plonkster
New member
I replaced the final stage driver this morning. Reason: The blower fan will turn off after 10 to 15 minutes. The only way to stop it from doing this is to put it on the fastest setting when you start the car. Obviously the unit heats up and stops working, but a higher setting (ie less resistance) means less heat. More on this later.
Some thoughts, notes, advice follows.
First, you can find a very nice howto here: http://www.motormec.co.uk/aircon.pdf
Some advice and details:
On the 320d e46 there are a few differences. The OBD2 plug is there, but the warning buzzer and footwell light isn't. Less wires to disconnect.
The so called sharp metal clips really just clicks into place, as long as you work carefully there isn't any real danger of damage.
The ventilation pipe down there got in the way the whole time, but you can work around it. Having a head mounted flashlight might help, but I didn't have one.
Some people (on other forums) had trouble with their T-20 driver being too long. I have one of these socket-set kits with a 1/4 inch ratchet and connectors so you can use the torx bits with the ratchet and an extension. This worked really well.
Pull fuses 28 and 50 while working on this. Keep the unit plugged in while pulling it from its mounting point, the plug gives you better grip. I didn't do this and used long-nosed pliers instead, and it was a real pain to get it out of there. BMW has helpfully over-engineered the fitting (two screws and two plastic clips) while under-engineering the part itself causing it to fail every couple years.
When I finally got the old part out, I saw it was manufactured in the 29th week of 2005 (ie it has already been replaced once before, also indicated by screwdriver scratch marks and a missing screw), and the part number differed slightly. That means BMW changed the part again since 2005, and the old one lasted 3 to 4 years. Hopefully the new one will last longer. Then again, I might just sell the car before then.
Some thoughts on that. It seems the final stage resistor unit is more than just resistors. Looks like all the parts that generate some heat was mounted in this package, and it consists of a couple resistors and transistors. From my limited analogue electronics knowledge (ie not switch mode), the slower you want the fan to go, the more heat is dissipated in the transistor/resistor setup. In other words, this unit relies on airflow to cool it down, but when there is the least airflow, this unit generates the most heat. One would hope that the engineers factored that into the design, but I suspect this is a case of an initial design flaw, which led to the mounting space being made just that big, which now means you have to make the replacements just that big... the obvious improvement where the "hedgehog" now have more prongs has already happened.
In addition, it seems this part is also used in the X3, the X5, some M5's, Rovers, Land Rovers and Range Rovers.
I'd be interested to hear of similar experiences and/or thoughts.
Some thoughts, notes, advice follows.
First, you can find a very nice howto here: http://www.motormec.co.uk/aircon.pdf
Some advice and details:
On the 320d e46 there are a few differences. The OBD2 plug is there, but the warning buzzer and footwell light isn't. Less wires to disconnect.
The so called sharp metal clips really just clicks into place, as long as you work carefully there isn't any real danger of damage.
The ventilation pipe down there got in the way the whole time, but you can work around it. Having a head mounted flashlight might help, but I didn't have one.
Some people (on other forums) had trouble with their T-20 driver being too long. I have one of these socket-set kits with a 1/4 inch ratchet and connectors so you can use the torx bits with the ratchet and an extension. This worked really well.
Pull fuses 28 and 50 while working on this. Keep the unit plugged in while pulling it from its mounting point, the plug gives you better grip. I didn't do this and used long-nosed pliers instead, and it was a real pain to get it out of there. BMW has helpfully over-engineered the fitting (two screws and two plastic clips) while under-engineering the part itself causing it to fail every couple years.
When I finally got the old part out, I saw it was manufactured in the 29th week of 2005 (ie it has already been replaced once before, also indicated by screwdriver scratch marks and a missing screw), and the part number differed slightly. That means BMW changed the part again since 2005, and the old one lasted 3 to 4 years. Hopefully the new one will last longer. Then again, I might just sell the car before then.
Some thoughts on that. It seems the final stage resistor unit is more than just resistors. Looks like all the parts that generate some heat was mounted in this package, and it consists of a couple resistors and transistors. From my limited analogue electronics knowledge (ie not switch mode), the slower you want the fan to go, the more heat is dissipated in the transistor/resistor setup. In other words, this unit relies on airflow to cool it down, but when there is the least airflow, this unit generates the most heat. One would hope that the engineers factored that into the design, but I suspect this is a case of an initial design flaw, which led to the mounting space being made just that big, which now means you have to make the replacements just that big... the obvious improvement where the "hedgehog" now have more prongs has already happened.
In addition, it seems this part is also used in the X3, the X5, some M5's, Rovers, Land Rovers and Range Rovers.
I'd be interested to hear of similar experiences and/or thoughts.
