C5 X7 Heater Blower Motor Fault finding - no fan spin

[C5x7dude]

Hi hope someone can't point me in the right direction for fault finding a none spinning blower fan.

Fan spins up when removed and put across a 12v battery.

Speed control module has been swapped for a known working unit - have also tried bridging the connector block with it disconnected.

Relay under bonnet seems ok - both wires coming out read 12v with engine running.

Fuses seem good.

Control panel seems to work - i can select from zero to full speed.

Voltage at fan is reading 2.5V with car running and any fan speed selected from low to high but fan does not turn.

Any thoughts before I freeze to death would be most welcome.


Thanks

[wurlycorner]

Have you checked the earth from the fan connector is ok?

[C5x7dude]

Have you checked the earth from the fan connector is ok?

Good shout I'll double check this - pretty sure i checked and had continuity to ground but best be sure.

[C5x7dude]

Done a little more

From fan control module connecter with module disconnected >

• Pin 1 - earth - good continuity to chassis ground.
  Pin 3 - to motor - good continuity to motor connector
  Pin 4 - good continuity to motor connector and also reading battery voltage with engine running.

With module disconnected and pin 1 and 3 jumped and blower motor disconnected >

• motor connector good continuity to chassis ground
  battery voltage 13v+ at blower motor connector when car running

With module removed and pin 1-3 jumped and motor connected - nothing, motor go no spin.

Tried another blower motor out of a working car - still no joy.

fettled the motors by spinning them with pins jumped and car running, no resistance so don't think they're stalled.


So next question - is the relay within the fuse box under the bonnet accessible / serviceable? I've swapped out fuse 11 again for a new one.

Feels like once it sees a load across the motor it pulls the voltage down - given the earth side is good I can only think high resistance at the relay, else I'm stumped.

[wurlycorner]

Grounds can test good on continuity, but be unable to carry current.
Probably ok, but to be absolutely sure, try a temporary direct ground to the motor and see if it works then, or try using the motor ground to light a high current test bulb (eg headlamp).

[C5x7dude]

No dice, tried taking the motor direct to chassis ground.

Tempted to wire in a relay next as the fuse box seems potted and inaccessible.

[C5x7dude]

Solved

Loom from motor splits via a connector that had overheated and melted. Carries the supply and return to earth.

Good shout on continuity not equaling a solid connection. Earth was good but supply not so much.

Makes sense why I could read supply voltage at motor but when a load was seen it dropped due to high resistance at this crapped out connector.