Diagnosing power antenna problems + unknown device - PeachParts Mercedes-Benz Forum

#1 04-22-2007, 01:57 PM

I just took the antenna out of my '81 240d and if this isn't "German Engineering" I don't know what is! Judging by the weight I think it's actually bulletproof ...

Anyone have a wiring diagram and/or suggestions for diagnosing why it's not working? My multitester & I are ready for this afternoon's job but don't know where to start .... I got as far as checking the fuse.

Also, what's the second device in the trunk mounted next to the power antenna? It has a long bar sticking through it ... and I have no idea what it's for

.

Thanks!
Steve

justinperkins · #2 04-22-2007, 02:00 PM

This might help you... Hirschmann Not Working? Or is it?

It's for a newer-style antenna, but still could be of some help. What problems are you experiencing?

I don't know what that other device is, but looks vacuum-related.

300SD81 · #3 04-22-2007, 02:01 PM

I'm pretty sure thats the sunroof motor.

No diagram, but the first thing to test is to try jumping the motor to power, then there are some little contacts that sense where it is in its rotation, try separating or shorting some of them. Use very thin wire when trying to short them, so if there is a short circuit, your wire melts instead of the ones in the antenna.

#4 04-22-2007, 02:02 PM

The other thing is the motor for the sunroof.

#5 04-22-2007, 02:09 PM

Thanks for the quick replies! Afternoon now fully booked

Thanks again;
sga

JimmyL · #6 04-22-2007, 03:20 PM

Quote:

Originally Posted by daleearl

Thanks for the quick replies! Afternoon now fully booked

Thanks again;
sga

This is kind of funny, because this is how I spent yesterday afternoon....
First let me say that in the past I've had a car that had a bad switch in the dash that was causing antenna problems.
That was not my case yesterday, though. The Squash antenna wouldn't go all the way down, it would stop about a foot short.
To make a long story kind of short, the motor worked fine if I ran 12vdc straight to it {thank you battery booster and alligator clips}

Just reverse which motor wire the clips are on to change direction.
So it was something in that relay/actuator/wheel assembly, and I have no idea what. I just swapped the mast to another unit I had that I think was from this car originally. The one I swapped out was from the '77 that is now gone.
It is interesting to see how these things work. I still have no idea how they shut themselves off after the mast is raised/lowered. I see how the wheel lifts up a contact to remove voltage, but there are sooo many other things in there!

I never knew where the inner "tail" went, but it is pulled through and into a round bobbin type thing.
And yes, over-engineered......

Jeremy5848 · #7 04-22-2007, 07:35 PM

Quote:

Originally Posted by JimmyL

...It is interesting to see how these things work. I still have no idea how they shut themselves off after the mast is raised/lowered. I see how the wheel lifts up a contact to remove voltage, but there are sooo many other things in there!...

When I had the one on my wife's 87 apart, I could find no limit switches to stop the travel. The circuitry seems to sense the increase in current drawn by the motor as it stalls when the antenna reaches "full up" or "full down." That has an additional safety advantage in that, if the antenna hangs up on something, gets broken off, or simply jams due to dirt, the motor won't continue to run until it fries, causes a fire, or drains your battery. That is proper engineering.

Quote:

Originally Posted by JimmyL

...And yes, over-engineered......

No such thing. Proper engineering means that the Hirschmann antenna can be taken apart and repaired. Proper engineering makes for more expensive manufacturing, however, so often the engineers are told to "make it cheap" rather than "make it good." There are ways to engineer something better and less expensive -- ICs, which replaced transistors, which replaced vacuum tubes, for example, but too often it's just a manager trying to reduce his budget.

Jeremy

#8 04-22-2007, 08:02 PM

Jimmyl: Same experience here ... works fine off the direct 12v dc but hook to the wiring harness & it only goes one direction, but most importantly, the "reverse direction now" relay doesn't work.

It's clear the motor works but either the dash switches are bad or the relay is bad. I read full current at the device but only in one polarity ... does that mean the relay is bad? Without a proper pinout it's hard to tell but I'm guessing that's the case.

More as this saga unfolds ... at the moment, the mast is up and my s.o. is happy about it so it's time for a beer

.

sga

300SD81 · #9 04-22-2007, 08:55 PM

The antenna uses a switch to stop, lemme see if I can explain it.. Borrowing a pic since I don't know where I put my broken one. Part C is an adjustable arm thingy that makes part B turn about 45 degrees for every full rotation of the pulley that the antenna cable wraps around. If you look closely at the top of part B in the pic, there is 1 pin on the gear thats different from the rest. That one goes between the switches (A). So the full travel of the antenna is a full rotation of B, or 8 rotations of the pulley. If the motor is good, you might want to check A for bad connections. I don't think there are any relays in the antenna. It took me about 20 minutes to fix the junkyard antenna I pulled with the part B from mine after I broke the mast, and swap the tubes that the antenna goes into. Mine had a lot of internal corrosion so I didn't just swap the mast.

Any chance theres a market for rebuilding these things? I could make a few bucks..

vstech · #10 12-28-2010, 03:31 PM

ok, i'm bringing this thread to the front for someone looking to fix his.

newtodiesel · #11 01-03-2011, 04:00 PM

OK ALL I am a her not a him...

Thanks for digging this up John...read thru most of the info
I knew for certain the mast was obviously broken...reinstalled a new one per the instructions here...disassembled the box for the antenna, poked around finally got out the circuit board and looked at the back..it was all black..made a guess that it was bad
replaced the board with a new JY find..and wha la...my antenna works!!!! WOOOOHOOOO.....thanks for all the great info...I love this place!!