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samuelsantana
Samba Member
Joined: February 11, 2010
Posts: 4
Location: orlando,fl
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 Posted: Thu Aug 25, 2011 6:29 pm Post subject: Engine and coil problems |
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Hey guys, I am having a bit of a problem with my recently rebuilt 1641cc motor.  when I leave the car the car on idle for like 20 minutes (hatch open) the coil will heat up more than normal and then the motor will start to heat up also. I have replaced the coil 3 times with new and original ones and they do the same thing. What I am wondering is if these 2 problems are connected. The motor was also placed in the correct timing position with a timing light. Any help is appreciated thank you. |
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Bikerchris
Samba Member
Joined: May 08, 2010
Posts: 290
Location: Texas
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| Posted: Thu Aug 25, 2011 7:20 pm Post subject: |
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| I had a problem similar to this once and it seems to me it turned out to be the wiring in the ignition switch. Does that sound logical to you? |
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RailBoy
Samba Member
Joined: March 10, 2008
Posts: 2904
Location: Virginia
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| Posted: Thu Aug 25, 2011 7:27 pm Post subject: |
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| Resistor....????? RB |
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lostinbaja
Samba Member
Joined: December 19, 2004
Posts: 4036
Location: Frankfort, Illinois
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| Posted: Thu Aug 25, 2011 7:31 pm Post subject: |
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Some coils have an internal resistor and some require external resistors. A coil spec'd for a 12v VW will have an internal resistor. I take it you have a 12v system?
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RailBoy
Samba Member
Joined: March 10, 2008
Posts: 2904
Location: Virginia
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| Posted: Thu Aug 25, 2011 8:18 pm Post subject: |
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| Not so sure about that, have seen motors with 12 Volt & Resistors mounted to the fan shrouds, they looked stock..... But it was a while ago, could have been 6 volt systems though..... RB |
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samuelsantana
Samba Member
Joined: February 11, 2010
Posts: 4
Location: orlando,fl
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| Posted: Fri Aug 26, 2011 3:17 am Post subject: |
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| Yes its a 12v system and as far as I know the coil has a built in resistor. We thought it was a resistor problem but all 3 of my coils got hot. I don't think I have 3 bad coils. This motor is in a 1966 bus and before I purchased it, it was converted to 12v from 6 volt. Also when I rebuilt the motor I changed the generator to an alternator. Thanks guys |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26787
Location: Colorado Springs
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| Posted: Fri Aug 26, 2011 3:34 am Post subject: |
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The coil should have a resistance of 3-4 ohms for points or the usual modules. Across the 12V and points lugs.
The resistance is the main thing that determines how much power they draw. |
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RockCrusher
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Joined: August 03, 2010
Posts: 4596
Location: Parkesburg, PA
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| Posted: Fri Aug 26, 2011 3:52 am Post subject: |
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| modok wrote: |
The coil should have a resistance of 3-4 ohms for points or the usual modules. Across the 12V and points lugs.
The resistance is the main thing that determines how much power they draw. |
You're up mighty early today! E=IR or I(4amps)=E(12volts)/R(3ohms).
Don't let the 4 amps scare you coz it's intermittent current and peak at that. The inrush current is 4 amps and decreases as the magnetic field builds and the total time is 50* x 2 per engine revolution of 360* so the heat rise should be less than the equivalent of 1 amp at 3 ohms full time....more like .25 amp heat. Of course the faster the engine turns the higher the average current.
RC
EDIT-I said that backwards (I see, now that I'm awake) The resistance is high at the beginning and lessens as the with time so the current gets higher with time on each cycle BUT as cycle frequency increases with RPM the inductance shows increasing impedance so the current becomes less and less with increasing RPM. That's why the output voltage starts to drop off over the coils RPM limit in typical ignition systems.
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Last edited by RockCrusher on Fri Aug 26, 2011 8:28 am; edited 2 times in total |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26787
Location: Colorado Springs
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| Posted: Fri Aug 26, 2011 4:07 am Post subject: |
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| Oh crap, I forgot to sleep |
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samuelsantana
Samba Member
Joined: February 11, 2010
Posts: 4
Location: orlando,fl
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| Posted: Fri Aug 26, 2011 4:46 am Post subject: |
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please help, I'm loosing sleep over these.  |
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modok
Samba Member
Joined: October 30, 2009
Posts: 26787
Location: Colorado Springs
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| Posted: Fri Aug 26, 2011 4:38 pm Post subject: |
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man, this morning was rough
Anyway, if the points have somewhere near the right gap and dwell, and the coil has the correct resistance, and it's hooked up right, and you tried three coils, then it must be ok.
right? |
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