So the AC in my GL450 has worked great, no real issues. Couple weeks ago, the light on the left temp wheel started blinking and I noted the air coming out was not as cool as the right vent. I don’t drive it much so no worries, but last week the AC began to get a bit wiggy, blowing hot, not blowing, etc. seemed ok if I turned the temp to low and manually adjusted the fan. Well I got out the iCarSoft and found the left center vent temp sensor reporting a short along with historic LIN bus communication errors from numerous flap motors as well as LIN voltage not within valid range. Disconnected the sensor, now shows open circuit and LIN errors returned. Bought a new sensor, fixed that issue, but the AC blower is not blowing and the LIN bus communication errors return when reset. Blower test shows proper position of control switch and changes when the switch is adjusted, but no voltage at the motor. Looking at things like the evaporator temp and compressor, it seems the system is operating but the blower is not getting juice. I suspect the answer lies in the last code; 960A LIN bus error tips: BUS communication not possible.

Questions
1: is the control unit for the ac system integrated into the control panel on the dash?
2: does the control unit supply voltage to the blower, or where is the voltage sourced?
3: is there a way to reset the unit?
4: Where is the mysterious LIN Bus?
Any suggestions?

 

I have “woken up” and googled the LIN bus and true, many articles exist. Most highly technical and way above my pay grade as an ambitious DIY’r, the others, stories of guys ripping out dashboards, testing or replacing component after component to the same end. Ironically, most of those posts are on this very forum. So I checked into the MB WIS subscription, 60 bucks a day? I have looked into it before and have yet to find the “free” access mentioned elsewhere on this site. I did order a copy off eBay, so waiting for that to arrive.

I thought the purpose of this forum is for MB fans to help one another with problems that would otherwise be impossible or costly to fix. I am certain there is a fault, my guess is the control unit as a result of the shorted sensor. No doubt in my mind there is nothing wrong with the 9 stepper motors showing a fault. If there is a physical device called a LIN bus, I would most certainly like to lay eyes on it to see if there are any physical issues.

so if anyone has any helpful insight, I would be very grateful

 

LIN bus - never heard of it.
You can get WIS with a cloned DAS system for about 800 bucks.

Has it rained much where you are, and is your car parked outside?

 

Yes, I have found the WIS for premium pricing as noted. My hope is others have experienced similar issues and resolved it without spending $800 to diagnose a $12 sensor. Or perhaps a seasoned tech might have experienced this chain of events and offer a suggestion.

Yes, I am in Florida and it has rained a lot, the well on the passenger side is dry as i check it regularly. the sunroof drains were clogged when I bought the car and there was some evidence of water in the past, (never seen any actual wetness) but none since I cleaned the drains months ago.

 

Reason I'm asking for rain is that if your ac drains are clogged; rain or condensation can pool in the ac vent system - you can hear it sloshing around in turns (with ac and radio off).

I've had the sloshing noise from time to time when parking outside and not driving the car for prolonged periods during the wet season, but I've also never had wet floors. With radio on, sometimes my left or right speaker would cut out.

Trapped water may in your case account for the intermittent short circuit and voltage/communication issues you're seeing.

I put the car in Sauna mode and never had any more issues.

 

Blower diagram and where and how does it get power including the climatic control fuse

 

Thats a great suggestion but i know for certain the drains are working properly as I thought the drip on the floor mat might have been the AC, therefore, i checked them when i cleared the sunroof drain. Thanks for the tip!

 

Thanks antiguangenius that is exactly what i needed. I will pull the control and ensure i have power there before proceeding further

 

no problem...

I have attached the whole pdf before I was on the go so did screenshot from my phone but here is the complete system info, hope it helps

 

check your cabin air filter box ASAP if you haven’t already.

 

Excellent. I see exactly how it works and will be out there with my meter tomorrow checking it out. Bet I just have a blown fuse under the seat...
Thanks again antiguangenius!

 

Cabin filter is clean and dry,, just replaced it.

 

michaelm352 l have exactly the same symptoms. Did you solve your problem?
I have power on both sides of fuse #91 but no power input to blower motor. Ground at 29/2 is good.
Power to automatic climate control is good. Ground is good. I have LIN bus errors 9601, 9604 and 960A. I disconnected battery negative terminal and reconnected after 5 mins. Now giving me terminal 30 error but l suspect this will reset. Any more ideas?

 

I got out there this weekend with the meter and started testing via the wiring diagrams. I found in have voltage at the fuse under the seat, At the blower fuse on the right end of the dash and at the blower motor its self. I also found the voltages coming from the control unit to the blower resistor to be consistent. So i ;pulled the blower to have a look, it shows evidence of water intrusion on the controller and bench testing, the blower will not run at all. That all said, I ordered a blower with controller off ebay today and will see what happens when i install it.
There are two different connectors at the blower, one is only two wires and should show voltage at all times. the other connector is the inputs from the climate control system and the voltage will vary on each of these wires.
hope that helps!

 

WIS is $60-70 for a 24-hour subscription ... which of course is less than any professional hourly rate and consequently a bargain.

 

Thanks, I found a copy on ebay and picked it up. Works like a champ and gave me all the info i need to trace and test the system.

 

I am not an electrical engineer, but best I can figure out is the system had codes on the actuator motors and blower all stating "LIN Bus voltage not within valid range". In checking the blower, there was power on the main power wires, so looking at the electrical diagrams, It appears the blower control throws a voltage related signal to the actuator motors to determine what they are supposed to do, probably based on a varying voltage or perhaps a varying ground from the main system control. Despite the lack of any diagnostic codes for the blower control, it was indeed the cause of the actuator motor and LIN bus codes. A new blower with controller fixed it all!

 

So to finalize this one, I discovered yet another well in the floor I was unaware of. I found this after the car sat for about 4 months while I recovered from open-heart surgery. I'm in Florida so yep, it rained. When I went to start the GL, no go, nada, nobody home. After pulling things apart, removing seats and carpets I found the well on the left side flooded, literally full of water. only one that was dry was the battery hold. The left side had six inches or so. Called State Farm, bought me out of the car and spent the money on a 14 Explorer Sport Ecoboost. Water ingress seems to be the root cause of all the aforementioned bizarity.

 

Yep