Date registered: Sep 2012
Vehicle: 1972 Mercedes Benz 250
Location: Santa Fe, NM U.S.A.
Mentioned: 0 Post(s)
Quoted: 17 Post(s)
Need info on a ballast resistor
1972 250 /8 W114
So there are two ballast resistors right behind the battery (between the battery and firewall) I know that the 0.6 goes to the coil and I'm pretty sure
that there are no problems with that one, but the other resistor that is in there is a BERU WZ 04-2 0.4 and I would like to know if this is the correct one that is supposed to be installed in there and what is the purpose of this second resistor? If this is the correct ballast resistor, how can I test it to see that it is working correctly? Here is the issue that I am having. This second resistor has two wires on one side and one wire on the other side (I have not determined yet what these wires are for)
I was diagnosing why the horn wasnt working.
Here is what happened... The horn wouldn't work with the key NOT in the ignition, so I inserted the key and turned it to the second position (engine not running) and horn started working then after about a thirty seconds the horn wouldn't work anymore, I went to check fuse number 2 and noticed ALOT of heat coming from the two ballast resistors, I turned the key off and disconnected the negative battery terminal. I know theses resistors are supposed to get hot, but when I sprayed them with a water bottle the water sizzled right off like it would on a newly welded piece of steel. After several sprays of water to the point where the resistor wasn't sizzling anymore, I immediately connected the negative battery terminal, turned the key on to position 2 and tried the horn again and it worked. How can these be related? Also, I thought that the horn was supposed to work at all times (key not in ignition) Is my horn wiring all wrong? Is there a horn relay on this model? Also, is there a way to test the ballast resistor? Does it need to be tested under load? Any thoughts and ideas would be appreciated. Thanks!