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car stuff - Mercedes AC

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#1

Wife drives a 21 glc300 - about 60k miles now. We had the "pleasure" of a 5.5 hour drive from SA to Houston yesterday (thanks a lot Seguin road construction) with no AC, and, possibly, heat running.

A buddy in Houston has a friend that is a mechanic (builds old muscle cars). He looked at it. he couldn't really diagnose the cause of the issue. His perception - the drain is not draining as well as it could. He said water was finding its way into the "case" and it was defniitely making some electrical components wet. He mention the various door/actuators not functioning as appropriate and pontificated that the water might have been causing the heater (allegedly located at the bottom of the "case") to kick on. Water was so voluminous that it was even finding its way to pad under the carpet on the passenger side.

He blew the drain line out, opened the "chest" vent actuators and told us that it should work fine on the way home if we left it set and running and didn't use "auto". Just set it on cool and adjust the fan speed.

About an hour into the ride home the same sounds and lack of air that ruined that lovely drive to Houston reappeared. The fan began making a high pitched sound and it felt like the heat was on. Air flow out of the vents felt VERY restricted (like 10% of what it was). I was literally about to drive the car into the concrete and call it a day.

On a lark I turned off the compressor. For about 3-4 minutes the air was "cool" and the fan was blowing "normal" and hard. then it started blowing "normal" but warm, which is what I expected. I turned the compressor back on and it worked again like it should.

I talked with the mechanic hoping the new data would help him diagnose. He offered some educated guesses, but it doesn't seem like anything more than that. It's very possible that one of the components got wet and sending faulty signals to the module for the ac system causing the actuators to change modes from ac to heat at the blend door actuator and or mode door. Is it blowing out the defrosted or floor vents. Also if you have a chance to stop look under the passenger front door area near the transmission. That's where the drain should be dropping water.

Anyone here ever dealt with this? I am uploading two photos he took and here is what he told me. "Water coming out of the hole in the larger hole in the first picture. Also out of the vent that goes to the lower passenger dash panel. Water is coming out of several areas. Also draining on the floor under the carpet from ac case. I blew out the drain hose. There may be something inside the case not allowing it to drain properly. "

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#2

my mercedes was totaled a month ago. It was a good car, but I didn't dare work on it myself. My truck AC goes out and I'm all over it. Mercedes shit is too complicated for the average Joe.

  • Author
#3

Not looking to fix it myself. Just trying to get as knowledges possible before the tech tells me I need a whole new car because domaflitchy is flushed.

#4

I've owned 2 Mercedes. First never let "a guy that builds old muscle cars" touch anything. Go to "a guy that works on foreign shit everyday."

  • Author
#5

sure. I agree in concept. The vehicle isn’t going to be repaired by muscle car man. His observations about where water is located and where it should be located seem pretty universal. The Hope was someone else had similar issues and could help diagnose the problem.

my in laws had aGLE that had similar issues. Theirs presented a tad different with cool air coming out of the drivers side only. Very low air flow. 4 “fixes” by the dealer and issues persisted. They sold the car and moved on. I’m hoping to avoid the need for multiple repairs and a month or more without my wife’s car.

#7
1 hour ago, UTPhil2006 said:

I Feel like @blacklab had or had a Mercedes and a specific mechanic

He recommended Ben's Workshop on Congress when I needed a Mercedes PPI, and I was pleased with the quality of their inspection and report.

  • Author
#8

Too bad thats in Austin and I am in San Antonio. I do appreciate the recommendation, though. I took the time to consult AI this morning and have some additional theories to process through. They are logical. It starts with evaporator core freezing - restricting air flow. This could explain why it progressed from "Working" to not and then back to working after running it without the compressor for 5-10 minutes.

The question would then be why? Low refrigerant? Possible. Water not draining? Possible. Given the observations of the mechanic, the drain issue gave him the most concern as a concept because of the amount of water it was producing to locations that are not ideal for water (including lots of electronics). Maybe there is something blocking the the line inside the case.

In any event - I think I have enough data to talk semi intelligently with a tech that is trying to convince me that its fubar.

I am still open to ideas if anyone is more experienced than me - and chat GPT.

#9

Heights Auto Haus is great with Mercedes. 1407 N. Shepherd.

once my e-class was out of warranty, I took it there for everything. Until I found myself there every other month with constant new problems.

one time I dropped my car as they were closing for the day. The owner gave me a ride to my house. In his pickup. I couldn't help but ask why he didn't drive a mercedes, or other german car. He only laughed and said that he only fixed them, he didn't want to own one.

Edited by Nice Guy Eddie

#11

I am sure there is a Mercedes forum somewhere that would be a good place to ask these questions (not that there is anything wrong with asking here). I follow a couple 4Runner groups and they are good places to seek info on issues.

#12

The Mercedes dealership out just north of 410 on San Pedro is great. Why wouldn’t you just take it there for a diagnosis?

#13

A while back my e63 was having some electrical problems and the place I usually went to couldn't figure it out and told me to take it to the dealer. I took it to Mercedes Benz of Austin and they ended up spending over 100 hours trying to figure it out and never solved the problem. I bought a used instrument cluster off ebay and they put it in as they had to put it back together anyway and were able to get it running. Total charge: $100 diagnostic fee.

  • Author
#14

closing the loop - evaporator core had a "crack" and leaked. Replaced under warranty (really) and we are back up and running.

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