BMW E90 320D (N47) Only Fans

Druza · 2026-02-16T11:52:00+0000

Hi guys, hope you’re all well.

I’m looking for some advice regarding my BMW E90 320D (N47).

The radiator fans seem to be kicking in earlier than expected. After driving about 12–13 km (normal driving, no traffic), both fans come on ….even with the aircon switched off.

We’ve run a full diagnostic and there are:

No fault codes
No overheating
No sensor faults
No coolant leaks
Coolant is circulating properly (water pump is working)

The car is not running hot, which is what makes this confusing. Everything appears normal, yet both fans activate consistently after that distance.

The vehicle does not have a DPF.

Has anyone experienced something similar on an N47? Could it be thermostat-related, fan control module or something else I should be looking at?

I’d really appreciate any advice or direction. I’m honestly scratching my head trying to figure this one out.

Thanks in advance 👍🏼

NBN · 2026-02-16T16:39:29+0000

Not what I was expecting when I saw the phrase "Only fans" in the title 😂

KPM3_30 · 2026-02-16T17:05:30+0000

NBN said:
Not start I was expecting when I saw the phrase "Only fans" in the title 😂

Sorry man, that was me.. Figured more clicks = more potential assistance, also it made me chuckle lol.

NBN · 2026-02-16T17:19:53+0000

KPM3_30 said:
Sorry man, that was me.. Figured more clicks = more potential assistance, also it made me chuckle lol.

Lol you could've said Radiator or Aux fan, not "only fans" 😜

Druza · 2026-02-17T07:09:59+0000

KPM3_30 said:
Sorry man, that was me.. Figured more clicks = more potential assistance, also it made me chuckle lol.

Thank you.

AshG108 · 2026-02-17T11:33:14+0000

Here I thought someone would have a chick from OnlyFans posing with the car or something... lol

Benji · 2026-02-17T11:35:20+0000

Unstimulating

Benji · 2026-02-17T11:39:03+0000

Druza said:
Hi guys, hope you’re all well.

I’m looking for some advice regarding my BMW E90 320D (N47).

The radiator fans seem to be kicking in earlier than expected. After driving about 12–13 km (normal driving, no traffic), both fans come on ….even with the aircon switched off.

We’ve run a full diagnostic and there are:

No fault codes

No overheating

No sensor faults

No coolant leaks

Coolant is circulating properly (water pump is working)

The car is not running hot, which is what makes this confusing. Everything appears normal, yet both fans activate consistently after that distance.

The vehicle does not have a DPF.

Has anyone experienced something similar on an N47? Could it be thermostat-related, fan control module or something else I should be looking at?

I’d really appreciate any advice or direction. I’m honestly scratching my head trying to figure this one out.

Thanks in advance 👍🏼

In 2026 we have this tool called AI. I copied and pasted your exact query and have been a lot more helpful than the distinguished gentlemen on this forum

Use at own risk, always verify AI "opinions" etc

On the N47, fan activation is not triggered only by coolant temperature. It’s influenced by:

Coolant temp
Engine oil temp
EGR temperature
Charge air (intercooler) temp
ECU thermal strategy
Regeneration logic (not applicable here since no DPF)

Since:

✅ No fault codes
✅ No overheating
✅ No coolant issues
✅ No DPF
✅ No AC request

…this narrows it down to control strategy or temperature bias.

🔎 First Question (Very Important)

Are the fans:

Running at low speed only, or
Running at full jet-engine high speed?

Low speed after 10–15 km is often normal.
High speed is not.

🌡️ What’s Most Likely Happening

1️⃣ Thermostat Slightly Lazy (Very Common on N47)

The N47 uses:

Main thermostat (~88–92°C target)
EGR thermostat

If the thermostat is opening slightly early or not regulating tightly:

Engine may sit at 82–85°C instead of 90–95°C
ECU compensates by triggering fan to stabilize temperature window
No fault codes will be logged

Even if it’s not overheating, the ECU may see:

“Temperature curve not as expected” → Fan assist

Check This:

Use live data and monitor:

Coolant temp during cruising
Coolant temp when fans kick in

Healthy N47 operating temp:

88–96°C steady once warm

If you're seeing:

75–85°C → thermostat issue
100°C+ → airflow or radiator issue

2️⃣ EGR Cooler Heat Load (Common on N47)

The N47 runs hot EGR systems. Even without DPF:

EGR cooler can dump heat into cooling circuit
After steady driving, coolant heat load builds
Fans activate to manage EGR cooling

This often happens around:

10–15 km mark
Once full operating temp reached

This is especially common if:

EGR thermostat stuck open
EGR cooler partially restricted

3️⃣ Charge Air / Intercooler Temperature Strategy

Even without AC:

High intake air temp can trigger fan support
Happens especially in warm climates (you’re in South Africa)

After 10–15 km:

Engine bay heat soak builds
ECU activates fan for thermal control

Totally normal if it’s low speed.

4️⃣ Fan Control Module Behaviour

The E90 electric fan is PWM-controlled.

Sometimes:

The fan module slightly drifts
It activates earlier than ideal
No codes are stored

If fan speed is smooth and proportional, likely normal.

If it suddenly jumps to high speed → investigate further.

🔬 What You Should Log (Important)

Using live diagnostics, monitor:

Parameter	What You Want
Coolant temp	88–96°C
Oil temp	95–110°C
EGR temp	Stable, not spiking
Fan activation %	<30% normal low speed

Tell me the coolant temp when fans come on — that’s key.

🚨 When It’s NOT Normal

It’s abnormal if:

Fans run at full speed constantly
Coolant temp stays below 80°C
Coolant temp exceeds 100°C
Fans stay on long after shutdown

💡 Quick Practical Test

Tomorrow morning:

Start cold.
Drive gently.
Monitor coolant temp.
See exactly what temp fans activate.

If fans come on at:

92–96°C → perfectly normal
80–85°C → thermostat likely lazy
100°C+ → airflow issue

🧠 Important Note About “Both Fans”

Your E90 actually has:

One main electric fan
Secondary auxiliary stage control

If you’re hearing “both fans,” it may just be:

Multi-speed stages of the same fan

🛠️ Most Common Fix on N47

If I had to bet based on experience:

70% chance: thermostat slightly off
20% chance: completely normal operation
10% other (fan module or airflow issue)

The N47 is well known for thermostat regulation drift without codes.

BMW E90 320D (N47) Only Fans

Druza

Member

NBN

Well-known member

KPM3_30

Moderator

NBN

Well-known member

Druza

Member

AshG108

///Member

Benji

Well-known member

Benji

Well-known member

🔎 First Question (Very Important)

🌡️ What’s Most Likely Happening

1️⃣ Thermostat Slightly Lazy (Very Common on N47)

Check This:

2️⃣ EGR Cooler Heat Load (Common on N47)

3️⃣ Charge Air / Intercooler Temperature Strategy

4️⃣ Fan Control Module Behaviour

🔬 What You Should Log (Important)

🚨 When It’s NOT Normal

💡 Quick Practical Test

🧠 Important Note About “Both Fans”

🛠️ Most Common Fix on N47

Similar threads

BMW E90 320D (N47) Only Fans

Member

Well-known member

Moderator

Well-known member

Member

///Member

Well-known member

Well-known member

🔎 First Question (Very Important)​

🌡️ What’s Most Likely Happening​

1️⃣ Thermostat Slightly Lazy (Very Common on N47)​

Check This:​

2️⃣ EGR Cooler Heat Load (Common on N47)​

3️⃣ Charge Air / Intercooler Temperature Strategy​

4️⃣ Fan Control Module Behaviour​

🔬 What You Should Log (Important)​

🚨 When It’s NOT Normal​

💡 Quick Practical Test​

🧠 Important Note About “Both Fans”​

🛠️ Most Common Fix on N47​

Similar threads

🔎 First Question (Very Important)

🌡️ What’s Most Likely Happening

1️⃣ Thermostat Slightly Lazy (Very Common on N47)

Check This:

2️⃣ EGR Cooler Heat Load (Common on N47)

3️⃣ Charge Air / Intercooler Temperature Strategy

4️⃣ Fan Control Module Behaviour

🔬 What You Should Log (Important)

🚨 When It’s NOT Normal

💡 Quick Practical Test

🧠 Important Note About “Both Fans”

🛠️ Most Common Fix on N47