Overheating Issue, Auxiliary fan?

[Andsman13]

Hello Everyone,

I have a 1989 325is that's been running a little hot lately. especially when driving up hills.. I just replaced my water pump, radiator, fan clutch and hoses. And now i noticed that when I turn the A/C on, the Auxiliary fan doesn't run!. I'm starting to think either the auxiliary fan switch(on the side of the radiator) is bad, or the actual aux fan is faulty. Any thoughts or ideas on how to solve this are most welcome!!!

[spdracrm3]

Fan is controlled by temp switch in end of radiator and only comes on low at 195f low speed and 210f high speed or thru a diode from AC switch turning on low speed relay .so could be signal from AC switch ,K1 low speed relay,Fuse #3 ,low speed fan resistor or fan itself being bad.
You can jumper leads at rad dual temp switch to see if low or high speeds work , jumper GN/BK to BK low ,GN/BK to BK/BR high speed

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[c0rbin9]

Does your temperature kind of slowly creep up? I had a similar issue with a non-working aux fan, but was solved with new thermostat and a thorough coolant flush.

I don't think the car should get hot even with a non-working aux fan, unless something else is wrong. Most of the air is pushed by the clutch fan.

Since you've replaced everything else I would look at your thermostat and a block/radiator flush.

[Ceekers]

As mentioned above either...or both. However, unless you in a hot climate the aux fan doesn't necessarily come on. Or if you run the a/c low speed usually come on to compensate for the load on the system and engine. You may have two separate issues. First thing I would do is get the front of the car on stands or ramps so that the most upper front part of the cooling system is highest. put the heater to full and run the car to op temp and crack the bleeder to see if you still have trapped air. Sounds to me this is the likely case.

As for the aux fan. check fuse first; then if good; maybe your low speed fan resistor is blown. easy to change. with the car off; pull the grille or reach in below and see if you can move the fan blade.
If the blade is stuck your fan is siezed. Sometimes the older model fans can be unsiezed these are the fans with the metal frame. The later model with the plastic frame and curved fan blades are useless. once they go get a replacement.

it is recommended to cycle the aux fan on periodically to prevent siezing especially during winter months if you're in that kind of climate.

[Jeffnhiscars]

Low speed comes on whenever the AC is engaged. If it doesn't, 99% of the time it's the resistor. Either run a hot wire to the fan side of the resistor or, better yet replace the 15a low speed fuse with a 30a, jump the resistor and if (when) the fan comes on just leave it that way. Your AC will thank you.

[Andsman13]

Low speed comes on whenever the AC is engaged. If it doesn't, 99% of the time it's the resistor. Either run a hot wire to the fan side of the resistor or, better yet replace the 15a low speed fuse with a 30a, jump the resistor and if (when) the fan comes on just leave it that way. Your AC will thank you.

Where/ what is the resistor???, I'm familiar, however with the fuses and will check on those soon... Thanks for the response!!

- - - Updated - - -

Does your temperature kind of slowly creep up? I had a similar issue with a non-working aux fan, but was solved with new thermostat and a thorough coolant flush.

I don't think the car should get hot even with a non-working aux fan, unless something else is wrong. Most of the air is pushed by the clutch fan.

Since you've replaced everything else I would look at your thermostat and a block/radiator flush.

Yea the temperature stays at 1/4 while drive and sometimes creeps up to 1/2 or beyond, ill take a look at the thermostat and see if any air is trapped in the system. Thanks!!!

- - - Updated - - -

Fan is controlled by temp switch in end of radiator and only comes on low at 195f low speed and 210f high speed or thru a diode from AC switch turning on low speed relay .so could be signal from AC switch ,K1 low speed relay,Fuse #3 ,low speed fan resistor or fan itself being bad.
You can jumper leads at rad dual temp switch to see if low or high speeds work , jumper GN/BK to BK low ,GN/BK to BK/BR high speed

Sent from my SM-G360V using Tapatalk

I'll check my fuses and test the temperature switch when i have time, thanks for the ideas!!

- - - Updated - - -

As mentioned above either...or both. However, unless you in a hot climate the aux fan doesn't necessarily come on. Or if you run the a/c low speed usually come on to compensate for the load on the system and engine. You may have two separate issues. First thing I would do is get the front of the car on stands or ramps so that the most upper front part of the cooling system is highest. put the heater to full and run the car to op temp and crack the bleeder to see if you still have trapped air. Sounds to me this is the likely case.

As for the aux fan. check fuse first; then if good; maybe your low speed fan resistor is blown. easy to change. with the car off; pull the grille or reach in below and see if you can move the fan blade.
If the blade is stuck your fan is siezed. Sometimes the older model fans can be unsiezed these are the fans with the metal frame. The later model with the plastic frame and curved fan blades are useless. once they go get a replacement.

it is recommended to cycle the aux fan on periodically to prevent siezing especially during winter months if you're in that kind of climate.

Thanks for the information!! I'll have to check the aux fan to see if it is seized. And im in Southern California so it really isn't too hot during the day right now. I will however make sure to check if there is any air in the system. Thanks again!

[Jeffnhiscars]

You really risk wasting a lot f time if you don't check the resistor first. It's mounted to the fan

[mmark.]

I dislike disrupting the thread, but I would recommend that you test for hydrocarbons in the coolant, and check for coolant in the engine oil.
...After your cooling fan tests.

m

[Andsman13]

I dislike disrupting the thread, but I would recommend that you test for hydrocarbons in the coolant, and check for coolant in the engine oil.
...After your cooling fan tests.

m

Thanks, I will definitely take that into account!!

[Jesus12]

Question. I have 03 325i i tried 2 clutch fans and it still wont engage even when overheating. What can cause this? New radiator and water pump

[B320i]

Question. I have 03 325i i tried 2 clutch fans and it still wont engage even when overheating. What can cause this? New radiator and water pump

Could be there is a lack of airflow in the centre of the radiator, so the bi-metal on the front of the fan-clutch will not correctly sense temperature.

Have you done the "newspaper test" with the fan?

May also be the two fan clutches you tried were bad (new or used?), if they were previously good, improper storage can cause the silicone working fluid to leak out.

[Escaport]

Low speed comes on whenever the AC is engaged. If it doesn't, 99% of the time it's the resistor. Either run a hot wire to the fan side of the resistor or, better yet replace the 15a low speed fuse with a 30a, jump the resistor and if (when) the fan comes on just leave it that way. Your AC will thank you.

Jeff, I had the same issue here. I just jumped the resistor and my fan now works. What's the downside of doing this? What purpose in this instance does the resistor serve? Is it so the high speed can kick on when there is no active low-speed?

I had wired in two new resistors (Bosch and the other brand) trying to fix this, but neither worked. Apparently my fan is an aftermarket unit and it's resistor is different. The jump got it functioning.

I'm just wondering if there is an aspect of this fix that's going to bite me in the ass later. I have a new fan on it's way to me, but if this will work with no downside then I'll just return it and keep the couple $100 for other parts for the car.

[Escaport]

I realize now after thinking about it, the resistors is only there to slow down the fan. So essentially I'm running in high-speed the entire time. I guess the only downside is extra noise.


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[Jeffnhiscars]

I realize now after thinking about it, the resistors is only there to slow down the fan. So essentially I'm running in high-speed the entire time. I guess the only downside is extra noise.


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This is correct, but the noise is really only noticeable at idle with the upside being it cools better and your AC will be more efficient. Keep in mind also that there are 2 radiator sensors that also can trigge the aux fan independent of the AC. Both are intended to prevent over heating but I've never heard of the high fan achieving that or of either actually,kicking in to accomplish something.

if you are getting a new fan get a SPAL 14" curved pusher (or equivalent) and run it on high only. It's not as noisy and you get the advantages mentioned.

[Escaport]

This is correct, but the noise is really only noticeable at idle with the upside being it cools better and your AC will be more efficient. Keep in mind also that there are 2 radiator sensors that also can trigge the aux fan independent of the AC. Both are intended to prevent over heating but I've never heard of the high fan achieving that or of either actually,kicking in to accomplish something.

if you are getting a new fan get a SPAL 14" curved pusher (or equivalent) and run it on high only. It's not as noisy and you get the advantages mentioned.

Actually, the noise isn't that bad, and since it's working I'm just going to return the fan I have on order.

Seems I'm back up and running with A/C. Yay! I spent most the day yesterday out in near 90 degree weather and in stop and go traffic. Temp never moved off of 12 o'clock on the gauge, when last week I was fighting every stop to keep from over heating. Seems all good now, but I also found a fantastic deal on a Mishimoto radiator, so I'll be adding that too.