348 348 tb interior blower fan only works intermittently

Some of these types of intermittent/vibration-induced problems can be traced to the wiring harness connector on the back of the display/HVAC unit.

There have been several examples mentioned on the forum, but I can’t find the right search words.

Since any wire can be affected, not just the power wires, I imagine that the display may be ok during these failures.

Are you getting any fault codes?

 

Harness connection or faulty solder joints. My guess? Solder joints. Deteach the frontal unit and check for continuity of them and clean connectors. This unit is fragile....and rare.

 

I have a spare in the original box.

 

I mean this:
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Did you try the diagnostic test?

 

Mine gets stuck on. I tracked it to a wire behind the console. I’ll rely on a friend to fix it for me as electrical isn’t my strong suit.


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Well, I was only suggesting a common cause of intermittent HVAC issues. With extra information such as you have provided, it opens up new possibilities.

Does the fan stick when you rotate it, whilst pushing axially? (Or is access limited for you to try this?)

Fans do wear out and put extra load on the fan speed controller. Controllers often fail as a consequence, but I think the controllers are more commonly known to work, then stop working completely, not just stop when going over bumps or around corners.

 

Mine just pulls right out. I’ve got to lift the top at an angle around the lip then it pulls out. Maybe mine is broken but it’s really easy to do.


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I've been talking with m.stojanovic about fan control speed, and he is a massive help. This is some info he send me yesterday. He can also make new fan speed regulators if the ECU is sending the correct codes.

m.stojanovic, Yesterday at 3:02 AMNEW
1. The Fan Speed Controller - If you unplug only the small connector from the Controller, does the fan run at ignition "on" or not?
If the fan does not run with the small connector unplugged from it, you can test it as shown on the drawings below.

Keep the large connector plugged in, unplug the small connector. Connect a length of wire to Pin 6 and bring +12V from somewhere with another wire. Strip about 6mm of insulation from each wire. Switch the ignition "on" and, keeping the two wires at ~5mm distance and ensuring that they do not touch each other, squeeze them lightly with your slightly moist fingers. If the controller is good, the fan will start running at varying speeds depending on how hard you squeeze the wires.

Alternatively, you can use a 5V supply with a potentiometer as shown below:

Or you can use a power supply which can vary voltage from zero up, negative to chassis, positive to Pin 6.
If the fan runs at varied speeds when tested as described, the Controller is good.