Aux fan not turning on

[purplecty]

I just feel that INPA should activate the fan regardless of the pressures in the car. That just sends direct power to the fan to activate it for around 5-10 seconds...

[racer2086]

I just feel that INPA should activate the fan regardless of the pressures in the car. That just sends direct power to the fan to activate it for around 5-10 seconds...

I agree. But he previously tested with INPA to activate the fan and it didn't (post #7). That is why the next thing he has to test is that the harness ground is good and the PWM signal wire is good. There could be a break in the wire somewhere.

[purplecty]

I agree, which is why the next thing he has to test is that the harness ground is good and the PWM signal wire is good. There could be a break in the wire somewhere.

Yeah that is where I would start...

[rslifkin]

Low A/C charge would cause the high side pressure to potentially not reach the aux fan turn-on threshold, but that shouldn't have any effect on the INPA test.

[Manny G.]

So I retried the INPA test for sanity sake, got nothing. I put a multimeter on the aux fan plug from the body, got 12.5v with the car off, 14.1v with the car on on the power side. My multimeter also allows me to test the Hz and % of a signal, I tested the signal wire, and got 98-99% consistently and bouncing all around 20,30,50,60,100,500 and back down and up in the Hz side.

I picked up a replacement IHKA at the LKQ yard, put it in, coded it, tried, same results.


As a last hail mary, i just started dumping R134a from a small can I had into the low side port. I actually dumped it in UPSIDE down, on purpose. I know its supposed to be held upright, but when I pulled the trigger, nothing was changing. It wasnt until i started the upside down charge that I actually felt the air get a LITTLE cooler! Still no aux fan though.


So right now I'm down to refrigerant charge, ... or even possibly a bad evaporator temp sensor. I'll update when I get the system fully evacuated and charged to see where it ends up.

[rslifkin]

I highly doubt it's A/C system related. INPA should be able to trigger the fan regardless of what the A/C is doing. Heck, INPA will trigger the fan with the key on and engine off.

[Manny G.]

I highly doubt it's A/C system related. INPA should be able to trigger the fan regardless of what the A/C is doing. Heck, INPA will trigger the fan with the key on and engine off.

I agree,... I think I'm facing 2 issues that are overlapping each other at the aux fan. I started to read more on the AC system as well as the over all fan function... one thing that isnt mentioned enough is that the MAF also has an intake air temp sensor and according to TIS, it is also responsible for kicking on the fan. source: https://www.newtis.info/tisv2/a/en/e...sensor/XCkztFG



Intake air temperature sensor

The intake air temperature sensor is integrated in the hot-film air mass meter. In this way, the intake temperature is measured in the same place as the air mass is measured. A precision NTC resistor is used to convert the ”temperature” into a measurement value ”resistance” which can be evaluated electrically by the DME control unit.

For the S62 with MSS52, the intake air temperature is determined only in the hot-film air mass meter I on the left-hand side of the vehicle.

The intake air temperature is used in a large number of DME functions, e.g.

- Calculation of injection volume for cold start

- Determining the ignition angle (timing)

- Knock control adaptation

- Idle control

- VANOS activation

- Activation of secondary air system

- Activation of electric fan

A corresponding fault code is entered in the DME fault code memory if a fault occurs in the temperature sensor. In this case, a fixed programmed substitute value is used for engine operation.


*something* is interfering with the signal to the aux fan but I just dont know what... and it seems to make the car think that the fan is working fine.


Here are my theories:

R134a charge
MAF sensor going bad?
Evaporator temp sensor bad?
AC pressure sensor in drier bad?

then one that I really need to get down and dirty into looking at..

the wiring in the front passenger/right side wheel well above the washer tank. Seems that wiring here gets damaged pretty often, and I can see 1 of the wires for a washer jet is actually showing exposed copper.

[rslifkin]

As far as how well the A/C works or doesn't, does your clutch fan work properly? If so, with a dead aux fan, it should engage the clutch at idle with the A/C on fairly quickly and stay engaged unless you rev it up high enough. And the A/C will work reasonably well without the aux fan provided the clutch fan is working correctly.

[racer2086]

Did you verify the ground wire in the Aux fan harness is good? Without ground, you have an open circuit to the fan and it will never work.

[Manny G.]

Did you verify the ground wire in the Aux fan harness is good? Without ground, you have an open circuit to the fan and it will never work.

Yes, from the fan connector to the body, ground has continuity.

I pulled apart the front passenger wheel well wiring.. the thick ground cable that goes to the washer pump was exposed and another one was pinched really hard. It's the 2 thicker all brown ground wires in that bunch which coincidentally share a ground with the fan. I'm going to spend some time this weekend pulling apart the wire harness and seeing if I can spot anything strange .. then repair those wires and wrap it all up again.

I'm not so sure I've really nailed down what the heck is in the way of the fan turning on though, mainly when the coolant starts to get hot

[Manny G.]

So I might have found my 'smoking gun'. I pulled out and took apart the DME... the front looked OK, but when I pulled off the back piece... well....

I was tracing back the aux fan's PWM wire, .. pin 4 on the DME x6004 connector. Its a Yellow/red stripe wire. I exhausted all possible troubleshooting of the wiring and finally bit the bullet and decided to check out the condition of the DME. I did have fears that there was water damage, I had taken it out a few weeks back but only looked at the front side of it... didnt pull off the back.
Here is the horror show:
IMG_20191216_161928.jpg

IMG_20191216_161932.jpg

IMG_20191216_161937.jpg



I used a boar hair detailing brush to dust off as much corrosion as would fall off easily.. then a mild stainless steel bristle brush to lightly clean the components that had the most corrosion. I did not use any contact cleaners or harsh chemicals. I was able to clean it off pretty good, but sadly, the aux fan is still not working. I'm willing to bet I am going to need a new DME.
IMG_20191216_164038.jpg

IMG_20191216_164051.jpg

[purplecty]

Try and find someone who can clone your original DME so you won't have to replace the EWS and keys and locks too. Another option is to have DUDMD virginize one for you as well...

[Manny G.]

Try and find someone who can clone your original DME so you won't have to replace the EWS and keys and locks too. Another option is to have DUDMD virginize one for you as well...

Good info, I was already looking into what would be done coding wise to replace the DME. Thanks!

[purplecty]

If you get yours cloned then it is just be plug and play as long as you do not turn the ignition switch on after removal of the DME. If you get a used one virginized then you will have to probably just align the DME and EWS using INPA, DIS or ISTA. There are not many out there that can do this but it can be done with special tools...

[Manny G.]

I'm going to go with the cloned route. Already found a replacement on eBay for $44 and printed up the form for DUDMD.

[racer2086]

That board isn't really in that bad of condition. I've fixed worse. You did a decent job cleaning it up, but you need to take a toothbrush and some isopropyl alcohol to remove any remaining contaminants. I hope you didn't go very hard with the stainless brush, as that can destroy delicate traces on the board. Never use a wire brush on a circuit board.

I notice in your picture in the area of the worst corrosion, it looks like you may need to reflow some solder to make good contact again. Specifically, there is solder missing on the pad of the pin that is just to the right of the bundle of traces in your last picture, right where the worst of the corrosion was. Also look closely for any traces lifting off the board. You can re-epoxy them down. If you're handy with a fine tip soldering iron, it may just be worth a shot.

[Manny G.]

That board isn't really in that bad of condition. I've fixed worse. You did a decent job cleaning it up, but you need to take a toothbrush and some isopropyl alcohol to remove any remaining contaminants. I hope you didn't go very hard with the stainless brush, as that can destroy delicate traces on the board. Never use a wire brush on a circuit board.

I notice in your picture in the area of the worst corrosion, it looks like you may need to reflow some solder to make good contact again. Specifically, there is solder missing on the pad of the pin that is just to the right of the bundle of traces in your last picture, right where the worst of the corrosion was. Also look closely for any traces lifting off the board. You can re-epoxy them down. If you're handy with a fine tip soldering iron, it may just be worth a shot.

Going to try the toothbrush with some ISO in a bit.. the highest i have is 91% ISO so I hope that's good enough. I would NEVER intentionally rub a wire brush on a PCB and I definitely did not do that here, .. I'm very familiar with the traces on the board and what a wire brush would do to them. I used the wire brush to clean off the ends of the resistors and some solder spots that had stubborn corrosion on it that would not come off... my aim was to make the solder spots look like solder again and not covered in white.

The spot you mentioned that needed a reflow... I see it too, .. top resistor to the right of the traces just below the row of solder pins from the connector. I actually think that resistor is what directly controls the fan, I'll have to follow the traces from Pin 4 to see where it matches up, but that row of pins soldered to the PCB is actually the row where the x6004 connector plugs in.

I'd love to use a reflow oven, but I dont have one so I'll just have to try touching the solder iron to the end to see if the solder flows to the contact board again. Going to go try that out in a few to see how it goes. I still plan to clone it to another one and add a tune to it.

[racer2086]

Can't hurt to clone it. If you want to send the board to me, I can reflow it. I have a solder station and a hot air reflow station. If you do it yourself, use flux so that you get good flow.

[DeafM5]

is your ambient temperature working correctly (not in MAF) but that sensor fitted under the bumper? Those can affect A/C operation.

[Manny G.]

Can't hurt to clone it. If you want to send the board to me, I can reflow it. I have a solder station and a hot air reflow station. If you do it yourself, use flux so that you get good flow.

I may take you up on the reflow after I have it cloned, might not be a bad idea to have a backup DME on hand.

is your ambient temperature working correctly (not in MAF) but that sensor fitted under the bumper? Those can affect A/C operation.

Yes, the ambient temp sensor reads a normal outside temperature. I am missing the underbody plastic shields that the sensor mounts in, so its currently zip tied nice and neatly on the bracket for the SAP pump just off to the side.


I did notice a strange temp reading when reading the IHKA module through INPA... it said the outside temp was a negative temp... but outside it was actually in the mid 70sF and the ambient temp sensor on the cluster and OBC read normal.


How many temp sensors are there for air temperature on the M62? The MAF, the ambient temp,... and ? Is there another one I'm not aware of?

[racer2086]

Mine also has the bogus reading, yet my ambient temp sensor and the intake air temp sensor are working. I think it's a bug in INPA. I ignore it.

[Manny G.]

So I received the replacement DME.. it's from a 2000 540i. Question, can I simply connect this replacement DME and code it to the 740? Isn't just an EWS alignment or something that needs to be done in INPA? I just want to make sure it's good before I clone my old one to it

[racer2086]

Has it been virginized? You can't just hook it up with your EWS otherwise. You would need to program the VIN and the correct firmware over for your 740. I'm by no means an expert on this, so wait for someone else to chime in.

I'm probably going to be down in your area this weekend moving if you want to hand your original DME board off.

[purplecty]

It may be fully functional for aux fan testing but you may need to flash the 740 software to it. It will not start the car until the ISN has been wiped aka virginized or cloned. After this is when the EWS and DME can be synchronized and the car can be started. It can't hurt to plug it in and test the aux fan with INPA...

[Manny G.]

Has it been virginized? You can't just hook it up with your EWS otherwise. You would need to program the VIN and the correct firmware over for your 740. I'm by no means an expert on this, so wait for someone else to chime in.

I'm probably going to be down in your area this weekend moving if you want to hand your original DME board off.

It has not been virginized. I was thinking that coding it with NCS apply the VIN I need to get the EWS to sync. Also I figured I'd apply the firmware with WinKFP

Thanks but this weekend I wont be around.. heading out of town for the new year tomorrow.

It may be fully functional for aux fan testing but you may need to flash the 740 software to it. It will not start the car until the ISN has been wiped aka virginized or cloned. After this is when the EWS and DME can be synchronized and the car can be started. It can't hurt to plug it in and test the aux fan with INPA...

I think I know where to go with this now.. connecting the replacement DME should at least let me turn the key to position 2, and from there activate the fan in INPA. This should work, thanks for the idea... going to try it out tomorrow morning if i get the chance. It shouldnt affect the EWS negatively when I put the original DME back right?