1.8 ohm Ballast

[Michael C]

I just installed a Crane XR700 in my 1970 280SEL. By all indication, and everything I have read, If I use my Bosch red coil, I need a 1.8 ohm Ballast resistor. I have found a 1.82 will that work / be ok? Having a hard time finding a 1.8, any ideas?

Michael

[Arthur Dalton]

That's close enough.
The best set-up for the XR700 is Bosch 0 221 119 030 coil [ Red] with 1.8 ohm (with a red band) MB part # 000 158 1745 [Bosch 0 227 901 014 ]

You can get them right here ..'68 280SE , pre transistor ign uses that combo.

[Michael C]

coil alone reads at .02 (Basically air/dirt)

[Arthur Dalton]

That's the right one

Here is the 1.8 ballast for that coil

http://catalog.peachparts.com/ShopByVehicle.epc?q=1968-Mercedes--Benz---80se--Base-Engine--Electrical&yearid=1968%40%401968&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=16097%3AMBC%7C10000017%3AED%7C10000082%3ASM%7C20%3AEB%7C1593%40%40280SE+Base&catid=240798%40%40Engine+Electrical&subcatid=240864@@Ballast+Resistor&mode=PA

[Arthur Dalton]

Originally Posted by Michael C

coil alone reads at .02 (Basically air/dirt)

Just the opposite....Basically close to a short circuit.
Which is why you need some more resistance [ 1.8 ] in the coil primary circuit.
A low R coil w/o Ballast would burn up the XR700 switching transistor b/c of high amp loading of a low R coil by itself.
You can still use Ballast By-pass for start b/c when cranking, the starter circuit draw drops the Bat + V to the coil, so you can still use that feature w/o fear of damage to switch-gear ..but once the car starts, you want Ballast.