S70Houston

Thought I would give it one last try to see if anyone has any further ideas here?

Drove it today and with the 6 speed manual, this car is super fun. But the keyfob not working correctly is getting annoying.

slammer111

Sounds like an antenna issue. Was the rear window ever replaced? The telltale sign is glass bits around that part of the car under the trim etc.

The fact that both keys stopped working sounds like there is a break in the circuitry somewhere.

I'd almost start poking around the electronics with a soldering iron.

S70Houston

Thanks.
The rear glass doesn't appear to have ever been changed, at least not by me. Everything worked when I purchased it for over a year.

Guess to the stealership she goes.

S70Houston

Thought of something here, .........

The car had a pretty bad tint job which bubbled, so I had the car re-tinted at a very reputable shop in the area.

As all worked before, and for sure worked after the tint job was redone, I hope that the rear window tint is not the issue?????

Thoughts.

Thanks Guys.

slammer111

I hate to break it to you, but I am 99% sure this is the cause of your problems. The liquid they use on the glass often flows into the electronics around the window and fries the antenna and related bits. This has happened to several coupes on this forum. It wouldn't take much for the same damage to happen on a sedan.

S70Houston

Thanks for the reply slammer.

A few questions:

If the electronics are on the top of the rear window, how could this happen, as the liquid due to gravity should naturally flow down, not up?

Does it take time for the liquid to find its way in there?

So I guess the electronics would need to be replaced? Are you aware of what the fix was on the coupes you mentioned?

I have had the same shop apply the same tint on my previously owned E320 and E350 (W211) as well as on a C300 (W204).

Are there differences, as there was never a problem with either one of them having this issue?

Thanks.

slammer111

My understanding for the coupes was that the tint people would often open the rear hatch before tinting, such that the water would flow towards the top of the window and short out the antenna. For the sedan I don't know where the antenna is located. Might be at the bottom of the window instead for example.

Some shops go use quite a bit of water, so who knows where some of it can splash and end up. But yes I would start poking around and see if something shorted out.

S70Houston

Thanks again.

Now with the hatch opened on a coupe, I can see it happening. On a sedan though, .......

My understanding is that the antenna on the sedan is on the top of the rear window under the headliner.

S70Houston

UPDATE - Car went to the dealership and was diagnosed with a bad antenna amplifier, which will need to be replaced.

bekkerh

Thanks for the explanation S70Houston, seems we have similar issues. I'm slightly confused as I have also read that the (amp) or other element is behind LHS c-pillar. Have you been able to sort your problem out. I guess my last step was to remove the window tint (although the previous owner mentioned it did work after the tint)
Car is going for a service tomorrow, will ask their thoughts aswell

S70Houston

Yes, a new antenna amplifier was installed, which solved my issue. I as well have window tint on my vehicle, which did/does not cause any issues. Good luck, keep us posted.

bekkerh

Thanks for the quick reply. Do you maybe have a part number for the amplifier? I'm guessing this is behind the roofliner? Which means the roofliner has to be removed or loosend?
Short of disconnecting the battery I have done all other checks that I could find
On Ebay I see a silver box or a flat black module
Black: A2038207989
Silver: A2038201785

S70Houston

Sorry, I do not. ​​​​​​​The dealer took care of everything for me.

S70Houston

I am SUPER disappointed!!!!!!

2 years ago the dealer replaced the Antenna Amplifier with a new one (I must assume OEM) and as of today, I am having the EXACT same issues with the remote not properly working as I did prior to replacing the Amplifier. Worked perfectly fine for nearly 2 years, no rear window was replaced, no tint work was done, nothing. Just not working anymore.

I have not checked the #8 fuse just yet, but again, all is EXACTLY as it was prior to taking the car to the dealer at the time.

Remote works while holding it close to the door handle sensor, Battery was replaced, red light is blinking on the remote, etc., etc.

Do parts seriously no longer last? I am sure the dealer will not warrant the part or the labor after 23 months, but come on,…………..

FRUSTRATED to say the least.

S70Houston

Decided to check out the car a bit more in detail today.

Turns out that Fuse #8 in the trunk is burned. Assuming this is the reason why the remote will no longer work properly. Went and got a new fuse, 7.5 AMP and it popped as soon as I inserted it in the #8 Fuse slot. Tried this a couple more times with a new fuse and every time, same result. Fuse pops as soon as it is inserted in the slot.

Now what could be the issue? Everything worked fine for nearly 2 years, what could cause the additional draw in the circuit for the fuse to pop? Defective Antenna Amplifier? (Which by the way believe it or not has a warranty on the part as well as labor for 2 years, so I am good as long as I bring the car in before November 02 (as confirmed by the dealer).

But, I would like to know what the issue here could be, otherwise the dealer will charge me if it is not related to the antenna amplifier.

Thanks for the help.

slammer111

Only way to diagnose is to see what fuse #8 is connected to, then start disconnecting things one at a time. Sounds like you got unlucky twice. Can definitely happen unfortunately.

Maybe try a wrecker for a used replacement part this time.

S70Houston

Thanks Slammer.

As stated below, parts and labor for the antenna amplifier from the dealer are good for 2 years/until Nov. 02, so I therefore would definitely not get a used part from a wrecking yard.

Therefore I guess the car will go back to the dealer to have it diagnosed.

Again, still wondering what could cause the issue if nothing was done to the car and why it worked flawlessly for almost 2 years?

Could disconnecting the battery possibly help reset what could cause the fuse to pop?

K3nD

I came across this thread by chance and read through all the comments. I also had this same exact issue that you're experiencing. Loss lock and unlock feature on both my key fobs while IR signal worked fine. After further investigation, I found moisture accumulation in the Antenna Amplifier around the rear windshield cause a recent rain storm when the car was parked outside. Dealer confirm Antenna Amplifier was defective. I suspect the rear windshield gasket/seal dry rot overtime letting moisture in. Now, fuse #8 never blew on mine, but blown fuse is mostly cause by bad ground. I wonder if moisture got into your amp and corroded some of the connections causing a bad ground. In that case, you might have to get a new amp and reseal your rear windshield.

Sadly, i never got to fix this issue on my prior to selling her.

- Previous Owner of a Mars Red C55

S70Houston

Many thanks for your input.

We had tons of rain in Northern CA this year, record braking as well as a LOT of snow in the High Sierra's. The car is parked outside ALL the time, so it is possible that water got in, absolutely. However, we had heavy rains early this year, why 6 months later does the problem all of a sudden appear? I would think that if water got in, it should have caused the issue already months ago? Now we had numerous days of over 100 degrees in the summer and most likely everything dried out again (if water gotten in), so why does the problem just now show up at the beginning of October?

Nevertheless, to my surprise the dealer stated that there is a 24-month warranty on the Antenna Amplifier as well as labor, so the car will go back next week Monday to hopefully address the issue. I would hope/think that when they replaced the part in 2021, they should have seen that the gasket on the window was bad and should have addressed that at the time as well to keep this from happening (Maybe once again wishful thinking on my part).

We shall see what the outcome will be.

S70Houston

UPDATE:

As mentioned, parts and labor for the Antenna Amplifier (installed by the local MB dealer in Nov. 2021) was good for 24 months, so the car went back to the dealer to rectify the situation.

Just got a call from the dealer informing me that the Antenna Amplifier is faulty and caused the issue, so another new one will get installed. I asked the dealer to verify that the rear window seal is ok and that there is no water coming in, possibly causing the issue.

I am however somewhat disappointed that an original OEM part does not even last 2 years before crapping out. And now, as the part is being replaced there is no more warranty, as it goes back to the original installation date (Go figure). Hopefully this time around it will not crap out again within 2 years.

S70Houston

I have to say that I sometimes truly question the logic of MB Dealers/MB's warranty policies???????

When I dropped the car off, I informed the service advisor that Fuse #8 is poping, and that they should check if it is indeed the Antenna Amplifier (AA) causing the bad circuit. Yesterday (as per below update) I am told that they needed to replace the AA as it was causing the issue.

Today's update is that the new AA did not solve the issue and that Fuse #8 is still poping, but after troubleshooting the circuit they found the Alarm Siren to be causing the issue????? SERIOUS?

- Now would one not troubleshoot the circuit first, PRIOR to getting a new AA?
- Did they just order a new AA, so MB would pay them for the warranty work?
- Now they are obviously getting some more money from me for the siren replacement.

So again, I am just puzzled, especially since the car was dropped off on Monday 10/23, and the new siren will not get to the dealer until this coming Monday, 10/30. I am without the car for a week by then, .......................

The worst of it all, my son is driving my ML550 to get to school and football practice, ........................... I want my car back.

KevinH2000

I had to replace the alarm in my car when I bought it. Apparently, it is a component with a high failure rate. I didn't have any of your symptoms.

I'm astounded that your dealership didn't follow up on your information about the fuse before replacing what I assume to be an expensive part. It was probably poor communication between the service advisor and the technician who did the work.

S70Houston

Poor Communication and a waste of money to say the least.

Another reason why I hate to go to the stealership, as I think they are incompetent in many ways, as this example proofs.

S70Houston

So the C320 is back, alarm siren has been disabled/bypassed as the part is on national backorder. Remote is working again as it should.

KevinH2000

I replaced my siren shortly after I bought my car 6 years ago. I don't know when it failed and how long I should expect the one I installed to survive. It will be interesting to find out whether the sirens become available again. I may need to bypass mine when it fails at some future date. I've read the component that causes the failure is a battery inside the siren. I think I saw a post showing how to dissect the siren and replace the battery with a generic one.

The siren is in the passenger-side front wheel well and the location exposes it to moisture. Mine was corroded and I didn't attempt to dissect it to see whether I could replace the battery. The next time I'm at the "pick and pull" I may grab one for possible future use.

I don't plan to visit my dealership service department for anything other than a recall. (I've had three recalls. One for the airbag and two for the sunroof.) I think they are primarily interested in warranty work and prefer to avoid working on older cars.