cmacmillan
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Anyone know the secondary winding resistance on a 73-76 TR6 coil? The Bentley and Haynes manuals have the primary, but I can't find anything for secondary.
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secondary winding resistance?
- Thread starter cmacmillan
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cmacmillan
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Hmmm....I measured on the 20k setting on the multimeter and the reading was 6.5 (guessing that means 6,500 ohms). When I measured the primary, I couldn't get it to settle on a stable reading - it was jumping around quite a bit.
dklawson
Yoda
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martx-5 said:
Not necessarily. Though not really a transformer, coils sort of work like one in that it is the ratio of the number of low- to high-tension windings that determines the high-voltage output rating. So while the ratio of the number of turns could/should be off by a factor of 2 between a 1.5 and 3 Ohm coil, that could be achieved by changing the number of primary turns, not necessarily the secondary turns.
OP
cmacmillan
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Maybe I'll zoom out to the larger problem: it won't start!
-turns over fine
-checked fuel at the carbs and it's fine
-plugs, points, dist cap and wires are all about 5 years old, but I've done next to no driving, so they're close to new
-Was running well and then after 4 days of not starting it, I went to fire it up and nothing. Acts like it's trying to fire, but not getting there
-Pulled 3 plugs - light white sparks on 2, nothing on the other (I think 1 and 6 were sparking and 4 wasn't)
-held the coil wire to the block and got a small spark.
Is this sounding like the coil?
-turns over fine
-checked fuel at the carbs and it's fine
-plugs, points, dist cap and wires are all about 5 years old, but I've done next to no driving, so they're close to new
-Was running well and then after 4 days of not starting it, I went to fire it up and nothing. Acts like it's trying to fire, but not getting there
-Pulled 3 plugs - light white sparks on 2, nothing on the other (I think 1 and 6 were sparking and 4 wasn't)
-held the coil wire to the block and got a small spark.
Is this sounding like the coil?
TR3driver
Great Pumpkin - R.I.P
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I'd change the condenser and rotor first. Maybe also try running a temporary hot wire to the + terminal on the coil. Coils do sometimes fail, but are probably the most reliable component in the system.
In addition to Doug's comments, the secondary resistance also depends on the size and composition of the wire in the secondary; which has little or nothing to do with the voltage produced.
FWIW, I checked a newish Lucas DLB102 coil last night and got 8.8k on the secondary.
In addition to Doug's comments, the secondary resistance also depends on the size and composition of the wire in the secondary; which has little or nothing to do with the voltage produced.
FWIW, I checked a newish Lucas DLB102 coil last night and got 8.8k on the secondary.
OP
cmacmillan
Senior Member
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It's gotta be worth something!
Whoops - forgot to mention I did the rotor and condenser as well with the plugs/points/wires. Any chance any of those might have check out in a short time?
Whoops - forgot to mention I did the rotor and condenser as well with the plugs/points/wires. Any chance any of those might have check out in a short time?
Although most of my experience is with old motorcycles,not tr's,I have several with point ignition,and they often sit for long periods of time.I have found that a cleaning of the points contacts with a little sand paper or match pack striker even, and a blow of contact cleaner is almost always required.
Tom
Tom
TR3driver
Great Pumpkin - R.I.P
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Didn't we just have a thread on here about condensers failing early?
Anyway, yes, it is possible for almost any high voltage component to die early. 'Likely' is a different story, yet it's easy enough to swap in "known good" components (saved from the last tuneup) that I usually start there.
Side story: Friend of mine bought a new rotor for his TR4A at the 2000 VTR convention in Portland, OR. Less than 200 miles later, the car would not run at all. The rotor still looked brand new, no flaw visible, and yet another spare rotor got the engine started. That one would probably have failed quickly as well, but I insisted we also look for a bad plug wire. Turned out that the internal resistor in one of his plug boots was broken as well. The extra stress on the rotor (from the spark trying to jump the resistor) was what caused it to fail. I cut the wire and wrapped the end of it around the plug terminal (no boot) and he made it back to LA with no further problems.
Lots of sources warn against using sandpaper to clean the points, as it may leave scratches on the surface that promote more rapid burning in the future. I use a burnishing tool (designed for cleaning relay contacts), but in a pinch a bit of cardboard (like a matchbook cover) dampened with gasoline will do.
Anyway, yes, it is possible for almost any high voltage component to die early. 'Likely' is a different story, yet it's easy enough to swap in "known good" components (saved from the last tuneup) that I usually start there.
Side story: Friend of mine bought a new rotor for his TR4A at the 2000 VTR convention in Portland, OR. Less than 200 miles later, the car would not run at all. The rotor still looked brand new, no flaw visible, and yet another spare rotor got the engine started. That one would probably have failed quickly as well, but I insisted we also look for a bad plug wire. Turned out that the internal resistor in one of his plug boots was broken as well. The extra stress on the rotor (from the spark trying to jump the resistor) was what caused it to fail. I cut the wire and wrapped the end of it around the plug terminal (no boot) and he made it back to LA with no further problems.
Lots of sources warn against using sandpaper to clean the points, as it may leave scratches on the surface that promote more rapid burning in the future. I use a burnishing tool (designed for cleaning relay contacts), but in a pinch a bit of cardboard (like a matchbook cover) dampened with gasoline will do.
OP
cmacmillan
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Alright - I think I kept all the pieces I replaced, so I'll try to work my way back and sort this out.
I'm starting to understand the attraction of the electronic ignitions!
I'm starting to understand the attraction of the electronic ignitions!
OP
cmacmillan
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Nah - haven't...is this a good upgrade to consider?
TR3driver
Great Pumpkin - R.I.P
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Well ... there was a rash of bad rotors a few years back, and they were all black. As I see it, buying red rotors is kind of cheap insurance that you didn't get one of the bad ones.cmacmillan said:
Otherwise, I wouldn't say it was necessary, unless you have tried to upgrade other components for higher voltage (like using a Lucas Sports coil).