How hot does your coil get?

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luftvagon
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Location: Little Rock, AR
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How hot does your coil get?

Post by luftvagon » Wed Apr 17, 2013 7:45 pm

How hot does your ignition coil get? I don't remember my coil getting very hot in stock L-Jetronic form triggered by distributor with points. Now I am sporting Pertronix, and different ECU/pickup.
It's hot to the touch in just xx minutes of idling. How cool is that? No pun intended.
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

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RSorak 71Westy
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Re: How hot does your coil get?

Post by RSorak 71Westy » Wed Apr 17, 2013 8:22 pm

It's getting too much voltage. Usually a coil only receives full batt voltage during cranking, then after the engine starts, the coil is fed a reduced voltage around 9 volts. The Ballast resistor does this job. This is how most cars work, I think VW's are different.
Most VW coils if I remember correctly have this resistor built in to them. If so I dont see how it can be bypassed or i.e. how you can even feed too much voltage too it ?
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

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SlowLane
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Re: How hot does your coil get?

Post by SlowLane » Wed Apr 17, 2013 10:29 pm

First of all, I think it's normal for coils to run warmer than what would be comfortable to hold for any length of time.

Rick is correct, our VW's don't use external ballast resistors like 'Merican cars do ( or rather, did). Instead, the VW coil incorporates an internal ballast resistance (typically 3 ohms). So no, there is no way to provide "full voltage" to the coil during cranking. The ballast resistance is a permanent, inseperable part of the coil.

Luft, check your dwell with the Pertronix. I was shocked to discover that the dwell provided by my cherished Crane XR700 system was running at 71 degrees. I can't say one way or the other whether it made the coil run warmer or not because of this, and frankly I didn't much care: the XR700 worked flawlessly for the 13 years I had it in the van. But if you're really that curious, measure the temperature of your coil with Pertronix, then swap back to points and measure the coil temperature again.

Or better yet, convert to a direct-fire EDIS system that your mega-micro-maxi-squirter system supports. :geek: Ya know ya wanna.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"Wisdom comes from experience. Experience is often a result of lack of wisdom."
- Terry Pratchett

luftvagon
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Re: How hot does your coil get?

Post by luftvagon » Thu Apr 18, 2013 5:47 am

It's coming!
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

DugB
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Re: How hot does your coil get?

Post by DugB » Fri Sep 14, 2018 6:41 am

Very timely to find this thread, as I was just wondering the same thing. My '75 bus, running well with a Camper Special 2.0 (stock FI setup for '75), seems to have a warm coil, too. I checked it with an infrared thermometer after my 7 mile commute on local roads this morning and it came in at 130 degrees F. I do have 10V at the coil...I had thought that was an issue but after some of the previous comments in this topic I'm thinking that's normal.

- Doug :-)

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Amskeptic
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Re: How hot does your coil get?

Post by Amskeptic » Fri Sep 14, 2018 8:00 am

DugB wrote:
Fri Sep 14, 2018 6:41 am
Very timely to find this thread, as I was just wondering the same thing. My '75 bus, running well with a Camper Special 2.0 (stock FI setup for '75), seems to have a warm coil, too. I checked it with an infrared thermometer after my 7 mile commute on local roads this morning and it came in at 130 degrees F. I do have 10V at the coil...I had thought that was an issue but after some of the previous comments in this topic I'm thinking that's normal.

- Doug :-)

Coils are resistance devices, and therefore do create some heat. They will overheat if you leave the ignition on AND the points happen to be closed. This is true for Pertronix, too. If you happen to leave the ignition on and the Pertronix is parked at "ground" position, it will fry in minutes.

As for the resistance that American cars used to call "ballast resistors", VW relied on twenty feet of wire from the battery to the fuse box to the ignition switch to the fuse box again and back to the coil. As a general rule, anything over 10 will give a sufficient spark, measured under starter draw.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 93,996 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

kreemoweet
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Re: How hot does your coil get?

Post by kreemoweet » Fri Sep 14, 2018 7:35 pm

The good thing about having an external ballast resistor, instead of built-in coil resistance, is that it
can be bypassed during cranking, in order to counteract the inherently lowered voltage that the coil
gets during cranking. It's pretty common with the weak stock VW ignition system for the engine to refuse
to fire until the instant the key is released and starter current is cut off, letting the ignition voltage
bounce back up to normal.

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