Climate Controls Went Dead

[shark88]

So, I'm working out of town this week and the wife calls me Monday evening saying she was on the local freeway (doing 65+) when a car in front of her came to a complete stop. She slammed on the brakes so hard the abs kicked in. She didn't get hit or hit the stopped moron in front of her. She did say the a/c went off and the climate control panel was dead. So I get home today and start pulling fuses. A/C fuse #48 was blown. I replaced it and everything seems fine. I'm just concerned about how the sudden braking coincidently blows that 7.5 amp fuse. Any ideas? It's a 2002 model w/aftermarket Pioneer radio installed by p.o. We've owned it for about 2 months now. I'm wondering if maybe the climate control wiring plug(s?)may have been bumped/knocked loose when the stereo was installed? Any other ideas?

[shark88]

So, to follow up a bit, the wife gets in it today and as soon as she cranks it up the controls go dead and no a/c. When I got home I pulled the blown #48 fuse, pulled the glove box completely out, inspected the wires from the unit routed by the dash brace which had the cover on the sharp edge to prevent wire chaffing. I cranked it up and wiggled the harness and everything worked fine. Put it all back together and pulled out the controls and saw nothing suspicious. Tonight I've read about cleaning the temp sensor slots, checking wiring on the drivers side, and fan motor resistors. Apparently, the e39 controls are not compatible. The E53 controls are very pricey even used so I'm going to be disassembling and cleaning some stuff next.

[SlackTube]

I would need to look at a diagram but if that's a power fuse for the IHKA control unit than anything from a bad compressor to a faulty AUC sensor can cause that fuse to blow. I would try TURNING OFF the snowflake button and see if the fuse is ok for a few days. If the fuse does not blow then press the snowflake. If the fuse then blows you need an A/C compressor.

[shark88]

Here's what I wound up doing today:
1. Drove it about 12 miles this morning and as I pulled out of the neighborhood it popped #48 so I pulled over and quickly replaced it and went on to get the oil for it's oil change. As I drove I turned the compressor off & on and tried other functions too as SlackTube mentioned but couldn't it to blow #48 again.
2. After the oil change I pulled the control module out off the dash. I noticed the left side vent temp sensor slots were full of dust. The little fan visible on the backside of the controls was also dusty. I saw evidence of where the PO possibly spilled a drink as well in the right side slots even though these are not open like the left side slots. I used my spray contact cleaner to clean the fan and the slots. I also gave the control buttons and the rear fan controls a shot or two. I put everything together and drove it another 10 or so miles giving all the buttons a workout even turned the heat on for awhile. I noticed the buttons feel more precise when pressed so that may help confirm the spilled drink theory. So far so good.....
3. Looking at the Bentley, there sure is a lot of inputs and outputs for this control module!!

[shark88]

So, I hop in yesterday morning after working on it the day before, crank it up and it pops the #48 fuse right away. One thing that popped in my head was the auxiliary electric fan kicks on in both my e46 and e90 when the a/c is on. I didn't notice this on the X5 even after driving it for awhile. I've been driving it on short trips this weekend turning the A/C off before switching the engine off. Then once I crank it I wait a few minutes to turn the A/C on. No popped #48 fuse so far......

The Bentley says when it's first started the ecm activates the auxiliary electric fan briefly at 20% speed then shuts it off. This is for diagnostic monitoring of the fan. It supposedly generates a voltage as it coasts down and the ecm matches it against the previous data.

So, I raised the hood and watched the auxillary fan as my daughter cranked it with the snowflake button off. The fan didn't move a bit. I left it running and had her turn on the snowflake (A/C) and it bumped once, stopped, bumped again, stopped then finally spun up to normal speed (Sure is quiet to compared to the E90 which sounds like it's going to taxi down the runway!) Anyway, we did this a few times each time the fan bumped once or twice before full speed. Is this normal?

[itsbrokeagain]

I believe it does the bump as a self-test to see if the fan will work, if not it will store a code in the system. So it's normal operation as you have described.

My aux fan is shot and I can still use the AC, but only on the highway as the forced air cools the condenser. In stop and go traffic the high side pressure reaches 400psi and it shuts the system off...

Need to get to fixing that as the hot weather is here...

[shark88]

I believe it does the bump as a self-test to see if the fan will work, if not it will store a code in the system. So it's normal operation as you have described.

My aux fan is shot and I can still use the AC, but only on the highway as the forced air cools the condenser. In stop and go traffic the high side pressure reaches 400psi and it shuts the system off...

Need to get to fixing that as the hot weather is here...

Thanks Itsbrokeagain!
I have discovered the self bump test is true. Why would BMW do this and I wonder if it contributes to aux fan failures?