What the heck is this cracked part

[akessel56]

See image:

On the drivers side of engine compartment behind headlight is a ceramic (broken) thing - that could be a resistor of some sort.

See image - this is on a 280 sl (71)

Its busted, don't know what it is, what it does, and if I should replace it.

Thanks for any help!

Andy

[Lars G]

Check this link http://www.sl113.org/wiki/Electrical/TransistorIgnition
I think it the ballast resistor to the ignition system. I suppose you have one red and  white also?
Br
Lars

[49er]

 A ballest resistor it is. Surprised the car would run with it cracked.

john

[69280sl]

A ballest resistor it is. Surprised the car would run with it cracked.

john

I don't think the ignition system is too sensitive to the resistor. My car didn't have any when I first got it. Car ran ok, but the lack probably wasn't doing the points any good.

Gus

[akessel56]

We'll, so this would make some sense, as on a longish trip the car died and I needed to replace the points.

That said, there are two of these..

One connects directly to ignition coil and the back end of that connects to this resistor.

There is also another wire I haven't traced that connects to it along with the wire that comes to the resistor by the ignition coil.

The other end seems to head back I assume toward the firewall.

Anybody have an idea of a part to replace it with?

[akessel56]

okay so looking at that picture, this ought to be the top resistor, the .6 ohm one

[akessel56]

Excuse me the .4 Ohn resistor.

[ja17]

Sounds like someone may have by-passed your factory electronic ignition.  Does the small primary wire from your distributor go to the coil or a terminal block? 

[akessel56]

It looks like this is the proper configuration, though I can't tell for sure without unhooking everything.
On wire from the .4 ohm Ballast resistor is heading through the firewall - presumably to the ignition switch as it should.
The two wires then comming out of the .4 ohm balast resitstor each go in a separate direction (I would say the right directions) but are getting bundled with other wires so not certain of their destination, but heading in the correct general direction.
So I assume its good.

Ordered a new .4 ohm resistor and we will see.

I tried measuring it with an ohm meter, but couldn't get any reading, the connectors are too coroded.

Makes me think about replacing the .6 ohm one, which otherwise looks fine.

Reading the article on these, it certainly would seem, that damage could be done to the points if this isn't working properly.

I presume its got at least a completed circuit or it looks like the car wouldn't run at all given that the ignition module won't have any power it would seem.

[ja17]

Where does the small primary wire from the distributor go?  Also, if the transistorized ignition is still hooked-up, one wire on the coil will go directly to ground (earth).

[akessel56]

the small primary wire to distributor?  which one is that?  the one that is really small and internal goes to the condenser contraption.

I never noticed any other wires except the ones that go to the plugs and the ignition coil.

Andy

[ja17]

There is a small wire coming out the side of the distributor from the points and condensor. It is may be green color. If it goes to the ignition coil, your electronic box is by-passed. Cars like yours with factory electronic ignition should have this wire running to a two post  terminal block, then onto the electronic box under the battery.

[garymand]

Its good to see you have the battery disconnected.  It looks like the porcelain was hit and broken or the screw was over torqued and the twisting broke the porcelain housing.  I see a fresh break with no charring from overheating the resistance eliment.  The resistor may be still in resistance specification, still connected electrically, and only physically compromised.  That said, was it broken before the points were replaced?  Is it possible someone over tightened the terminal in an attempt to make sure all the connections were snug, and broke the porcelain housing?  

It’s built to dissipate a lot of heat without the housing damage.  Typically these resistors only open from heat cycling fatigue or accidental breakage.   They are in series with the coil primary so they don’t normally see the full 13V to ground.  They are there to limit heating the coil by reducing the current through the coil and whatever is switching the primary on and off.

I’m surprised you can’t get a resistance reading.  That may mean it is actually open as well as the housing broken.  Without the housing holding the resistance wire between the terminals, its not too hard to break the resistance wire.  But without the resistance, your coil would not get current either at starting or while running depending on which resistor that one is.

[akessel56]

thanks well i replace it, took some effort to undue the screws.
I think its been cracked for a long time.  Don't know.
I'm hoping this may have been the ultimate cause of my issues which began with a 7 hour car ride and the car began misbehaving (sputtering) about 3 hours into it and finally stalled when pulling to a stop and would restart for several hours.

Then when it would restart it was running poorly until I replaced the points, but still wondered what caused the issue.

I would think with the coil not tight, it was seeing less resistance and i'm hoping it was the higher voltage damaging the points.

Time will tell, need to take it out on the road for a stretch and see if it starts to act up again.

Everything else seemed good, the car sounds and feels good at the moment.

I also replaced the condenser, while I was at it.

Thanks all, I will let you all know how it goes.

[akessel56]

The only wire coming out of the distributor goes to the little black dohickie circled in the photo below.
It has a lug at the top that connects to that wire inside of the distributor.
ultimately the wire goes under the battery.