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Without access to INPA is there a way to test the aux fan direct outside of the care. Example checking a spare used?
Not sure I got your full question. The simple way is to turn the AC on with the car warm. Depending on the model year and package it will turn on immediately or there might be a short delay, but it is short. My guess is the later cars use more of the other two sensors that watch the AC system.
Don't think we ever got to testing the supply control voltage to emulate what controls the speed. You need an oscilloscope for that, I am sure this was on 68's list but don't remember him doing it. My tests with a 9v battery did not yield expected results. So as far as I know we have no idea if a short pulse makes the fan run slower or faster. A near 5v constant signal might make it run slow, or a slow pulse of 5v might do that.
Really all you can do is run the AC and see if it works. We also have no idea what the car uses to decide what speed to run the fan at, there are two pressure sensors on the AC, then there is the lower coolant output temp sensor, and last road speed that come into play. If you are having issues with the AC, or road speed sensors, and don't have the cold weather package or you car is later than the official change to the 3 wire system, your results may vary.
That said turning on the AC with the car parked in the drive warm has been a reliable way to find many a bad fan, before they start the burning up process because it seems pretty clear the lower speeds go first even though full speed may last for a longer time before it fails.
My suspicion is the damage to the fuse and wiring happens when only the full speed is working, but that is just a guess from where the damage has been found on the board posts.
 

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Not sure I got your full question. The simple way is to turn the AC on with the car warm. Depending on the model year and package it will turn on immediately or there might be a short delay, but it is short. My guess is the later cars use more of the other two sensors that watch the AC system.
Don't think we ever got to testing the supply control voltage to emulate what controls the speed. You need an oscilloscope for that, I am sure this was on 68's list but don't remember him doing it. My tests with a 9v battery did not yield expected results. So as far as I know we have no idea if a short pulse makes the fan run slower or faster. A near 5v constant signal might make it run slow, or a slow pulse of 5v might do that.
Really all you can do is run the AC and see if it works. We also have no idea what the car uses to decide what speed to run the fan at, there are two pressure sensors on the AC, then there is the lower coolant output temp sensor, and last road speed that come into play. If you are having issues with the AC, or road speed sensors, and don't have the cold weather package or you car is later than the official change to the 3 wire system, your results may vary.
That said turning on the AC with the car parked in the drive warm has been a reliable way to find many a bad fan, before they start the burning up process because it seems pretty clear the lower speeds go first even though full speed may last for a longer time before it fails.
My suspicion is the damage to the fuse and wiring happens when only the full speed is working, but that is just a guess from where the damage has been found on the board posts.
Thanks. That was a great response. The car is a MY01 E39 M5. Max ac did not cause a change. I tested with another Fan know to be good. However because it's used couldn't reall rule the fan out yet. Voltage at the fan was about 11.5v. Ac and car on. Just figured there was a way to bypass whatever it is to rule out the Aux fan itself as the source.
 

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Just figured there was a way to bypass whatever it is to rule out the Aux fan itself as the source.
The volts are too low unless the battery is low so you might have the full blown issue. Sometimes the fuses don't blow just melt the holder and cause resistance, and then there is the damage that can happen to the wire. I think you need to follow the link in my thread to sleepers thread. His car was far worse than mine and he gave some good steps on how to figure it out.
 

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Discussion Starter · #24 ·
I've had a similar issue this year, but my aux fan does work. I can confirm Shady/others are correct in that the aux fan does more. While trying to diagnose, I drove the car for an entire day this fall (mid 60's F) without the mechanical fan installed. I had pretty much the same operating temps in slower speed driving. It gets into the low 90's C. I'm sure it would go higher if I kept idling and moving too slow to move enough air across the radiator.

Turns out my issue is the radiator, which I was suspecting even though it's only 7-8 years old. Not enough flow at low speed and idle in traffic. I had already removed it and cleaned debris at the end of summer. It helped a bit but now I have the smoking gun - the radiator started to distort - it expanded the core. Internal clogging is my guess.

Since you're going to replace the fan, you'll have a chance to review the radiator condition. If you're hitting over 100C, you might suspect more than just the aux fan. As you know, best to replace one thing at a time though.
Hey, so the radiator is brand new. Less than a month. Its a behr which lately behr products have been sh1t not genuine bmw. I have installed a new electrical fan and it works, it did make quiet a big difference during traffic but car still runs at 95 deg celcius oil passes middle mark when cruising
 

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Discussion Starter · #25 ·
UPDATE!
APOLOGIES FOR NOT USING FAHRENHEIT numbers, i am in Canada, it takes to long to convert everytime.
OK SO, UPDATE. I replaced electric fan It does come on now in traffic, now the coolant temp goes up to 95 degrees Celsius (before used to go up to 110-112) so that takes care of one issue, that tells us that the electric fan does play a bigger role than the fan clutch in an S62 car.
2. I have drained the coolant from the block and the radiator. I have warrantied the already new thermostat and waterpump, i have removed the new radiator and connected a water hose to it to check if flows well, no issues there.

3. Everything back together, drove the car on the highway and streets, oil temp still tries to pass the middle mark sometimes, not always when cruising with or without traffic, and also coolant temp is still too high at 95 degrees, it is cold af outside, it should be 90 or below, i've had so many of those cars, i know this isn't right. The electric fan is on almost all the time now during street/traffic lights driving, shouldn't be happing when it's +5 celsius outside, in summer when it'll be +25 i feel the car will struggle to keep temps down.

CONCLUSION: The only thing left to do at this point is to replace the heat exchanger. When i rebuilt the engine i cleaned it properly with hot water, checked for flow or debris, none found. AFTER this i am clueless. Feels like a very minor restriction of flow somewhere. Anyone ever replace oil filter housing?
 

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CONCLUSION: The only thing left to do at this point is to replace the heat exchanger. When i rebuilt the engine i cleaned it properly with hot water, checked for flow or debris, none found. AFTER this i am clueless. Feels like a very minor restriction of flow somewhere. Anyone ever replace oil filter housing?
That does not add up. First I would check that the previous owner has not got into the software and changed the buffer for the temp sender. Those gauges are meant as idiot switches and are buffered. If the buffer was removed it might report minor changes that were normal but unseen with the standard software. The other thing to check is the plug that connects to the temp sender. More than a few owners have had to lightly coat the pins with solder because the plug does not make solid contact. I forget the details and symptoms but there are some threads. 68FB discovered that and opened at least one thread on it so search his handle in the search.
Your problem is either air flow or water flow. Maybe the tensioner is weak and at low RPM the belt slips a little. I doubt that but the heat exchanger seems like a stretch. The heat exchanger is working on partly heated coolant and there is a time function there too. It also seems to work since both temps go up together.
Next time you are rolling to a stop bring the RPM up a bit which will raise the water flow and should change things. If there is a noticeable change that would point to water flow rather than air. That said increased rpm should produce more heat so if it is an air flow problem the temps should get hotter, but watch how fast those changes happen. The speed at which those changes happen may support the idea that your buffer has been removed, which is still my bet.
Edit I am still thinking about the #3, might change my bet to a poorly connected sender as that seems to be erratic and I believe that is the number one word used to describe that problem.
 

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Having my problems getting my head around this issue. It might be a couple of things together. No idea what, but we will get there. So lets do some checks, the first is open the secret menu and put Ktemps up and compare that to your gauge always, you might be doing that already, but state it. Two of the pins from the sensor feed the gauge and two feed the Ktemp reading, basically. The Ktemp is not buffered. When you first start the car cold and watch the temps you should see when the t-stat opens. When the T-stat opens it dumps a bunch of cold coolant into the system. If the buffer has been removed you will see a drop in the gauge, if it is still there the gauge just sort of hangs a little under 80 or normal position. The Ktemp will drop. Again read both the gauge and Ktemp you could also look at the oil temp but I forget which that is in the secret menu.
Also pay attention to the time that it takes for startup to the t-stat opening and then when that become stable indicating the coolant is all at the same temp. I think it is 5 mins to open then 7 to become stable. Also note when you get warm air out of the vents. Maybe this is the heater valve being frozen, just pulling strings. Next when you see the temp rise at some point crank the cabin heat up and turn the fan on high, it is a great uncontrolled rad that can actually make the car run cold this time a year in Ontario. Yes I know your problem is warm but it is a detail. If that has no effect it will say something. Not sure what but we will get there.
Did you replace the T-stat seal when you replaced the T-stat? Usually makes the car run cold but I am just looking for connections and data points. I am assuming you checked the condenser when you had the rad out but if it was plugged that will still effect how much air goes through the rad.
 

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Discussion Starter · #28 ·
UPDATE 2 CAR IS FIXED.
REPLACED HEATER VAVLE WITH AUX PUMP together, Aux pump was not turning on at all. I have no idea how the [email protected] this is related to car running too hot, because as far as i understand it's just for heater while the engine is at idle. But it did fix the main issue so I'm happy. Not a cheap part to replace.

Thanks to everyone for your inputs and trying to help.
 

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I've had a similar issue this year, but my aux fan does work. I can confirm Shady/others are correct in that the aux fan does more. While trying to diagnose, I drove the car for an entire day this fall (mid 60's F) without the mechanical fan installed. I had pretty much the same operating temps in slower speed driving. It gets into the low 90's C. I'm sure it would go higher if I kept idling and moving too slow to move enough air across the radiator.

Turns out my issue is the radiator, which I was suspecting even though it's only 7-8 years old. Not enough flow at low speed and idle in traffic. I had already removed it and cleaned debris at the end of summer. It helped a bit but now I have the smoking gun - the radiator started to distort - it expanded the core. Internal clogging is my guess.

Since you're going to replace the fan, you'll have a chance to review the radiator condition. If you're hitting over 100C, you might suspect more than just the aux fan. As you know, best to replace one thing at a time though.

This also has happened to me. After a hard acceleration, coolant temps would skyrocket, followed by oil temps if I didn't let the car cool down. Turns out mine was clogged by using an incompatible mixture of water, OE coolant, and water wetter additive, which created a nasty sludge. Years later, the sludge is still in parts of the system like the heater core and beginning to do damage in that area to the core.
 

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I have no idea how the [email protected] this is related to car running too hot, because as far as i understand it's just for heater while the engine is at idle.
No it does more than that, in short it redirects coolant depending on a few things but mainly temp. Glad you got it fixed though. The valve is really about pushing the warm coolant from the heads directly into the cab heat on cold startup and times when cab heat is questionable. The outlet for that is right by the temp sender which explains the temps for the coolant going up but not really the oil temps. That will be for another thread.
 
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