Aux fan not turning on

[Manny G.]

So as the title states, the electric aux fan isn't turning on.


I tested the connector with a multimeter, with the car off it still shows 12.5v .. the signal wire shows about 5mV

I changed the fan. Old fan was throwing code on DME about "8D/01 Activation, electric fan" .. changed the fan, cleared the code, never came back. fan still never turned on

I unplugged the lower radiator hose temp switch.. also shorted the pins, fan still never turned on

Being that I had 12 volts at the connector, I didn't think it would be a fuse problem.. but I checked them ALL anyway. No fuses blown.

Turning AC Max on, still no fan

Letting the car run then idle at running temperature, still no fan

Not entire sure if it's related, but the AC doesnt blow cold either.. I'm assuming at this point that its because... no fan.

Edit: this is an '01 with the 3-pin PWM fan, no external resistor. --- does this one still use relay K20/K21?



Any ideas would be greatly appreciated, thanks!

[purplecty]

Try activating it with INPA? You sure the new fan is good? No errors still?

[Manny G.]

Try activating it with INPA? You sure the new fan is good? No errors still?

Definitely no errors for the fan anymore.. its an original BMW fan, used, but was sold as working tested good. These fans never power up for me when I try to test them externally, the PWM signal restricts putting 12V and having it start

I've actually forgotten all about the INPA method to test the fan... probably because my INPA is in all German and frustrating to use. Do you have a screen capture of the INPA screen where you test the fan?

[Timm]

If the A/C compressor is not cutting-in then the auxiliary fan will not fire up unless the car starts over-heating. The auxiliary fan is primarily for the air conditioning condenser.....

[purplecty]

Definitely no errors for the fan anymore.. its an original BMW fan, used, but was sold as working tested good. These fans never power up for me when I try to test them externally, the PWM signal restricts putting 12V and having it start

I've actually forgotten all about the INPA method to test the fan... probably because my INPA is in all German and frustrating to use. Do you have a screen capture of the INPA screen where you test the fan?

Its under the dme and activate screen. I have always been able to activate a good fan with INPA. There is also a giant 50amp fuse in the DME box as well but you should still get an error if that is blown IIRC...

[Manny G.]

So the AC compressor clutch turns on when the system is turned on, and stops when its off. I checked that the compressor was engaging and disengaging the clutch when i first noticed i didnt have cold air. I still only get hot air though..

I also waited over 20 mins of idling, the car was nice and hot, the fan still didnt turn on.


I did check that 50amp fuse in the e-box.. even put a multimeter through it and it got continuity fine. Thanks for that tip, ill try with INPA later tonight or tomorrow .

[Manny G.]

So an update on this,

I disassembled the fan, cleaned and dusted all of the circuit boards. They are all epoxy coated so there isnt any corrosion that i was able to see. I have NOT been able to get any fan to turn on at all using INPA.


I did however connect to my IHKA with INPA, noticed a signal labelled "DME - KO Signal" fluctuating to AUS and EIN very frequently. Ive also noticed a few occasions where pushing the MAX button doesnt work or turn on.

I still cant get cold AC blowing. .. thinking bad IHKA module?

[purplecty]

So an update on this,

I disassembled the fan, cleaned and dusted all of the circuit boards. They are all epoxy coated so there isnt any corrosion that i was able to see. I have NOT been able to get any fan to turn on at all using INPA.


I did however connect to my IHKA with INPA, noticed a signal labelled "DME - KO Signal" fluctuating to AUS and EIN very frequently. Ive also noticed a few occasions where pushing the MAX button doesnt work or turn on.

I still cant get cold AC blowing. .. thinking bad IHKA module?

Could be! They can be had pretty cheap just make sure you program it to the car. Does the IHKA have any errors? Does the snowflake activate the AC compressor? I believe you said it was so that may rule out the IHKA. Did the DME error for fan activation ever return?

[Manny G.]

Could be! They can be had pretty cheap just make sure you program it to the car. Does the IHKA have any errors? Does the snowflake activate the AC compressor? I believe you said it was so that may rule out the IHKA. Did the DME error for fan activation ever return?

The snowflake button does activate the AC compressor, yes.. but the MAX button has been intermittently working.

What is "DME - KO Signal"? Is that the signal from the DME to the compressor? KO IIRC usually meant for "Kompressor"

[racer2086]

Is the fan new or used?

The DME KO fluctuates on my car also. Don't worry about that.

It's possible the IHKA has issues. However, do you have a good charge of R134a in the system? Have you worked on it recently? Aux fan or not, you should notice even some cooling of the air when you first turn the A/C on as the condenser isn't wicked hot.

Because you have a PWM fan, you cannot test the fan other than using INPA. That fan does not use relays and the power is constant 12v to it. Getting voltage to it is only part of the puzzle, as it needs the PWM signal in order to activate and know the speed. That being said, my INPA throws an error when I try to activate the fan (I do have a pre-facelift car, but that shouldn't matter). So I can't rely on my INPA to test it, and maybe you have a similar INPA problem.

[Manny G.]

Is the fan new or used?

The DME KO fluctuates on my car also. Don't worry about that.

It's possible the IHKA has issues. However, do you have a good charge of R134a in the system? Have you worked on it recently? Aux fan or not, you should notice even some cooling of the air when you first turn the A/C on as the condenser isn't wicked hot.

Because you have a PWM fan, you cannot test the fan other than using INPA. That fan does not use relays and the power is constant 12v to it. Getting voltage to it is only part of the puzzle, as it needs the PWM signal in order to activate and know the speed. That being said, my INPA throws an error when I try to activate the fan (I do have a pre-facelift car, but that shouldn't matter). So I can't rely on my INPA to test it, and maybe you have a similar INPA problem.

Thanks for that... I thought the fluctuating was a sign of the IHKA having issues.

I'm not entirely sure of the R134a charge,... I did pressure test the low side and pressure was fine. I don't have anything to test the high side. The fan is used "in working condition" as it was sold to me. I've tried INPA on the fan and nothing happens. Just for sanity, I tested it on my E39, and the fan started up after a few seconds when testing it through INPA. When I try the test on the E38, I get no error or anything other than the small grey screen that says the fan was activated in German.

[Manny G.]

Also, found this in the TIS


https://www.newtis.info/tisv2/a/en/e...rfaces/XhQ7o0I
Compressor activation
Communication between engine electronics - heating/air conditioning system
Communication via K-bus

As from model year 1999, a telegram will be used on the K-bus in order to transfer signals to the DME/DDE. The ready and request signal is transmitted bit-coded in the telegram and the compressor capacity in Nm .

Feedback from the engine electronics takes place via a separate line (DME-KOREL).


https://www.newtis.info/tisv2/a/en/e...ioning/XZeepw0
Air conditioning control
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 fulfilled. 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 .

Switching conditions for the electromagnetic clutch
ON (all conditions must be fulfilled)-------------------OFF (one of the conditions must be fulfilled)--------------------------Remarks
Air conditioning button ON---------------------------Air conditioning button OFF
Air flow control wheeldriver out of zero position-------Air flow control wheeldriver in zero position
Evaporator temperature > 3 o C----------------------Evaporator temperature < 2 o C ------------------------------------Dependent on outside temperature: The cut-out threshold drops by 1 °C at temperatures above 20 °C
Enable sent from DME (DME-KOREL)------------------Full throttle signal from DME initiates shut-down with respect to time--Cut-out temporally limited to approx. 3 seconds.
Engine speed >600 rpm------------------------------Speed dropped below minimum value (600 rpm)

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.



There's more but its too difficult to post here some of the charts shown on the TIS. This shows a breakdown of the nM applied with the pulse signal: https://www.newtis.info/tisv2/a/en/e...ry-fan/XMBUEDL

[purplecty]

INPA always activates good fans for me...

[racer2086]

So Manny that's great you were able to test on the E39. Tells you both the fan and INPA work. Something is going on with your car.

In regards to the system pressure, you can't tell the fill/charge my measuring the pressure. To charge properly, you have to evacuate and recharge with the correct measured amount.

For the fan, you know you have power with the 12v you measured. Have you verified ground? Use your multimeter to check continuity between the ground pin in the harness and a good ground point on the chassis. That should be basically continuous. If that is good, next would be troubleshooting the IHKA (has it been replaced and needs recoding?) And then the DME.

Probably the first thing I should have asked is: has the fan worked for you before and has the A/C worked before? Is this a new car to you or do you have history on what's been done e.g. IHKA replaced.

[rslifkin]

In regards to the system pressure, you can't tell the fill/charge my measuring the pressure. To charge properly, you have to evacuate and recharge with the correct measured amount.

You'll never get it dead on by pressure, but it's quite possible to get it close enough with a combo of pressure gauges and a vent temp thermometer. E38s use an expansion valve system, so they're not nearly as sensitive to charge volume as a simpler orifice tube system. As long as the charge is correct-ish, the system will work fine. Too much charge will lead to excessive high side pressure, too low will cause poor cooling performance.

[racer2086]

You'll never get it dead on by pressure, but it's quite possible to get it close enough with a combo of pressure gauges and a vent temp thermometer. E38s use an expansion valve system, so they're not nearly as sensitive to charge volume as a simpler orifice tube system. As long as the charge is correct-ish, the system will work fine. Too much charge will lead to excessive high side pressure, too low will cause poor cooling performance.

I agree with the sentiment that the system will get by if the fill isn't perfect. But my experience is that it's hard to get close to the correct fill, especially based on your ambient temperature and with the PWM compressor and aux fan and all of this computer controlled stuff. It will do its best to compensate for the incorrect charge, i.e. the aux fan will run a lot with a high charge or the PWM compressor will run at full bore with a lower charge. You can literally hook up manifold gauges and add can after can. As you get more oz in the system, the high side will run up in pressure, but the car will sense this and flip on the aux fan or pull off the compressor, pulling the high side down to level out the pressures. So it's a guessing game.

[Manny G.]

The car was new to me, 1 owner. The AC didnt blow cold when I bought the car. Seller said it did seem to blow cold recently... but then again, he is originally Canadian,.. sooo cold is a matter of perspective to him.


It came with an off brand aftermarket fan, I changed the aftermarket brand fan for an original used BMW one assumed in working condition. I've checked each and every fuse, all seem fine. It could be simply that the car needs a full flush of the AC system and perhaps moisture in the system,... maybe a new dryer too?

Tomorrow I'm going to put the E39 and E38 face to face and connect the fan from the E39 to the E38s harness and see if it fires up... the E38 one thankfully has enough slack to reach and the E39 is right up front behind the kidney grille


I'll reply back with results soon

[Manny G.]

Ok, so update.... the fan on the E38 is GOOD, confirmed working. I connected the E38 fan to my E39, hit MAX AC, within a few seconds, it twitched, and fired right up. From the other end, I hooked up the E39 fan to the E38, hit MAX AC, nothing. Something is definitely up with the E38's system

Some shots of something you dont see every day.. the perks of owning more than one M62tu

IMG_20191206_115618.jpg

Hows this for cutting it close..
IMG_20191206_115339.jpg

IMG_20191206_115502.jpg

[purplecty]

Have you checked the large 50amp fuse in the ebox of the e38?

[Manny G.]

Have you checked the large 50amp fuse in the ebox of the e38?

Yes, the 50amp fuse 78 I believe its numbered, large fuse in the e-box off to the side... I've pulled it out so many times, scrapped the connectors with a wire brush to make sure it was making good contact, even tested it with a multi-meter... the fuse is good.

[purplecty]

Yes, the 50amp fuse 78 I believe its numbered, large fuse in the e-box off to the side... I've pulled it out so many times, scrapped the connectors with a wire brush to make sure it was making good contact, even tested it with a multi-meter... the fuse is good.

Have you physically checked the DME for any corrosion and all of the wiring for the fan on the e38? 2 of my favorite cars in the picture! That alpine white e38 looks sweet!

[Manny G.]

Have you physically checked the DME for any corrosion?

Yes, I pulled out both the EGS and the DME... found small traces of water residue/corrosion on the EGS only, nothing on the DME. Opened the EGS, it was fine. The corner of the EGS that had some water was mainly on a communication bus pin.

[purplecty]

Did you also try activating the e38 fan with INPA hooked up to the e39?

[Manny G.]

Did you also try activating the e38 fan with INPA hooked up to the e39?

No, didn't even bother hooking up the laptop to try. Once I saw that the fan on the E38 started up, it was enough to rule out bad fan which was my main concern. I'm fairly confident that if I tried to use INPA through the E38 to turn on the E39's fan, it would still not run.

I've narrowed it down to the systems R134a charge, bad IHKA or both. I may have to bite the bullet and take it to an AC specialist, I was hoping to avoid that since at some point this AC system wont even be in the car... but until then I still live in Florida and I'd still like to enjoy the car before I start on the swap.

[racer2086]

You've done fantastic diagnostic work. And you have narrowed this right down.

The only two things you haven't tested...
Did you check the ground wire at the aux fan connector for continuity to ground?
Did you check the continuity of the PWM wire from the aux fan connector to the DME connector?

The other thing we don't know is if the car will disable the aux fan if the r134a pressure is low. However, the compressor turns on, so I can't imagine it is low enough for that fan not to run. But then again, that may be based on the high-side pressure, which could be low due to a low charge. I wouldn't bet on it.

Once you check that the two other wires in the connector are good, I'd get another IHKA and code it to the car and try it out. You should be able to get one easy from the LKQ on 441.