Help diagnosing radiator fan not turning on

[Kross]

Hi all,

08 e90 m3 + ESS VT595 + do88 big pack

I'm looking for help diagnosing and fixing my radiator fan not kicking on, causing overheating at idle.

I'm only getting 7 volts to the fan plug with the car running and AC on full blast - I blieve I'm supposed to be getting continuous 12v?

I've checked fuse 88 behind the glove box. Looks ok, a little corrosion, 12v+ on both leads.

Not really sure where to go from here, any help is appreciated!

[Brandoch]

Originally Posted by Kross

Hi all,

08 e90 m3 + ESS VT595 + do88 big pack

I'm looking for help diagnosing and fixing my radiator fan not kicking on, causing overheating at idle.

I'm only getting 7 volts to the fan plug with the car running and AC on full blast - I blieve I'm supposed to be getting continuous 12v?

I've checked fuse 88 behind the glove box. Looks ok, a little corrosion, 12v+ on both leads.

Not really sure where to go from here, any help is appreciated!

I can not help you with the circut since I do not have the wiring diagram in front of me at the moment, but... Whenever you see corrosion, deal with that first. Remove the fuse clean up the corrosion. Replace wiring and connectors if need.

[Kross]

Originally Posted by Brandoch

I can not help you with the circut since I do not have the wiring diagram in front of me at the moment, but... Whenever you see corrosion, deal with that first. Remove the fuse clean up the corrosion. Replace wiring and connectors if need.

I appreciate the comment. I don't think it's the cause but to be sure, I have new fuses on the way. I also swapped fuses with other components to no avail.

I'm hopeful for other ideas while I wait.

[DrFerry]

The fan relay (engine radiator fan) is located in the foot well of the passenger front seat... directly in front of the seat under the carpet.
https://www.m3post.com/forums/showthread.php?t=1177827 See screenshot below.
Fuse 28 (5 Amp): This fuse specifically protects the cutout fan relay circuit.
Fuse 37 (60 Amp): Located in the glovebox fuse panel, this provides the main power for the engine cooling fan.
Coolant Temperature Sensor: It is located on the thermostat housing. It monitors temperature and sends a signal to the DME to activate the fan.

A quick way to test the fan's health is to unplug the coolant temperature sensor while the engine is running. If the fan immediately kicks on to high speed, the fan motor and module are likely fine, and the fan relay, temperature sensor or thermostat may be the issue.

Circuit diagram is here:
https://www.m3post.com/forums/showthread.php?t=2074912
.

[Kross]

Originally Posted by DrFerry

The fan relay (engine radiator fan) is located in the foot well of the passenger front seat... directly in front of the seat under the carpet.
https://www.m3post.com/forums/showthread.php?t=1177827 See screenshot below.
Fuse 28 (5 Amp): This fuse specifically protects the cutout fan relay circuit.
Fuse 37 (60 Amp): Located in the glovebox fuse panel, this provides the main power for the engine cooling fan.
Coolant Temperature Sensor: It is located on the thermostat housing. It monitors temperature and sends a signal to the DME to activate the fan.

A quick way to test the fan's health is to unplug the coolant temperature sensor while the engine is running. If the fan immediately kicks on to high speed, the fan motor and module are likely fine, and the fan relay, temperature sensor or thermostat may be the issue.

Circuit diagram is here:
https://www.m3post.com/forums/showthread.php?t=2074912
.

Thank you!! I'll check these fuses and the relay tonight and report back.

[Kross]

FYI - Fuses were good but the fan relay appears to have moisture damage. Will replace and report back.

[DrFerry]

Originally Posted by Kross

FYI - Fuses were good but the fan relay appears to have moisture damage. Will replace and report back.

Find out where the water is coming from and fix it too...

[Kross]

Originally Posted by DrFerry

Find out where the water is coming from and fix it too...

Problem resolved. Replacing the relay fixed the fan. I found the source of the leak (door vapor barrier) and will be repairing that soon.

Much appreciated DrFerry

[RocketyMan]

Awesome! Thanks for reporting back your findings.