[ysturrr]

HELP! Bought a 2011 335d with 62000 miles. Previous owner had a minor front end collision and was repaired. Only required front bumper replacement. Might be important, likely not. I drove it 200 miles home and noticed that the A/C blew warm at stops.

The electric radiator cooling fan never turned on. I noticed a small movement in the fan on startup with the A/C on MAX cool. I checked voltage across the cooling fan plug (vehicle side) and see 14.1V across the large ground and positive power terminals and getting between 4V and 10.7V across the ground and small signal terminal. I bought and installed a TYC fan from Rock Auto. It had some differences, i.e. the motor was more rectangular than the circular one I pulled out and there were no holes in the center of the fan to clip in the plastic A/C line, which the fan housing pushed toward the firewall, close to the crank shaft pulley. I ended using zip ties to pull the line back forward and fasten it to the frame of the fan housing.

On startup, the fan kicked on, slowly gaining speed and keeping the A/C cool while the car was stationary. I started prepping for an oil change. Heard the fan gaining speed, starting to whir as it should, and then five minutes later, nothing. It completely shut off. No movement. I checked voltage across the terminals again and had 12V across the large ground and positive and 10.7 on the small signal wire. Fan spins freely and no burning smell. No indication it is dead.

I found forum posts discussing the small signal wire often has poor continuity. This afternoon will chase the small signal wire and check continuity. I do not think this is the case but worth trying anything at this point.

Could this fan have died in 5 minutes?!?!? What to do? I need to make a trip to Florida (hot weather) on Sunday. Should I try to get an OEM fan from the dealership (ouch)?

[ysturrr]

Update,

I checked continuity of the small-gauge black-blue signal wire from the fuse box to the fan connector. Also checked quality of the wire. Continuity is perfect, insulation is intact and wire in great shape. Still getting 14V across Ground and Positive terminals and about 10.4V between ground and the signal wire. No fan movement on either two fans! HELP!

[Bavarian Tech]

Since you have a 335d, you have the upgraded fan (850watt) which is why your rock auto fan doenst fit right but anyways all bmw electric fans are PWM so a voltage meter is next to useless IMO, you have an external relay for the fan on the right side near the coolant tank. I would check that. Do you access to ISTA or INDA to do a fan activation ?

[ysturrr]

I do not have access to those programs. What should I look for at the external relay? I already checked voltage across the two large wires. Both give the same 14.1 volts I am seeing at the fan connection. From what I understand this is a fan disconnect relay and the fan typically has the constant 14.1 volts live at the connector, which is what I have. The relay looks great as well. Any other suggestions/tests I can do without those programs?

[ysturrr]

I also just used a wire to jump across the relay, effectively removing it from the circuit. This provided the same 14.1 volts to the fan primary power wires. Still no movement from fan. Will the 335D burn out the 600W fan? This seems to be what happened. I think I need to get the right 850W fan. Any good sources or any good ones for sale on here? Thanks for the input so far.

[ysturrr]

Did some more testing. I can't get continuity between ground and the large brown wire going to the fan connector. I figured this out when I took apart the 850W fan I have. The internals look great. When assembled, the motor spins freely and has the common steps you see in a good motor with magnetism. I hooked up the open fan to the connector which allowed me to check voltage entering the coil on the motor. The voltage was 10.1, likely not enough to spin the fan. I checked continuity on the internals of the motor. The coils are great and the cabling, positive, negative and signal cable, are all solid. When I tested continuity on the vehicle side positive cable, I had perfect continuity. When I tested continuity on the brown (Ground) cable, there was no continuity. Where does the brown cable go to ground? It meanders down into the firewall. Am I right to assume it grounds at the fuse box behind the glove compartment? If so, how do I access that ground point to tighten it/check it? I can't see it coming in behind the glove compartment and access is tight.

[ysturrr]

Chased the ground from the fan connector to under the air box. The nut on the bolt holding the brown ground wire was loose! When I installed the 600W fan from rock auto, I had to remove the air box. When I reinstalled the air box, I am certain at that point it was pushing down on the ground, making good contact, which is why the fan ran for the first five minutes. Then as the amperage increased, I bet I lost ground and the fan died! This is why I was having those symptoms! Before you ever buy parts, please check grounds and continuity on everything!

Thanks again for the help, so happy I can drive the 335d again!

[robnitro]

Thanks for the update. Yeah bad grounds are hard to diagnose if not under load!