1989 300E weird problems!!!!

[300ESUPER]

My 1989 300E has a few problems. My first problem is when the car is off my factory alarm goes on (as the siren sounds very loud) for no reason at all. I have no idea why this happens.

The second problem I have is, yesterday I left a small but full perrier bottle of water in the car near the radio and since it went below freezing last night the bottle exploaded in the car and when the weather became warmer the frozen water became unfrozen. Now my radio does not work, the on/off power button on the radio lights up but nothing happens when I try to turn the radio on and I also noticed that on the display of the radio I noticed which looks like symbols frozen in place. But the weird thing is after this all happened I left it for a while and an hour later I noticed the alarm was going crazy and the antenna was going up and down making a grinding noise all by its' self. The car was off during this little episode. I check the fuse of the radio and the fuse was fine. I have no idea what it going on.

I think I need to replace the radio. If I do how do I take the factory radio out and how would I start to diagnose all these weird problems?

Thanks,

Fab

[ARNOLDLewis]

The problem could be anything from a too-sensitive shock sensor, to an electrical fault in the vehicle which is tripping the alarm, to a defective alarm unit itself. Best idea would be to take it to a pro and have it checked out.

[tinypanzer]

There are a couple of other simpler possibilities as well. It could be a door switch or a hood or trunk switch. The factory alarm is set to go off if any door, the trunk or hood is opened while the system is armed. So, if you have a switch that is flaking out, or isn't lined up as well as it used to be then that could be your problem.

Check the one under your hood first. On an S-class (not sure about your car) it is mounted to the firewall using two screws. I could see those getting loose and making the switch sag. You could put a small o-ring around the shaft of the switch and slide it all the way to the base. Then, when you close the hood the o-ring will slide up the shaft as far as the switch went in. This will tell you how far the switch is actually getting pushed in. The same trick will work on the doors too.

Worth a check....


-tp

[tinypanzer]

Man, it's so friggin' weird that you posted this problem the other day, because now I'm having the same issue.


Check this out - driving through downtown Tallahassee after the big FSU-Florida game, in the middle of heavy traffic.

BlannHH BlannHH BlannHH BlannHH BlannHH My alarm starts going off as I'm driving down the road!!

So I pull over. Stop the engine, play with the ignition key. BlannHH BlannHH BlannHH BlannHH BlannHH no response. It keeps going off. I get out and look around. I am becoming a spectacle.

I put the key in the driver's door, BlannHH BlannHH BlannHH BlannHH BlannHH. So now I'm getting pretty pissed off. Finally, it stops. The heatlights keep flashing. I think it's finally over. Ten more seconds elapse then BlannHH BlannHH BlannHH BlannHH BlannHH BlannHH again. It won't stop. I frantically open the hood to look for the horn. It's not the regular horn, no siree it's hidden behind under the windshield wiper cover.

So, it stops again. I go to get my tools out of the trunk and as soon as I open the trunk BlannHH BlannHH BlannHH BlannHH BlannHH BlannHH BlannHH it starts all over again. I grab a tiny little crescent wrench out of my tool kit and go to work on the battery terminal. It loosens finally and I pull it off.

Silence.

Ahh, but what to do now? I'm in the middle of a sidestreet and so far I'm not blocking any traffic. So I figure I'll just wait for a second and re-connect the battery and hope that a good reboot will make the car happy.

I cross my fingers and reconnect the terminal.

.


.


BlannHH BlannHH BlannHH BlannHH BlannHH BlannHH BlannHH BlannHH BlannHH BlannHH


Curses!

So I pop it back off again. By now a guy who was driving by to help has stopped to see if he can be of assistance. Of course he couldn't because how does one fix a spastic MB alarm system in the middle of the street?

One doesn't.

Finally, I admit defeat. I give the guy $5 for stopping and bid him farewell. Now I must suck it up and drive my car back home and get my trusty '78 Volare so I can continue on to the gig.

I reconnect the battery. So far so good. I close the hood. BlannHH BlannHH BlannHH BlannHH BlannHH . Oh well. Time to roll. I get in and start the car after putting my tools away. I drive two miles back to my house in rain and traffic sounding like the polezei the whole way (with 30 second breaks in between).

I park the car in my drive waBlannHH BlannHH BlannHH y and jump out and disconnect the BlannHH BlannHH BlannHH battery.

Sigh.


Time to go to work and leave this nightmare for Sunday.



Let's talk......

[J.HIDALGO]

They usually fail. Just disconnect it...if that does not work, disconnect the actual alarm brain under the carpet in the front passenger area. Do a search...

[300holst]

When I got my '86 300e the alarm horn under the hood had been disconnected. The only alarm indication was the flashing headlights. This worked ok in dry southern California. When I brought the car home to moist Oregon, the alarm started going off at random. Since my wife was a bit shy about driving with the headlights flashing, I just went under the passenger carpet and disconnected the alarm module. There was some moisture under there and I understand that the alarm module is sensitive to moisture.

As far as your radio is concerned, I think moisture has gotten into the control board. Maybe it will dry out eventually but in the meantime I'd suggest disconnecting the antenna with the antenna raised. Then you can avoid the up-down action and can check to see when or if the radio dries out. You might try a hair dryer (carefully) to warm up the face of the radio. I don't think Perrier water contains any sugar. If it does, the radio could be beyond any easy repair.

[tinypanzer]

Well, after poking around in WIS, I located the infamous 'N26' box and it was indeed under the floor panel on the passenger's side.

I pulled it out, and problem solved.


Well, not really. I just had to crack the box open and see if I could figure out what was going on inside.

At first, it looks fairly complex, but it really isn't. The whole system is armed or disarmed by the state of a latching relay (it's the silver one marked Siemens).

I figure that since my alarm went off when I was driving, a condition that should never happen when the system is disarmed, the problem must be either in this relay, or the circuit that switches it on and off. So I pulled it off the circuit board. After testing with a 9v battery, I verified that the relay was in fact switching as it was supposed to. So, the problem must be in the circuit that switches it on and off.

What I am going to do to test this:


1) Solder 6 long wires in place of where the relay was.
2) Put the box back in the car
3) Arm/disarm the system and use a meter to verify that the control voltages to the relay are correct and adequate.

After this, I will hopefully know a little more about what actually failed. We were undergoing some VERY wet weather at the time, but the alarm box was bone dry, and the whole circuit board was varnished so not as succeptable to moisture as some would think.

The only thing that makes any sense short of the alarm itself failing is moisture getting in a door switch that arms/disarms the system.

I'll let you know what I find. I think this is repairable.


-tp