IHKA no communication, aux fan always on

[toma3757]

Hi!
This is my first post here, so please be tolerant.
I bought my first E38 740i '95 last month. Today I've finished my "almost free ads interface" which communicates with some modules (for example DME, LCM, PDC) but it can't communicate with IHKA. I get this error:

Error#19 IFH-0009: NO RESPONSE FROM CONTROLUNIT Api job error or no such result!

I've found an unplugged connector behind the IHKA module: 1-963 615-1 BMW 8365900
The module has not got an empty socket so I can't plug it in.
I think everything works fine with the module,it can control the temperature, blowing speed..etc.

This diagnosis is needed because the aux fan always works when I turn on the ignition (it turns on when the ac is off too)
I checked the fuses and the relays, both are fine. I will continue maybe with the resistor inside the fan's box.

Can somebody help me please? Are these errors linked?
What is this connector?
Thanks!

[Elver]

I dont know very much but have you made sure someone did not jump the aux fan harness?
Aux fan harness is off the radiator next to the overflow tank.
Does it spin fast or slow speed? Is it always the same speed?

[toma3757]

Thanks for your answer.
I don't think somebody messed up the harness.
I figured out, if I unplug the B8 - high pressure switch (https://www.newtis.info/tisv2/a/en/e...peed-2/nEBOCtY)
The fan doesn't start automatically when I turn on ignition and AC is off.
That means my pressure is below 17.5 bar maybe, but how much should it be? between 17.5 and 20 bar?

It would be easier to find out if I can open this controller in INPA, but I don't know why is this error.

It is always the same speed, and it spin fast, stage2 relay turn the fan on.

[chemmech]

a reference to B8 pressure switch operation .

"The triple pressure switch opens the power circuit to the electromagnetic clutch when the refrigerant pressure drops below the value set for low pressure or exceeds the value set for high pressure.

Low pressure Medium pressure High pressure
ON< 2.8 +/- 0.2 bar ON> 20.0 +/- 1 bar ON> 33.0 +/- 1 bar
OFF>1.9 +/- 0.2 bar OFF< 17.5 +/- 1 bar OFF< 23.5 +/- 1 bar" https://www.newtis.info/tisv2/a/en/e...ry-fan/XMBUEDL

...might be a faulty switch you need to check it with a multimeter carefully since the a.c. system has to get opened up if it is bad.

- - - Updated - - -

B8 contacts 5 and 6, do they make up the medium part of the B8 triple switch?

- - - Updated - - -

seems like it's shorted but it needs to get checked out.....

[chemmech]

I don't thinks it's possible but is the system overfilled too much refrigerant? maybe the car heats up trips the switch have no idea I'd also check the system pressure with some gauge before buying an $90 switch......

[chemmech]

the switch is under pressure so the system refrigerant needs to be recovered etc. before removing the switch, taking a bath in freon is no fun frostbite.... a disclaimer....

[toma3757]

a reference to B8 pressure switch operation .

"The triple pressure switch opens the power circuit to the electromagnetic clutch when the refrigerant pressure drops below the value set for low pressure or exceeds the value set for high pressure.

Low pressure Medium pressure High pressure
ON< 2.8 +/- 0.2 bar ON> 20.0 +/- 1 bar ON> 33.0 +/- 1 bar
OFF>1.9 +/- 0.2 bar OFF< 17.5 +/- 1 bar OFF< 23.5 +/- 1 bar" https://www.newtis.info/tisv2/a/en/e...ry-fan/XMBUEDL

...might be a faulty switch you need to check it with a multimeter carefully since the a.c. system has to get opened up if it is bad.

- - - Updated - - -

B8 contacts 5 and 6, do they make up the medium part of the B8 triple switch?

- - - Updated - - -

seems like it's shorted but it needs to get checked out.....

Thanks!
I will check these pins tomorrow.
I don't think It's overfilled because when the pressure was 5bar (before the filling), the fan was always on too. If i remember well, after the filling the pressure was about 10bar. I think it is ok, doesn't it?

[toma3757]

Sorry for the late answer, I had a lot of other things to do
I measured the pressure switch, but it was not "short circuit" between pin 2 and 3 (https://www.newtis.info/tisv2/a/en/e38-740i-lim/YcV0Sio https://www.newtis.info/tisv2/a/en/e38-740i-lim/k2YVjVJ)
At the connector side, checked for continuity it was not shortened but the mutlimeter showed values which looked like a diode's value, maybe i measured the output transitor.
Talked with my friend who told me, if the pressure is too high, it doesn't even turn on but if the pressure is low it could cause this problem.
My climate is cold so I don't think the pressure is low.
I don't know that to do next..It would be easier if the pressure switch was shortened but it isn't.
Inpa still can't communicate to the IHKA. can you suggest something?
Thanks!

[chemmech]

since the switch checked out good, seems like a control system problem, are you sure you don't have another connector maybe got shoved far back out of view for the ihka? or possibly try to track down the proper ihka module?

[toma3757]

since the switch checked out good, seems like a control system problem, are you sure you don't have another connector maybe got shoved far back out of view for the ihka? or possibly try to track down the proper ihka module?

If i'm right, the IHKA can't turn on the stage2 on the fan. Because here: https://www.newtis.info/tisv2/a/en/e38-740i-lim/lN4zjRl the stage 2's relay coil is fully separated from the IHKA, right?
So maybe I got a wiring problem, somewhere it is grounded.

I have this ihka module: 64116901307, everything is connected to it, but i have an unplugged connector on that area, but i don't know how to figure out where it should go.
Unplugged connector behind the IHKA module: 1-963 615-1 BMW 8365900 that's all I know from this.

[chemmech]

yeah it seems the ihka isn't in the aux fan stage 2 wiring in the schematic you showed https://www.newtis.info/tisv2/a/en/e38-740i-lim/lN4zjRl

check b8 pressure switch contacts for proper operation between pins 5 and 6; with the a.c. off there should be no continuity or o.l. on the multimeter and when the a.c. is running there should be continuity or very close to zero ohms on the multimeter according to the schematic

the pressure switch b8 may have gotten too sensitive so it may be a bad switch..... try unplugging the radiator temp switch when doing the test to isolate the problem to the a.c. system then plug it back in when done....

[Timm]

The 1995 was the only E38 model that got an old-fashioned circuit diagram which should make fault finding a lot easier! Here's the relevant page:

https://www.meeknet.co.uk/E38/BMW_95...ram.pdf#page=4

[toma3757]

Thanks for the info.
Measured again the B8 high temperature switch, I was lame at first, now between pin 2 and 3 it is shorted.
This means the pressure is below 17.5 bar. Is it normal? How much should it be at ignition, before first start, about 20°C?
It should be above 20 bar? Maybe the refill was not enough?

[Timm]

You are getting confused! There are two switches for the aux fan: A pressure switch that measures refrigerant pressure, and a temperature sensor that measures the outlet temperature from the radiator.

With the A/C OFF the pressure switch is ignored
The temperature​ switch does nothing until the temperature reaches 91C - the aux fan then runs at normal speed - when the temperature reaches 99C the aux fan runs at high speed.

[toma3757]

You are getting confused! There are two switches for the aux fan: A pressure switch that measures refrigerant pressure, and a temperature sensor that measures the outlet temperature from the radiator.

With the A/C OFF the pressure switch is ignored
The temperature​ switch does nothing until the temperature reaches 91C - the aux fan then runs at normal speed - when the temperature reaches 99C the aux fan runs at high speed.

Yes I'm confused. The first part is ok, but i don't understand the second. Why it is ignored? The fan goes on high speed after I turn igniton on when AC is off so it should be ignored. After I unplug the pressure switch's connector, the fan stops.
At the schematic nothing proves that it is ignored. That's a completely independent circuit, doesn't it?

I think the high speed stage should work like this: If the temperature above 99°C OR the pressure switch turned on(pressure below 17.5bar) according to the schematic.

Maybe you are right, but I don't have enough information about it. Which part is the problem in my case?

Thanks!

[chemmech]

it seems there might be a wiring issue have you check the relays that run the fan system under the glove box for any thing that looks out of place? the only thing run by the a.c. switch should be stage 2 speed and stage 1 speed on some models.....

- - - Updated - - -

if you have auxiliary fan with the resistor pack someone may have jumped to the higher stage if one of the lower speed reisistrs went bad.....

[chemmech]

correction "resistors"

[toma3757]

it seems there might be a wiring issue have you check the relays that run the fan system under the glove box for any thing that looks out of place? the only thing run by the a.c. switch should be stage 2 speed and stage 1 speed on some models.....

- - - Updated - - -

if you have auxiliary fan with the resistor pack someone may have jumped to the higher stage if one of the lower speed reisistrs went bad.....

Yes, I checked the relay. It's good. ( https://www.newtis.info/tisv2/a/en/e38-740i-lim/V8iDgPT )
The pin 4 is "low" (grounded) so it turns the fan on, (https://www.newtis.info/tisv2/a/en/e38-740i-lim/ZFh1KWR)
After I remove the stage 2 relay it shuts down, so it is not jumped I think.
After I unplug the high pressure switch's connector, the fan stops so the double temperature switch is good (and the relay).
I don't know, the pressure switch is broken or the pressure is "bad". I think I should visit an A/C specialist, I don't have enough infromation for this.
How musch should be the preassure at the "pressure switch"?

[toma3757]

Found the missing information.
"
When refrigerant high-side pressure exceeds 290 psi (20 bar), the pressure switch
contacts close, energizing the high speed relay. The fan runs at high speed."
From the "e38 ihka manual". Maybe it means the TIS's info is false.
This means i have to replace the high pressure switch.
Thanks for the help!

[chemmech]

that's good to know, pressure varies a lot but definitely shouldn't be stuck on high pressure either to much freon or bad switch or other issue causing high pressure ....

[johnroyjr]

If i'm right, the IHKA can't turn on the stage2 on the fan. Because here: https://www.newtis.info/tisv2/a/en/e38-740i-lim/lN4zjRl the stage 2's relay coil is fully separated from the IHKA, right?
So maybe I got a wiring problem, somewhere it is grounded.

I have this ihka module: 64116901307, everything is connected to it, but i have an unplugged connector on that area, but i don't know how to figure out where it should go.
Unplugged connector behind the IHKA module: 1-963 615-1 BMW 8365900 that's all I know from this.

Did you ever figure out what the 1-963 615-1 BMW 8365900 plug goes to?

[toma3757]

Did you ever figure out what the 1-963 615-1 BMW 8365900 plug goes to?

Sorry for the late answer.
Unfortunately not found where it goes.
Do you have the same plug unconnected?

[SergeBMW]

If you haven't already, you need to unplug the aux fan switch that is on the passenger side of the radiator. This is what controls your fan speed with A/C off. Unplug it and turn the key to ON. It should no longer run the aux fan with this cable disconnected.

[toma3757]

If you haven't already, you need to unplug the aux fan switch that is on the passenger side of the radiator. This is what controls your fan speed with A/C off. Unplug it and turn the key to ON. It should no longer run the aux fan with this cable disconnected.

My problem was solved by replacing the high pressure switch.
The unconnected plug is in the center console behind the AC control panel.