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Long post alert. Grab a tall glass of coffee before reading.
2002 ML320 with the modernized climate control system.
My AC quit working on me a few months ago. Took it to my mechanic who hooked up a code reader & among other errors he could see an "AC compressor" error code.
So, he changed the AC compressor and recharged the gas, but no AC
He recommended I take it to an electrical expert who sent 12V through the compressor line directly (back of the AAC panel) and the compressor clicked on, but the AAC panel would not send 12v.
So, the electrical expert suggested that I get a new AAC panel, which I did from Ebay.
New AAC panel wouldn't turn on the AC either - so I gave up for the time being.
Electrical guy took screenshots of the error codes & gave them to me (attached to this post)
Come winter, I notice no heat either! I just chalked it down to a bad AC panel and chugged along
Then, came across a thread on this forum I think which said that a bad auxiliary water pump could cause the AAC panel to get fried + no heating.
Then it clicked to my thick skull that it was one of the errors that was on my photos from the electrical guy (B1108)
Checked my engine compartment & found that my aux water pump was sitting on top of the engine manifold! Don't know how it got there - maybe mechanic disconnected it from its mount on the side of the battery compartment and left it there!?!
The connector on the bottom of the aux water pump had burned out, and possibly shorted.
So bought a new EGR valve connector pigtail (it is the same one used for the aux water pump as well) & soldered it to the wires i.e. white to positive & brown to ground
The old aux water pump refused to come on.
Checked voltage on the new connector soldered on point #12 and only noticed 9.2V and 0.2A on the connector (something seems off) - this was when the AAC panel was set to full blast past 28C (Canadian variant)
I have a new aux water pump as well, but haven't changed out the old pump coz I now need inputs from the experts on the forum.
What are your views guys?
The gas levels in the AC system etc. are fine and no issues - confirmed by both mechanic & electrical guy.
Going by the above, I think at point #4 & #5 the electrical guy connected the new AAC panel as well and possibly fried that too?
Now, while doing point #12 I've added an inline 5V fuse to the aux water pump line so the problem doesn't occur again i.e frying the AAC panel inadvertently.
I'm worried about point #14 since I'm not getting 12V on that line anymore!
I needed inputs from the experts here and thought I'd check with you guys before ordering any new parts/doing any more work on her.
Do you think another new AAC panel should fix the issue? Or is there something more sinister going on here?
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