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Discussion Starter · #1 · (Edited)
I got a nasty surprise from my Mercedes GL450. Suddenly, my front and rear wipers stopped working while washer system is working fine. In addition, I started getting SRS error. Then, I also found out that cigarette lighter and glove box light has no power anymore. It seems like all started at once. I did some investigation and still cannot find the the issues.

1. The wiper switch brings rear wiper icon on the instrument cluster while I engage it. It seems like the combo switch is still working.
2. I checked wiper on/off and 1/2 relays and they seems to be working properly. However, the wiper on/off relay does not click while it is in the fuse box. It works well outside fuse box when I feed it even with 9v battery.
3. I checked the voltage on the lines to the wiper on/off relay and found out that lines 85 - 86 get 4.5-5.2v only. However the line 30 and 87 get 12.
3. I connected directly 30 and 87 and wipers started to work.
4. I checked the front SAM on all actuations available and all of them work solid, except wipers.
5. Removed the front fuse box and checked all of тhе connections. All of them аrе in a great state.

Now, I am lost and not sure what is causing the issue. I still cannot solve the problem. Wipers do not work. The only finding is that one of the lines is getting 5v instead 12v. I also do not see the relationship between SRS, cigarette lighter and glove box light.

I am wondering if anyone has the same issue and were able to solve it. Any advice is highly appreciated. Thank you!
 

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Discussion Starter · #2 · (Edited)
Still looking for the tips. Any help is highly appreciated.

Initially, I decided to replace the front SAM module to fix this issue since the only close pointer was to front SAM based on diagnostics with STAR. However, there was no a word about SRS error. Suddenly, everything started to work after a drive with a passenger on the front seat. I checked if the issues will come back with no passenger on the seat and it did, all issues got back. Then, I pushed hard on the front passenger seat cushion few times and error and all the issues gone. Now, I routed out the SAM as a problem.

Everything worked great for a couple of days and then it stopped working again. The first suspect was the seat sensors. Seat buckle seems to be working. At least, I don't see any unexpected errors on the dashboard. I removed the passenger seat out of the car and checked/cleaned everything there and was not able to find anything suspicious. Finally, I tested the weight system via STAR/DAS. All sensors communicate with STAR/DAS and provide the correct weight values. No issues reported. Now, I am sort of lost with this German engineered mystery. I just don't know what is the failure. I hope someone can help. Still looking for a clue. Thank you in advance.
 

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Discussion Starter · #3 ·
Not much help here, but I really want to help anyone who will struggle with the same issue.

I finally found what was the issue. It is all because of the faulty relay in rear SAM - (K) Circuit 15R relay with the part number Mercedes 002 542 2619. $10 part.

Ironically, the relay was working intermittently. As a result, I did much more work that I should be. I checked this part as the first step. During that time it worked. I hope it will save you a time and money.
 

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Discussion Starter · #5 ·
It took me a while to diagnose correctly because the relay was working intermitently. At the end, I needed to find out what unites all of these components by looking at electrical diagrams from WIS. It could be few other things involved, including front SAM. I replaced the relay and all issues gone. I believe this can be true for other Mercedes models because they share a lot in electrical design.
 

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Discussion Starter · #7 · (Edited)
It can be the issue with relays in the front fuse box. I believe one of them is relay# 101 on diagram but you should check for it. They were yellow in color on my car. There are 2 relays there, sitting next to each other, that are responsible for the wipers work. I would get all relays, including the one that affected my problem (relay with the part number Mercedes 002 542 2619) and replace them first. They are cheap and may fix the issue. Otherwise, it can be something else. I would start from here. Unfortunately, I did not do that myself and spent lot and lots of time and ended up replacing them anyway.
 

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Discussion Starter · #9 · (Edited)
The attached is the front fuse box diagram. The relays you need to look for are A & B. Part number I believe it is 1645402501 but you need to verify.

Regarding what fixed for me is what I stated above - "I finally found what was the issue. It is all because of the faulty relay in rear SAM - (K) Circuit 15R relay with the part number Mercedes 002 542 2619. $10 part."

The diagram for the load compartment fuse and relay box is also attached. You should look for relay 'K" on that diagram.
 

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Discussion Starter · #13 ·
You also need to check the relays from the from SAM under the hood. There are two relays that may affect wipers. I provided information for Mercedes x164 (GL450). Is that what you are working on?
 
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