DME/DDE via the K-bus/CAN bus. From this, the electronic engine control system then generates the control voltage for the infinitely variable fan motor .

Important!!!

New function of the IHKR46 and IHKA46 as from SW: V005.0 :

Vehicles concerned: E46 as from production break PU99 and parts from parts sales. The new software is backwards compatible. The control modules must be coded.

A protection function for the compressor has been integrated in the control module. The A/C LED flashes during initial operation and new coding of the control modules. Now operate the air conditioning system for 90 seconds at idle speed. The refrigerant and refrigerator oil are mixed and distributed during this 90 second period. The A/C LED then lights permanently. This procedure avoids an excessively high start-up torque and damage to the compressor.
**************

The second section titled "Air conditioning"

**************
Air conditioning
The air conditioning system is switched on by pressing the air conditioning button. The function LED lighting indicates that the air conditioning system is in standby mode .

The compressor only cuts in if the switch-on conditions are fulfillled. The evaporator then produces cold air which is raised to the required temperature in reheat mode with the aid of the heat exchanger.

If a mechanically controlled compressor is installed, the evaporator cut-out temperature will be dependent on the outside temperature . The cut-out temperature drops by 1 degree Celsius if the outside temperature increases above 20 C.

To protect the evaporator from icing up , the outlet temperature is monitored by means of a sensor (evaporator sensor ) and the compressor is controlled by means of an electromagnetic clutch .



Pressure sensor
Based on the coolant pressure , the pressure sensor determines the start-up torque of the A/C compressor and the necessary auxiliary fan stage and passes on this information in the form of a telegram on the K-bus to the DME/DDE .

Full load cutout
In order to shorten the rev-up time of the engine from idle up to full load , the electromagnetic clutch is switched off for a limited period of time at full throttle. The cut-out time is 3 seconds.
**************
And a schematic of the A/C sensors and compressor clutch circuit.

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  #8  
Old 05-12-2013, 07:33 AM
rdl rdl is online now
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I stumbled across a clarification on page 17 of the attached PDF.

Note the statement that the compressor clutch is controlled by a "final stage control" but it's unclear to me exactly what this means. Perhaps that clutch control has moved to the IHKA rather than a relay controlled by the DME as suggested in the WDS descriptions in my post above. Note the schematic in post above indicated clutch control by IHKA.

Although "final stage control" sounds suspiciously like the infamous FSU, I checked WDS schematics for the FSU - there is no circuit to the compressor clutch.
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  #9  
Old 05-12-2013, 11:57 AM
xsailor xsailor is offline
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Up Date

It seems my problems have gotten worse I went to the car today and attached my ADS/OBD cable to the OBD2 plug and didn't get any power LED. fist thought was bad cable so I plugged in a peake code reader it to was dead. I popped out the obd plug and tried a fluke meter no voltage at red wire B+ , I checked all of the fuses they look fine and everything seems to work except for the AC (of course) can anyone tell me where the B+ connection on the obd2 plug is fused or where it originates?
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Old 05-12-2013, 02:02 PM
rdl rdl is online now
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Schematic for OBD connector



EDIT - the following few sentences re-worded to clarify ambiguities due to a badly run on sentence.
Connector/splice X183 on pin 8 connects to modules not mandated by OBD standards. The IHKA, the HVAC panel is one of those modules.

A quote from WDS describing the diagnsotic bus communication to those other, non-OBD, modules.
**************
Functional description of bus systems
The bus system is a group signal line system on which the exchange of data or messages takes place. A bus makes it possible to connect a central module (master) with a large number of independent control units. All units are connected in parallel to the bus line.

The diagnosis bus(D-bus, TXD link) transmits data between the DIS and a control unit. The control unit to be subject to diagnosis is selected by sending a diagnosis telegram to the control unit address. In this way, on request of the tester, the control unit can convey status information and the contents of the fault code memory or activate a control unit output.

The data flow of the indicator instruments and audio system mainly takes place via the instrumentation bus (I-bus) . For instance, the data for the check control module, on-board computer, IKE display, multi-information display, navigation, radio and the telephone are transmitted on this bus.

The body bus (K-bus) is responsible for the data exchange of telegrams that are required throughout the system. For instance, the ZKE and the IHK are connected to the K-bus. The K-bus is technically identical to the I-bus.

The general module is the central module of the peripherals bus (P-bus) . Peripheral modules interconnected by means of the P-bus are installed in locations where the scope of wiring is particularly extensive, e.g. doors. The functions of the ZKE (power windows, central locking, etc.) are controlled via the P-bus. The data are sent from the ZKE via the P-bus to the corresponding peripheral module from which the individual components are activated.

The IHK stepper motors are controlled via the motor bus (M-bus) . The IHK sends telegrams that activate the stepper motor with the corresponding address.

Addressing conditions of control units

In principle, all control units in the vehicle can be addressed via the diagnosis function when the ignition is switched on.

The busses are capable of exchanging information among each other via the IKE control unit (instrument cluster electronics) . It contains the electronic control for the entire signal conditioning function and calculating the data from the instrument cluster and on-board computer. The IKE is the bus master for the I-bus/K-bus. It serves as a gateway for the D-bus that converts the telegram format of the I/K-bus to the format of the D-bus. It transmits and receives data from all modules and control units connected to the IKE via the bus systems. If, for example, the independent park ventilation function is activated at the MID, this telegram must be routed via the I-bus, IKE and K-bus to the IHK that then carries out the corresponding function. In this case, only data are allowed to pass through that, according to the address, are designated for the other bus.
**************
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Last edited by rdl; 05-12-2013 at 02:10 PM.
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  #11  
Old 05-12-2013, 02:37 PM
xsailor xsailor is offline
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pin 16

I checked fuse 14 and 15 with an ohm meter both were good, I replaced them anyway but still have 0 volts at pin 16. I than ran a jumper wire (12v) to pin 16 and connected a peake code reader turned on the ignition and it worked . I got a code that indicated AC compressor relay problem . I still cannot figure why there is no power at pin 16 but at least I have communication with the bus . I will connect the laptop and run DIS and INPA tomorrow .

XS
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Old 05-12-2013, 03:16 PM
rdl rdl is online now
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Quote:
Originally Posted by xsailor View Post
I checked fuse 14 and 15 with an ohm meter both were good, I replaced them anyway but still have 0 volts at pin 16. I than ran a jumper wire (12v) to pin 16 and connected a peake code reader turned on the ignition and it worked . I got a code that indicated AC compressor relay problem . I still cannot figure why there is no power at pin 16 but at least I have communication with the bus . I will connect the laptop and run DIS and INPA tomorrow .

XS
The schematic shows pin 16 supplied by fuse 25, pin 1 by fuse 15. Did you check 25, or did the typo gremlin stike again?
On the bright side, you're talking to the bus again.

The DTC for "compressor relay problem" is a bit of a puzzle. The schematic for your car doesn't show a relay; unless perhaps it's buried in the IHKA(?).

BTW, I see that your "mein auto" info now lists an '01 525. In an earlier post you mentioned a build date of 9/01. This should make your car a 2002 model year. The difference doesn't affect any of the WDS schematics, I'm just curious. Do you have an '01 or an '02?
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Old 05-12-2013, 04:08 PM
xsailor xsailor is offline
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relay

thanks once again, the fuse info I found showed 14 & 15 thanks for pointing out fuse 25 it was the problem I pushed it in and presto power on pin 16.
The relay code was from a peake reader so we can take that for what it is worth. It is hard to fathom how the relay could be faulty and I was able to force a compressor start with DIS. I did find a diagram that showed a compressor relay in the plastic box under the passenger side cabin filter but it could be for a pre 2000 car
http://http://www.bimmerfest.com/for...te=1&p=7579832
Tomorrow I will run INPA and try to force a fan start .
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Old 05-13-2013, 10:28 AM
xsailor xsailor is offline
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Update problem solved

Thanks to everyone that helped me with this .
The problem was a bad connection on the main plug for the Aux. fan
I found out by running DIS 57 and trying to force the fan the dis has TIS built in and I was able to trouble shoot using the directions .
I also found out that there is an AC compressor relay on the 99 and up cars it is in back of the glove box.
The AC will not start unless the aux fan circuit is complete the fan does not necessary have to start (depends on temp) but the circuit must work.
Once again a special thanks for the outstanding assistance.

XS
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Old 05-13-2013, 10:40 AM
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16valex 16valex is offline
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Thanks for the report back.
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  #16  
Old 05-14-2013, 07:48 AM
rdl rdl is online now
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Quote:
Originally Posted by xsailor View Post
Thanks to everyone that helped me with this .
The problem was a bad connection on the main plug for the Aux. fan
I found out by running DIS 57 and trying to force the fan the dis has TIS built in and I was able to trouble shoot using the directions .
I also found out that there is an AC compressor relay on the 99 and up cars it is in back of the glove box.
The AC will not start unless the aux fan circuit is complete the fan does not necessary have to start (depends on temp) but the circuit must work.
Once again a special thanks for the outstanding assistance.

XS
Thanks for the useful addition to the details of A/C operation.

I'm surprised & disappointed at a compressor relay on the '99 up cars. I've always assumed WDS was accurate and definitive regards any and all of the electrical systems. And WDS schematics for later cars show the compressor clutch controlled directly by the IHKA and further does not even list an A/C compressor relay in the components section. Even the earlier cars show the clutch controlled by the HVAC panel through a 2 stage R134a pressure switch - no relay. The earlier cars do show one of the relays for the 3 stage fan system behind the glovebox - but this is not the same thing at all.

Was this new info was in DIS V57? Do you happen to recall the menu path to get to it? When I hunt through the V57 document menu I find a schematic the same as WDS.
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