OT Do we have any factory Mercedes Technicians here, GLK Blower Motor/Resistor Issue Options

[seanery]

Hi guys, I have a 2012 GLK with 36,000 miles on it. The car is in great shape. Recently, I've had issues with the AC/Heat blower motor. It started to work intermittently, then stopped altogether. I read a bit online and see that is a common problem with Mercedes. The issue coming down to blower motor failure or resistor failure.

I bought a new blower motor, but before I installed it, I plugged it into the resistor in the car and it was a no go. So I ordered a resistor and had it overnighted. It showed up this morning, I tested it with the old fan, plugged both in, turned the car on and the fan worked. I packed it all up, put the bits back together and turned the car on, and no go. Right back to where I was before.

I tested the voltage coming TO the resistor and get 14.7-14.9V. I test both units outputs and get .7V. Obviously not enough to drive a van. The thing that gets me is that it did work for my 30 second test.

As for wires that go to Resistor:
1. Power
2. Common
3. Yellow wire? Sensor? I'm not sure what this does

Wires from the Resistor:
1. Power to fan connector
2. Common to fan connector

The fan control powers up, and I can hear things change when I change modes, etc...The car makes AC and heat, just doesn't blow it.

I'm in a huge timecrunch and this is baffling me! And BEHR is such a big, machine that getting a hold of someone there has proven fruitless.

Any help? Ideas?

TIA!

[isdyl]

Hi - I'm not a Mercedes Tech but have had a similar issue on a BMW with the heater fan controller resistor. They call it the 'heater hedgehog'. I first replaced the resistor and it worked intermittently. After a while of fiddling I noticed that the after market resistor had slightly smaller pins that the OEM, and even the OEM from BMW had smaller pins (I went to the dealership and looked at it).
The whole problem had been caused by the actual fan bearings failing which had caused one connector pin on the resistor to overheat and melt leaving a bad connection.
I replaced the fan (quite a big dash-out job), and fixed the resistor plug and has been fine ever since.
I would suspect your fan is ok as its a relatively young car, so have a good look at the resistor plug.
Dylan

[seanery]

Luckily for me, they are relatively easy to get to. I wish my problem were as solveable as yours proved to be. I had to slide small paperclips into the factory harness to get my meter reading on them - my meter's probes were too large. Even the tiny paperclips made a good connection, and I'd be terribly surprised if both resistors and both fans had the same problem. If I put voltage to the fans, they bot spin.