I'm ordering a new mast for my antenna, which was broken when I got the car. Can I bench-test the antenna unit with 12 Vdc to see if it actually runs before I reinstall it? There are six pins which connect it to the harness; I reasoned I could apply power to one pin and ground one, and it will run if it is OK other than the broken mast; seeing the circuit board, though, I dare not experiment lest I make things worse, so I need advice on which pins to use if this is possible. Thanks.

just connect it in the trunk off to the side and be sure the mast doesn't hit something, use a helper if needed, better safe than sorry so you don't burn up the internal electronics in the motor.

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1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins

You could take the cover off and locate the 2 wires attached to the motor. 12V from a source should safely make the motor turn. You are downstream of the circuit board, so this shouldn't cause any problems...

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1986 560SL
2002 Toyota Camry
1993 Lexus

Ok, both good ideas, thanks.

good idea to test the motor, but if the electronics are fried, it will not show up

__________________
1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins

OK, guys, I got my new mast (thanks, Phil!), put my antenna together, installed it in the car, and it would not run in either direction. So, I pulled it out, tested an antenna salvaged from a 300E, and it ran, so I got the broken mast out of it and swapped the guts from it into the housing of mine (mostly so it would have the correct 126 part number, but of course the mast for the 124 is too short). I installed it in the car, got the motor running the right direction, and fed the mast in, and it sucked it right in, but stopped when it got to the point it should have pulled the last section of the mast into the car. I loosened the nut, gave it a little push, and it sucked it the rest of the way in. Now I can't get the switch to extend it; when rocking the switch on the dash I can hear it make a little bump like it is trying, but it won't extend it. Can anyone offer advice as to what is wrong?
Thanks, again.
EGAD: thought I'd better disconnect the harness, because of electrical unknowns. I left Barrett-Jackson, went into the trunk, grabbed the harness connector, and HOT!. I got it unplugged, removed the antenna assembly, and back to the kitchen table. Popped the cover off, and the circuit board was hot, but not burned that I could tell. I thumbed the sprocket on the motor drive and the antenna extends and retracts very smoothly and easily. Something is obviously wrong, though. Comparing the internals of both units, they appear to be identical.

Didn't win the bidding on the Duesenberg, eh? Oh well LOL.... OK, I think you have 1 or both circuit boards bad, very common on old Hirschmanns, or the dash switch is bad, or you have a wiring issue.. IMO, the dash switch is a useless feature, and as you know, only works properly with the circuit board to vary the height of the mast, hence my descriptor 'useless'.
If you do a search, there is tons of info on troubleshooting this issue. It may simply be a wrong wire from the antenna to the harness. I think there are several circuit diagrams in the archives too. Try testing a different dash switch, they do go bad.
I once swapped out the internals from a cheapo antenna to get the unit to work like a 'normal' aftermarket, with all the advantages of the quality in the motor and gears, none of the dash switch/circuit board hassles...but that's not likely what you want.

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1986 560SL
2002 Toyota Camry
1993 Lexus

I agree it's probably the circuit board or the switch. I noticed that, as soon as i plugged the harness to it, it started running. Turning the radio on and off and operating the switch did not seem to make any difference. I'll get a switch and see if that helps; 'course I might have fried the circuit board. Oh, well...

This site has wiring diagrams for various newer Hirschmanns. Perhaps one of them might help to sort out the pins. http://products.hirschmann.de//index.php?sessiontoken=20071013195317-11111111&manid=4&CFID=&CFTOKEN=&pbparam=tid=980,pid=776,spid=2,maid=26,view=2
look at the 'pin seizure' pdf's.
I'm adding a pin-out diagram, if it helps

Attached Thumbnails

 

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1986 560SL
2002 Toyota Camry
1993 Lexus