If I had a manual I would not be asking ......

On older American cars I always associated these with the iginition system.

The car did not run at all today, installed a new battery and a while later these two units were hot to the touch.

Is that normal?

Attached Thumbnails

 

they look like inline resistors to me so, yes they would be hot to the touch when in use. they are used to reduce voltage and the energy is dissapated in the form of heat.

you don't say which car they belong to so hard to say what they do, but its quite likely one is to govern the low speed function of the auxiliary fan. if you've got two fans, then you've probably got two resistors.

__________________
1987 300e manual 250,000 km (sold)

Thanks Simmo!

auxiliary fan?.....NOPE! it's a 1978 250 from Germany...not a grey sales...brought over by the owner in 84.

I was messing with some minor electrical and the key was on at times.

Got alot done taday!


The dash lights were easy!.....The rheostat needed to be cleaned up then re installed....no biggie.

After going to three mercedes and two Euro junk yards NO BLOWER MOTOR to be found ( no real surprise there ) so a 1992 Chev Cavalier blower and fan fit right in! no problems....I just used three self taping scrwews and mad proper connections and WHOOSH! new blower! works just fine. ( did not think about the amp difference utill now ) hmmmm.....gonna have to keep an eye on that one heck it was already in my garage collecting dust and one spider

Hi,

These are ballast resistors used to reduce votage to the coil to about 9 volts for normal running.
When you crank the engine to start they are by-passed to give direct battery voltage to the coil and improve starting performance and once the engine fires the ignition feed to the Ballast Resitors takes over.
I would suggest you post this question on the Vintage Mercedes forum where there are a lot of people with much more knowledge than me on this. Or maybe do a search there under Ballast Resistor.
I have the exact same resistors on my 1975 Merc 350se W116 and was able to find all sorts of helpful info here.

On my model I believe one is 0.4 ohms and the other is 0.6 ohms which you can measure.

Hope this helps.

Vincent.

Thank you!

Ignition ballast resistors.
The .6 is coil dropping resistor and the .4 is switch gear dropping resistor.
Both will disipate heat with ignition sw ON.
Normal

Thank you Arthur!