Quick help with distributor brush

ghostdancing

True Classic
Just purchased new cap and brush fitted them but motore refuses to start
I tested The brush : there Is no continuity From inside contact and upper arm. .what is wrong?
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Update: just realized that the inside piece of metal is just a spring, not an electric contact but I got no continuity (tried also on 20 k ohm range. In the picture it's The new rotorbrush. Is this part fault or I am wrong?
 

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Some rotors (brush) have a resistor inside. It is inline between the two contacts. The resistor can burn out, or in this case possibly be defective. That prevents continuity from traveling through the rotor/brush. Sounds like you got a bad one, perhaps contact the seller for an exchange or buy another one.
 
thank you Jeff, that's why i also tried on the 20kohm tester range (if i recall correctly this resistor it's 2-3kohm).. but have to say that my old rotor (we call it spazzola, brush in italian) shows near zero resistance measured from center contact to the edge (as in my pictures)..so probably the new part it's a bad one..
 
thank you Jeff, that's why i also tried on the 20kohm tester range (if i recall correctly this resistor it's 2-3kohm).. but have to say that my old rotor (we call it spazzola, brush in italian) shows near zero resistance measured from center contact to the edge (as in my pictures)..so probably the new part it's a bad one..
The rotor resistor is there for EMI suppression. Usually in the 5K Ohm range. If you want all out performance and don't care about noise in your radio, you could solder a jumper across it.
 
The old one (with zero resistance) likely does not have a resistor in it. Not all of the "spazzola's" do (that would make a great nickname for someone). Like he said above, it is for noise suppression and not all applications need that.

In theory, having resistance in the ignition secondary (high tension) circuit can actually increase the spark potential, provided the coil has enough energy output to overcome it. Sort of a spin off of Ohm's law. But for reliability sake I would prefer one without it. These resistors tend to be a trouble area. I guess the constant high energy "zapping" that goes through it causes a short life span. Same with the rotors (spaz's) that have a RPM limiter built in. They cut out the spark at a specified RPM, but tend to fail resulting in no spark (same as your faulty spaz).
 
The old one (with zero resistance) likely does not have a resistor in it. Not all of the "spazzola's" do (that would make a great nickname for someone). Like he said above, it is for noise suppression and not all applications need that.

In theory, having resistance in the ignition secondary (high tension) circuit can actually increase the spark potential, provided the coil has enough energy output to overcome it. Sort of a spin off of Ohm's law. But for reliability sake I would prefer one without it. These resistors tend to be a trouble area. I guess the constant high energy "zapping" that goes through it causes a short life span. Same with the rotors (spaz's) that have a RPM limiter built in. They cut out the spark at a specified RPM, but tend to fail resulting in no spark (same as your faulty spaz).
Since the resistor is in series with the spark plug, I'm not sure how it could enhance the spark, especially since the coil secondary is a relatively low output impedance. That is the reason many performance apps use either copper core (Do they still make Packard 440?) or helically wound copper core (if you still want to hear AM radio). The typical factory wires use carbon composition core (or at least they did a few years back) and are in the several thousand ohm range. They tend to go up in resistance a fair amount as they get old. I'm still using the helically wound copper wires I bought in the 70s and when I measured them a few months ago, they were still in the couple hundred Ohm range. They were sold by a relatively new company at the time called MSD. I think it stood for Magnetic Suppression Discharge in their marketing literature.

I can't remember if my X originally had a resistor rotor but I'm sure it came with resistor wires. My memory is a little fuzzy on whether or not any cars used both, but as I recall most American cars used resistor wires and non-resistor rotors. I wonder if they are just making resistor rotors now because the volume is low and they wanted to cover their bases. They may have been designed for cars with solid core wires originally.
 
that's interesting; i hear that copper core spark plug leads are not ok with electronic ignitions and capacity discharge units (that boxes that works with original points)..looks like that EI must "feel" some resistance otherwise they get broken easily..is this correct?
 
that's interesting; i hear that copper core spark plug leads are not ok with electronic ignitions and capacity discharge units (that boxes that works with original points)..looks like that EI must "feel" some resistance otherwise they get broken easily..is this correct?
The capacitive discharge units I have installed recommended using them.
 
talking about CD units, have you experience with the US MSD products? i mean that one that produces multiple sparks...
 
how it ended? i had another NOS rotor,measured the resistance and it was infinite (no continuity), tried in the car: no start..then had a third and it shows 10Kohm resistance: with this rotor the car started this morning.. so looks like an old (but new, nevers used) rotor can became fault in says 30 years of shelf stocking.. really i cannot figure how can a resistor get broken (infinity resistance) by simply rest in a box, but this was the experience i made
 
10K resistance sounds right, they come in different values for various applications, so this rotor should be good.
I agee, most likely both bad rotors were bad when you got them. By chance did you buy them at the same time/from the same source? Not that it's the case here, but there has been a major problem with counterfeit parts in the automotive industry. And unfortunately Bosch has been one of the targets for them; high demand and higher profit potential.
Regardless, the important thing is now you know everything is good with your engine and it starts. In the future, I would try to get spazzolas (love that word) that don't have the resistor. Although they often don't specify it, so that might not be easy to know. For what it's worth, there are MANY applications that use the same basic model of Bosch distributor (assuming your's is a Bosch). Lot's of car makers used it for many years, and the basic parts are interchangeable (for the most part). So you can get rotors for all sorts of non-Fiat applications that will fit properly. As a result, parts suppliers often sell them indiscriminately, which is why some may have resistors inside while others don't. The vast interchange of applications also means you can find the same part for less cost under a different listing (funny how the specific vehicle may demand more for the identical item - look for Fiat parts listed for Ferraris to get an example).
 
unfortunatelly the original marelli part (no resistor) it's no longer available, the part that can be bought now it's made by FACET, an italian aftermarket company that makes electric related automotive parts; the 2 fault NOS spazzolas that i sourced locally where made by other brands (dont remember them, where old worn carton boxes)..anyway i found a FEMSA electronic unit @ 150,00 eu and eventually will buy it to get clear of the old marelli S135 + cheap CD box that i currently run
 
N.O.S. - "Non-working Old Stock" returned to retailer by original customer some 30 years ago for a refund, then resold in a large lot of inventory during a bankruptcy sale 25 years ago. I just bought an NOS horn button the other day that had two tabs instead of three. It had 30 years of dust in the fracture of the missing tab and had gone unnoticed the whole time.o_O
 
how it ended? i had another NOS rotor,measured the resistance and it was infinite (no continuity), tried in the car: no start..then had a third and it shows 10Kohm resistance: with this rotor the car started this morning.. so looks like an old (but new, nevers used) rotor can became fault in says 30 years of shelf stocking.. really i cannot figure how can a resistor get broken (infinity resistance) by simply rest in a box, but this was the experience i made
The resistor rotors I have seen have some sort of encapsulant over the resistor. I would not be surprised if the failure had something to do with the temperature cycling of the encapsulated resistor. That was an issue the entire electronics industry was coming to grips with in that time period. I've got a couple old ones I should take a look at and see if they are still good. The one I am using at the moment is 5K ohms. You should be able to solder a jumper wire across it if you want to reclaim the bad rotors.
 
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