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Engine fan does not engage

23K views 29 replies 5 participants last post by  BMW-North 
#1 · (Edited)
Problem description:
The fan (engine cooling) does NOT engage when it should. Actually the fan never engages even when the temperature rises towards the red zone. I already had an overheated car twice after I got stuck in a traffic jam.

What did I do already?
A couple of parts have been replaced. A complete new fan together with the control module (I think you cannot even buy it separately actually). Also a new temperature sensor is in place (the coolant sensor in the lower radiator hose). Last but not least recently (two weeks ago) also a new thermostat is placed.

At first we thought the fan would not go on simply because it might be broken. Well, it turns out it is not since the new fan still does not engage when the coolant temperature gets above 105 degrees Celsius. The fan does have the required voltage on provided, and the signal wire (PWM) also seems to be alright. The t-stat opens when it should, and afterwards the lower hose noticeable gets warmer, also the sensor value indicates a higher temp. when this happens - all good.

Since yesterday I do have some diagnosis capabilities (INPA and DIS) and I ran the 'electric fan' test a couple of times. Directly after I start the test the fan engages to full speed for ~30 seconds. So for that part everything seems OK. There is an error saved in the DME module though, it reads:

"(108) 6C Activation, electrical fan". Furthermore it says "Open circuit" and that the error is currently available.

The error returns directly after I clear the error memory - this must be related. I also check all the fuses and visually inspected the cables running from the fan / temp. sensor back to the front of the car.

What do we know:
  • Testing the fan with diagnosis software works.
  • Values from both the temp sensors in DIS look OK when running the car.
  • Fan, coolant temp. sensor and t-stat is all new.
  • Error 108 keeps returning in DME.
  • Fuses are all OK.

I do not know where to look anymore. Is there anything else I could try/test to isolate the problem? Could it be the DME that is failing (I hope not)?

edit: The car is a E46 - 316 1.9 (2001-01) M43 engine.
edit2: It's a manual transmission. This means it has not pusher fan, only one electrical (radiator) fan.
 
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#2 ·
Did you check the connectors on the harness to the fan, as in the contacts? Maybe its not able to read a signal from the fan that lets the computer know when its been engaged and what rpm its running at?

Id clean the contacts, and possibly check on crimping the pins slightly to start with. Also, your aux fan may be the actual culprit from what Ive read in the past.
 
#3 ·
Yes I did check a lot of connectors and cleaned them as well (including the ones related to the fan). I do not know if the DME is actually aware of the fan running or not. I do know that the signal wire carries an PWM signal that instructs the fan's control unit to engage and at which speed. This signal cable works I guess because the fan test I ran via DIS makes the fan engage at full speed.
 
#4 ·
Check any relays associated with both the pusher fan and the cooling fan. Ive never had this problem before so I personally cant give any exact answers. Maybe someone with similar experience in the past will come along and help.

I had a similar situation with my oldsmobile, faulty relay would work sometimes, more often not.

To me it can only be so many things. Whatever controller board sends the pulse width modulation signal, relays, fuses, the fan itself, temp sensor, aux fan (pusher fan) being busted causing a domino effect possibly.... etc

My guess is still the connectors, I would check the pusher fan connectors also, if you havent already.

Hope you get it sorted.
 
#6 · (Edited)
I forgot to mention that I have a manual transmission, and those do only have a single (radiator) fan. There is no pusher fan on those models. Also there is not any relay as far as I know. The fuses are all checked and good. The fan and temp sensor both are replace and the problem still persist. I agree that perhaps the board which controls the PWM signal is faulty. That must be the DME module.

I think that may be why you are getting open circuit errors, something may not be getting the signal it is expecting.

If it doesnt end up being something simple or a sensor, it "might" be whatever controller board hosts the transistors/mosfets used for the PWM?
I think so too. That would be the DME module controlling the PWM signal. One of the main modules (and most expensive). But the fact that when I connect my car to the diagnosis software (DIS) and run the 'electric fan test' with success makes me doubt that there is something wrong with the PWM signal. I do not have a oscilloscope but the voltage does change on the signal wire when running the test (the fan also spins at full speed). Thanks for you input, appreciate it.
 
#9 ·
I took the liberty to look at some schematics for you. Have you checked fuse f37 with the 50A fuse? That seems to be part the electric fan system.
 
#10 ·
another question, i'm assuming that when you say electric fan mod, this car originally came with the mechanical fan correct? or no? if it did, there also wasn't any other fan like say the ac fan also correct? also take a look at this screen shot.
 

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#11 ·
From what I can tell, the DME just completes the circuit using ground, not sure why that would be an extremely expensive part. Didnt see anything for a signal from the fan, back to the DME.

On a side note, after doing some reading, another BMW owner had the same situation and resolved it by bleeding the cooling system. Seems there was an air pocket or something that caused his fan not to turn on.

Another owner solved by switching the temp sensor, and another resolved with a new fan lol. But since you already replaced those...

Weird. Seems like a pretty simple system, you would think the problem would be extremely apparent.
 
#13 ·
perhaps that should be what he should try to make sure the signal is returning back to the dme. the diagram states that the dme has 1 wire that leads to temp sensor and the 2nd wire from temp sensor goes right back to dme. from there, the dme sends another wire out to the electrican fan, which combined with a wire leading from fuse 37 for power and i'm sure at least another wire for ground should complete its circuit.
 
#14 ·
I'm sure wondering whether the car originally came with an electric fan or not. I've noticed that e46s sold outside the US tend to lack prewired connections for future additions, an example being the alarm security system. if you didn't ask for it when it was 1st bought, the wires for them aren't there. this could be one of those situations.
 
#15 · (Edited)
Check for this:

1. Does the fan spin (briefly) when the key goes to position 2? It is part of the self check? It will then stop till it gets another signal (usually temp or ac related)

2. Does the fan spin when the engine is running and you turn on the ac compressor (on the manual trans - this activates the fan via the aux fan relay (AFR) module)

If both are no - it would appear a bad fan control module but you said you changed that?

In a worst case scenario you can use the old fan - bypass the fan control module and just send a constant 12v to the electric fan - this will stop overheating and let you drive the car till you can diagnose the real cause.

If the AFR is good then I would suspect the ECM may not be sending the signal - it is difficult to determine but can be done.

3. Check these prior threads:

http://www.e46fanatics.com/forum/showthread.php?t=851978

http://forum.e46fanatics.com/showthread.php?p=13516820
 
#18 ·
If both are no - it would appear a bad fan control module but you said you changed that?
Thats whats bad about some situations, you can replace the part, only to find out later that it was defective. I hate those situations.

I think its air in the cooling system or a break in the wiring somewhere. Those tests mentioned above (Removing the temp sensor connector to see if the fan kicks on etc) are a good place to start, along with what BMW-North mentioned also.
 
#17 · (Edited)
not necessarily. perhaps he may have been right on time to hop on the bandwagon for electric fans on manuals but they didn't always come that way.
 
#21 ·
I would suspect the relay. Relays can be intermittent and do have a limited life span.

Have you run the car in your driveway at idle to see if it comes on? Is it truly intermittent or does it fail to come on each time under traffic/idle conditions


Sent from BimmerApp mobile app
 
#22 ·
Which relay do you mean? I am not aware of any relay in this specific circuit. I only checked fuse 37 (50A). Note that the fan does engage when I run a test via DIS (diagnostics software).

Yes, lately all tests are being done idling in the garage. We wait till the car reaches normal operating temperature and then we start monitoring closely. We see both coolant sensors (on the engine and the one on the lower radiator hose) reporting increasing temperatures.

When the temperature gets >105 degrees Celsius the radiator starts to 'steam' since it isn't being cooled down (overheating starts). A little after this point we shut the engine off since the fan should have engaged already.
 
#23 ·
Post #10 screen shot referenced a relay, I see now that it is for the e36 not e46.

Steam should not come from the radiator at 105c. This tells me that it is either wet from previous overheats or it has a leak. The car should operate all the way to 113 before the gulags comes off of dead center without steam.

Will think on it some more and post if I have any other ideas.

GL


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#24 · (Edited)
So, to summarize:

- The fan itself is OK (replace with new unit).
- The fan control unit is OK (part of the fan assembly replacement, see above)
- There is a +12v DC on the fan, the PWM signal cable is also present.
- Wiring seems to be OK since the DIS electric fan test runs OK (fan spins for 30 seconds).
- Lower radiator hose temperature sensor is OK (checked reporting value with DIS + the sensor is new)
- All fuses are OK, also fuse 37 (50A). (otherwise the diagnostics test would also fail)
- For what it is worth water pomp and thermostat are also replaced/new.
- System is properly bleeded, hoses are all nice and clean - no leaks
- Error code 108 is still thrown '(108) 6C Activation, electrical fan'

Tomorrow I run a couple of more test. What happens when I disconnect the coolant temp sensor while the engine is running (fan should engage?) and if the fan spins briefly after I start the car. Is there something to test in regard to the DME? How big is the change the cause of the problem lies within the module (taking in mind the DIS test that does work)?
 
#25 ·
Check the coolant sensor wiring. One of the wires may be broken inside the sheathing and making intermittent or no contact - even though the sensor is new and good. The DIS would not need this wiring intact to send a test PWM signal to the Aux Fan Relay.

However if the sensor wiring is working you should be able to read live data including coolant temperature

You may need to short the wiring to test a PWM signal to activate fan not just remove the sensor.
 
#28 · (Edited)
DIS does show live data of the coolant temp sensor. The reported temperature values by the coolant sensor seem realistic. I assume that the sensor and its wiring is OK.

Later today I will run the test of disconnecting the coolant sensor while the engine is running, just to see what happens.

I did a lot of research on the WDS system (wiring diagrams) but there is not a lot else I can test. Does anyone have experience with opening the DME and testing the parts inside (with a multimeter or so?).

Interesting is that the description of the wire running from the fan module to the DME is described as 'T_ELUE' or 'Activation, electrical fan' in WDS. This almost equals the error description I am getting. The error message has 'open circuit' appended so my guess is still something related to the wiring / module is off. Not really a clue on how to test the DME or its inner parts though (can you even open the DME?).
 
#26 ·
I dont think disconnecting temp sensor in lower hose while engine running is a good idea. If it does pop on, not much wiggle room or clearance
 
#29 · (Edited)
Update (positve)

Did some tests today:
  • First thing I tested is running car and disconnecting the coolant sensor. Result? The fan engaged at full speed shortly afterwards.
  • Secondly, I connected my old fan assembly (so with the fan relay) to the car. Then I ran the fan test via DIS. The result was that the fan made an attempt to spin up, but directly come to a full stop again. This repeats continuously. With the new fan the test does run without problems. Conclusion? The old fan assembly is indeed broken (or at least the fan relay / module is).

So I did put everything back together and started up the car. I let it idle until it reached about 105 degrees and notice the thermostat opened. After a little while the (lower hose) coolant sensor temperatures started climbing. At 90-93 degrees at that sensor the fan was given 10-13% speed from the DME (checked with DIS) - and indeed, the fan started engaged! Rapidly after the fan engages the coolant temp drops till 60 degrees and the fan switches off.

All seems to work good - BUT - there is still the error code present in the DME I mentioned before (108 Activate electrical fan - open circuit). However, the fan and the DME do communicate, and the fan does get activated properly...

Could it be that since the fan is an aftermarket one (brand reads TYC) it's module/relay is not fully compatible with the DME so it writes an error code? Thank you guys so much for your help and great ideas!

EDIT: Just stumbled upon this: http://www.bimmerfest.com/forums/showpost.php?p=6962660&postcount=4. Apparently this guy also installed some aftermarket fan which kept returning the activation error. He resolved it by replacing the aftermarket fan by an OEM / BMW unit (which is twice as expensive). As long as my cheaper fan works I could just ignore the error right?
 
#30 ·
Glad you were able to confirm the fan is kicking in when it should. This will avoid any major overheating issues. I use an aftermarket fan in two manual e46's (325 & 330) - no errors. Actually I don't use the whole fan shroud assembly - I used only the Aux Fan Relay Module - I bought the cheaper aftermarket unit only for the AFR since the OEM has proven itself no better only lasting a few years on each vehicle. I mount the aftermarket AFR on the old shroud and use the OEM fan & motor (which is a Bosch unit).

BTW if you search for one of my prior threads you will find one where I describe buying the Fan Shroud assembly for an Automatic E46 and using it on the manual tranny cars by moving the fan motor & AFR to your old shroud. For some reason the automatic fan assembly is priced cheaper (was at that time) but has exactly the same components as the manual tranny fan. If your shroud is in good shape you can just move everything over.

I also recall when the AFR fails it gives a very clear error code that it has failed Something like AFR Unit Failure - not the 108 error that you are reading. Just monitor the car for a wee while but I think you are fine. Good job.
 
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