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Old 03-21-2009, 12:12 AM   #1
Mercutos
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99 323i radiator fan not running at high speed

Having some overheating problems. I have a 99 323i. It is different than most E46 in that it has only one large electric cooling fan on the back of the radiator. It has no small front fan nor a clutch driven fan behind the radiator. I think they only did this in 99, or 99-00. It uses some sort of transistor or resister to thingy to regulate fan speed. I am not sure if it is really controlled by the ECU. It might be more rudimentry than that.

It has two speeds, or maybe more speeds than that, but it only runs at a low speed.

The car will only overheat if it is hot or if I have been driving hard & then I get stuck idling or crawling, especially when the AC is on or I am on hot black top on a sunny day. But, as soon as I get going down the road it cools off. Or, I have to turn my heater on high to lower coolant temperatures.

I have verified that the problem is that fan not running in high speed when it begins to climb above optimum operating temp. Also, my mechanic, who was not able to fix it, determined that the problem was not that the fan itself can't run on high b/c he put 12v to it & it ran like a scalded ape.

FYI, thermostat has been changed.

I searched the forums & all I could find was THIS

So, what's next. I guess the resistor or transistor thing is suspect??? How can I do some troubleshooting?
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Old 03-21-2009, 04:04 PM   #2
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Is there a temp sensor in a radiator hose that the fan control unit depends on that could be bad?

I should state that the fan doesn't run at all when the car is heating up & then at a certain point it turns on low.
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Old 03-21-2009, 05:57 PM   #3
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yea the fan has the relay for hi n low speeds, they dont sell the relay seperately you would have to purchase an entire new fan unless u can jus switch the relay from a used one or something but instead of going through tha trouble jus swap the entire fan
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Old 03-22-2009, 02:00 PM   #4
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Replace the Radiator Fan

I have a 99 323i Manual.

I had the identical situation with the car overheating in the evening commute when I came to a stop after driving at speed. [Fall 2008]

The first time this happened the radiator expansion tank let go.

I had the expansion tank replaced as well as the water pump and thermostat to avoid future cooling system problems.

But, a few weeks later I had the same problem, ironically in the same place in the evening commute. This time the expansion tank held and the engine temperature returned to normal after a couple of seconds in the red zone so I could drive home.

After this incident the dealer checked the cooling system again and they determined that there was some air that needed to be bled out of the system.

A few weeks later, however, I had the another over heating incident, also in an evening commute when I had to stop for traffic!

The car went in for a third look. This time the service department was able to finally able to isolate the problem to the radiator fan not turning on when the temperature reached the point at which more air flow was needed to keep the engine coolant temperature in spec.

They replaced the radiator fan and I have not had a problem in the cooling system since.

The fan is designed to not operate when the car is at speed assuming the ambient temperature is not too high.

Conclusion: Replace that radiator fan!


Quote:
Originally Posted by Mercutos View Post

The car will only overheat if it is hot or if I have been driving hard & then I get stuck idling or crawling, especially when the AC is on or I am on hot black top on a sunny day. But, as soon as I get going down the road it cools off. Or, I have to turn my heater on high to lower coolant temperatures.

Last edited by mpollard; 03-23-2009 at 11:32 AM.
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Old 03-22-2009, 09:51 PM   #5
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I would hate to buy the whole fan b/c I know it will run on high w/ 12 v on it, but if that's the only way I can get the control unit...

I remember the mechanic telling me that it's not a relay, it a transistor or a resistor.

I just got off of real oem.com & it seems like I can't find the fan. I brought up the radiator fan, but the diagram is showing a pulley driven fan, not the type I have that is sole ele motor driven between the radiator & the engine. How can I get that part number? or did they DQ that in favor of retrofitting the pulley driven & smaller ele fan?

I can't find it on BMA parts either.

Last edited by Mercutos; 03-22-2009 at 10:30 PM.
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Old 03-22-2009, 10:11 PM   #6
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here is the part # 17117561757 its under the radiator section
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Old 03-23-2009, 01:45 AM   #7
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since you already changed your thermostat, your prob is definitely the aux fan, the control unit/motor to be exact. HAD the same problem and had to change my fan! replaced it with an aftermarket one. The problem is the Control unit or the rectangular shaped box attached to the fan housing, mine would not go high speed, it is where the two wires are connected. Unfortunately you can't buy just this part. REplace your fan asap because if not, your aircon compressor would go high pressure that could result to failure. I bought an aftermarket fan which is way cheaper that the genuine bmw fan. It is also german made.
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Old 03-23-2009, 02:14 AM   #8
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who made that fan, how can I find it?
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Old 03-23-2009, 02:14 AM   #9
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Quote:
Originally Posted by GIO_21 View Post
here is the part # 17117561757 its under the radiator section

Thanks for that GIO. That is real swell of you.
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Old 03-23-2009, 06:42 AM   #10
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Quote:
Originally Posted by Mercutos View Post
who made that fan, how can I find it?

brand is vemo....... www.vemo.de
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Old 03-29-2009, 12:25 AM   #11
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thanks for the Vemo link. I saw that Real oem sells the OEM & a Bosh unit. The Bosh unit is a little cheaper.

You all are talking about the main sole radiator fan right, not some small auxilliry a/c condenser fan?

I am wondering if there is a way I can just do it ghetto somehow so the fan willl fan on high constantly when the car is on or something. Or maybe I could get a little 12v relay w/ power & control terminals & run a little control circuit to a switch in the cab & power wiring b/t the fan & the relay...Have to read amps & get sufficient conductor for it of course so I don't make a fire.

I watched the mechanic push on that little relay unit thing w/ a screw driver & kick that thing into high speed. I think he may have just been pushing a bi-metal leaf over onto a contact or something...
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Old 03-29-2009, 12:27 AM   #12
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no all 325 and 323 have that fan if ur talking about the fan right behind the radiator
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Old 03-29-2009, 12:55 AM   #13
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In South Florida you might be okay leaving the fan on at all times. In temperate climates this could cause a problem by cooling too much, since the fan would be pulling air through the radiator at all times, even at startup.

Because the fan is an integral part of the engine cooling system and because you really want this engine to not overheat, consider if you want to fool around with this.

If time is not a factor you might try sending it back to Germany to have the control system swapped out.

It would be nice if there was a field repair for the switch.



Quote:
Originally Posted by Mercutos View Post
thanks for the Vemo link. I saw that Real oem sells the OEM & a Bosh unit. The Bosh unit is a little cheaper.

You all are talking about the main sole radiator fan right, not some small auxilliry a/c condenser fan?

I am wondering if there is a way I can just do it ghetto somehow so the fan willl fan on high constantly when the car is on or something. Or maybe I could get a little 12v relay w/ power & control terminals & run a little control circuit to a switch in the cab & power wiring b/t the fan & the relay...Have to read amps & get sufficient conductor for it of course so I don't make a fire.

I watched the mechanic push on that little relay unit thing w/ a screw driver & kick that thing into high speed. I think he may have just been pushing a bi-metal leaf over onto a contact or something...

Last edited by mpollard; 03-30-2009 at 06:20 AM.
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Old 03-30-2009, 02:11 AM   #14
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It is not a good idea to run the fan on high constantly. your engine is setup to run at a certain temperature. if you run it cooler, then you'll waste more gas and cause more pollution. You won't have heat in the winter either.
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Old 04-04-2009, 08:50 AM   #15
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Awesome, more pollution!

No doubt this would be less than ideal, but remember there is a thermostat b/t the water in the ratiator & the water in the engine to limit how much the radiator fan would cool the water temp in the engine, which is what keep your engine warm enough when you are running down the highway. Summer is coming on for me here though...But yes, it would make the system at least a little less thermally efficient.
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Old 06-30-2010, 03:29 PM   #16
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Ok, I've also got a 1999 323i 5-speed manuel and now since it's summer my car overheats at idle. I've already had the waterpump and thermostat replaced...so I guess it's now time for a new auxiliary fan. Mercurots did swapping out the old aux fan for a new one fix the problem?
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Old 10-01-2010, 07:54 PM   #17
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Quote:
Originally Posted by GIO_21 View Post
here is the part # 17117561757 its under the radiator section
Very nice. Thank you!
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