Ignition condenser repeated failure

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Joined
May 7, 2012
Messages
250
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Location
Near Houston, TX
My Car
1971 Coupe. 302 2V - C4 trans
All,

We have a 71 driver that is in good shape. In the last year, I have had to replace the condenser 3 times. When we got the car, I purchased a pertronix flamethrower coil for it, but we are running points and condenser under the cap. The coil replacement came after we were having problems with it running rough, and getting timing adjusted etc. Didn't seem necessary, but was just trying to eliminate things. Ultimately, I found that the condenser had gone bad. I swapped the condenser with another old one and everything was fine. 3-4 months down the road I put in new points and condenser just out of good measure - I wanted to ensure the car was reliable driver.

A few months ago, we had it in the shop for an alignment, and guy reported it was "cutting out on him" during test drive. As I was leaving parking lot the cutting out got really bad, and I parked to take a look, next thing I know it won't start for anything. Firing, getting gas and all, but just won't run for anything.

I'd just about all but forgotten about the original problem I had with the condenser in this car, but after thinking it thru, and verifying good fuel, i looked for spark. Spark was irregular and frequently weak.

Coil was essentially new, points and condenser very new, yet, I can't get good spark....

After puzzling over it, I tired a new condenser, and bam - everything runs sweet again.

We continued to watch for the "cutting out", and sure enough, after a few months of running great, a few cut-outs during driving.... teh harbinger of condenser about to go out...

Last night I replaced the coil with a autozone one, and a new condenser. Works great again, no signs of cut-out on long test drive.

So whats' up? Could the flamethrower coil have been burning out condensers? Maybe that doesn't make much sense, but if it's putting out a really strong spark, and the condenser gets weakened by that extra power, it basically goes out over time? Could that be it?

I bought a "gold" duralast coil at autozone, but all of that crap is chinese, and I stuck another $5 condenser in there (surely also chinese), but I'm not sure what could be causing the condensers to go bad.

Does anyone out there have any thoughts on a flamethrower coil with points and condenser under cap? Is that just a dumb thing to do, or could it be something else in my ignition system that is causing the problem?

I'm good for now, crossing fingers on this condenser, but looking for root cause here...

Thanks for any help

Jay

 
Check and see if your resister wire is going bad. I'm not sure what the resistance is supposed to be, but I'm sure someone can chime in with that spec. That's where I'd start!

-Travis

 
I have not fiddled with a car with points in many years. It is usually the first thing I upgrade by installing a Pertronix Ignitor.

I had a Flame Thrower coil leave me stranded once after it being out of warranty by one week.

I love the original Pertronix Ignitors (mine has been working great for 19 years) but do not like the Flame thrower coils.

 
Couple of questions, with the Pertonics Flamethower coil did you connect it up to a 12 volt source or use the original wire? Pertronic coils require 12v source while OEM coils use only 7v to 9v while running thus the use of resistance wire from the ignition to the coil while running. The only exception to this is during starting when the coil is feed 12v from the starter solenoid as long as the motor is turning over via the starter. The Ford OEM coil uses 1.3 ohm resistance so if the Pertronics is different that would also affect the life of the condenser. So bottom line is Ford used lower voltage on the points system to avoid burning them out. With Pertronic ignitions they use 12v which is why their coils require 12v too so I think that you are just burning up the condensers. If you want to use that coil go with the Pertonics ignition and just eliminate the points totally. No experience with the Pertronics systems but MSD systems do the same thing and I had to make the 12v mods to my ignition system to make it work properly.

-jbojo

 
When buying my pertronix 111 dizzy, I basically had no choice but to buy the matching flamethrower coil as it is a very low ohms type. ( 0.3)

This is what is burning out your condenser. They're basically not a "normal" coil.

 
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In response to jbobo: no I did not connect it straight to full 12v. I used the original wire (that has resistance). Being a bit naive, I figured a "coil for this car" was a coil for this car, and I don't recall reading documentation that told me to do something else. That said, I'm a poster-child for not being super careful... I'm just a bit too impatient.... and only reason not to eliminate the points & condenser is simply cost. That, and, my son had to learn how to gap points to get the ignition running with "the original equipment". I can also throw a $10 kit in the glove box and when those fancy electronics blow-out, he can get it running without having to have $100 on the spot OR and EE degree and a debug laptop handy.....

But, Without taking alot more data - I think my suspicions are correct. The flamethrower coil is "too hot", and is burning out the condensers. I've already put that coil on the shelf, purchased the best china crap coil I could get (because there was nothing to be had from US vendors :-< - I asked and the guy at autozone had NO IDEA if any of his products were made in the US...), and so maybe it will work right now with a coil designed to fit the ignition system I have, including the original "resistance wire".

I will put an ohm-meter on the flamethrower, just to followup, but seems like I should be ok. I'll post what the resistance is for that coil.

I appreciate all the feedback - really helps - as usual.

Jay

 
one major issue is you cannot get a normal low voltage coil anymore.

the only place that has something is a no name knock off from china.

the aftermarket coils are all low ohms resistance to work with electronic ignitions and most likely that is burning up the condensers after a while.

i have also seen aftermarket ignition wires cause all kinds of electrical feedback problems.

i would recommend going for electronic ignition and ditch the points.

another issue is all the points are made in china junk the dwell drifts wildly on those reproduction points and that can also blow the condenser.

another issue could be years ago a former owner bypassed the resistance wire later somebody restored the points and didn't know about that.

 
First off, I wanna say, I completely get the "go electronic ignition" comments. I have done that on my car (a 69). I'd like to set that aside as an option in this case for 2 reasons: 1) Our 71 is my sons car. I buy safety upgrades, he buys performance upgrades, and as a 17 yr old in school with no job, he doesn't have $100 to throw at it. Thats our deal, and really self imposed limitation, but that is our deal. 2) I am an engineer by trade, but mechanic at heart. Cars ran for years without these problems, and there is enough farmer engineer in me that says "I can MAKE this this work". I should be able to, and it should cost less than $10.

So, given the constraint that i want (or need) this car to stick to points/condenser for now, I SHOULD be able to set it up to run that way. And there are lots of lessons than can be taught a young man in these old school methods before we just go "throw electronics" at it. So, no offense to everyone who believes that - you are preaching to the choir here anyway.

As of today, the 3rd condenser in the last 9months went out. It always starts the same, cut-out at higher speeds, very strong short and random drops in power, jerky acceleration when it should be smooth. Shortly (within miles) this turns into a car that can't even idle. Happened again to my son today on his way home from school.

Last time I worked the problem (when I started this thread), I suspected the flamethrower coil I had put in there was "too hot". So, I bought a new (china-fab) coil (duralast-gold at auto zone - whatever that means), and whatever condenser they had. In less than 2 weeks, this car is having the problem again. So I can't blame it completely on the flamethrower coil.

I stopped at O'reilly's today, and simply picked up another condenser. They said hey - We have a "lifetime warranty" on this one for $6.99. Seeing a sucker in my sights, I bought it, and figured, as soon as it goes out again, I'll come in and get my next free one. At least that way, I can keep collecting data on this until I have it fixed and zero cost.

So tonight I left the new "china coil" (auto zone duralst-gold) in there, and I put in the "lifetime" condenser in. Cars runs great for the moment….

I took resistance measurements of the coils I have laying around and I found the following:

69 original coil (yellow top) = 1.6 Ohms

71 "original" coil (black top, but came with car) = 1.5 Ohms

71 "new" coil (duralast-gold bought at auto zone) = TBD

Flamethrower #1 coil (bought for 69) = 0.8 Ohms

Flamethrower #2 coil (bought for 71) = 0.8 Ohms

Note, After I ran the 69 and warmed the coil up to 100 deg F, I measured 0.3 Ohms. I'm not sure if this reading is trustworthy as harnesses weren't disconnected for the measurement, but I am wondering if coil temp has an affect on the coil resistance - theoretically, it could. More to come on this.

Life is an experiment. I know there is a $5 PERMANENT solution out there. I'm on a mission to find it, so if you're interested, stay tuned. I'll let you know what happens.

Jay

 
I am thinking that the voltage is incorrect to the coil. The ignition system should have a resistor wire in place to drop the voltage to the coil. The easiest way to check if you have the resister wire: Disconnect the negative lead (the one going to the distributor). Then connect a jumper wire from the coil negative terminal (the one which now has no wire) to a good ground. Turn the key to "on". If you have a resister wire, you should read ~6 - 6.5v at the coil positive terminal. If you don't, you will read full battery voltage. If full battery voltage the condenser will burn up along with the points. The condenser main purpose is to reduce arcing across the points as they start to open and acts like a battery to absorb the voltage as the points open. If you have excessive voltage the condenser will burn essentially creating a short between the condenser plates and allowing the points to arc across them. At this point is where the motor will start to run rough and die. Side affect is that you will see pitting on the points due to excessive arcing across them. The arcing across the points is essentially the same as the points being closed.

The cars charging system also produces between 14 to 14.5v when the motor is at 2000rpm so if you are seeing 12v now you will actually have around 14v at the coil further shortening the life of a condenser that was designed for 7v. If the resistance wire is going bad an option would be to use a ballast resistor to get the proper voltage. I know early Dodge vehicles used these instead of the wire.

Here is a link for a proper coil for the car, should be 12v with 1.5 Ohm resistance.

http://www.macsautoparts.com/ford_mustang/ford-mustang-ignition-coil-12-volt-1-5-ohm-black-case-replacement-type.html

Hopes this helps.

 
Thanks, I was curious about exactly that - how to check the resistance wire - I'll do that today and we'll see what I find.

Do the resistance wires actually "go bad"? Have there been experiences where people had to replace them? Hard to believe a wire could lose it's resistance over time, but if someone knows the how or why I'd like to hear it.

 
the resistance wire test would just show voltage in the 9-11volt range instead of the 12-14 volt range.

i don't know if a resistance wire can go bad basically the wire is higher resistance material to cause a 2-5 volt drop in the power reaching the coil. the idea being the slightly lower voltage will keep the points from burning up. of course then people feel the lower voltage reaching the coil is the cause of a weak spark so they either bypass the resistance wire or up the voltage of the coil higher, which burns up the points.

the resistance wire could of been bypassed if you are seeing more then 12 volts at the coil with the car running.

to inspect the resistance wire can be a big deal, from memory and i might be wrong its either a pink wire with diagonal black marks on it.

or a black wire with green marks on it, it should be attached to the red wire with green stripe from the ignition switch on the steering column. the wire makes a HUGE loop behind the dash board from left to right and left again to go out to the coil through the firewall harness.

Midlife restores harnesses and he would know more then me about how they are looped behind the dash.

you could PM him and ask for some guidance on it.

at any rate i remember there is a splice from the red-green ignition coil wire into the resistance wire.

may people Cut that splice out and jumped the resistance wire to get a full 12 volts to the coil. if you find a jump then you can just reconnect the resistance wire and maybe solve the problem. now resistance wires varied wildly on resistance. some cars from the factory never saw much of a voltage drop through the wire and some saw a huge drop.

For example, my car runs fine on the resistance wire going to the electronic ignition. my buddies car would not run at all and we had to bypass it.. he was getting like 8 volts at the coil and i was getting about 12 volts. it could be that the resistance wire in your car was one of the really low ohm ones and the car always had a problem burning up points or condensers.

from an electronics ignition standpoint that is a good thing from a points standpoint bad.

but unless you find a splice or bypass then your back to dealing with the problem. that could be contributing to the the condenser failure.

the condenser is a capacitor that is suppose to help prevent arcing across the points much like noise suppression on an electric motor. a higher voltage from the coil either caused by a higher output coil or higher voltage reaching the coil input would exceed the condenser voltage rating over time eventually the condenser(capacitor) would blow. that would then either Short out the points or cause arcing that would lead to misfires and the engine running poorly.

even a made in china coil today is much higher voltage then OEM spec from the 1970s it is next to impossible to find a low voltage output automotive coil, unless you hit eBay and spend mega box for an original NOS coil. i know i tried to do that.

put it together:

a made in china high voltage coil higher then original spec, even if it looks like a yellow cap coil.

a made in china junk condenser.

a made in china Points switch.

unless you swap it out for something that can handle more spark you will just eat condensers and eventually you coil may go as well because the Dwell drift is insane with the junk china points.

I know that you can buy resistance wire. it might be possible to splice in say 2-3 feet of resistance wire inline with your coil, that would decrease the voltage and may lengthen the life of the condenser, i know it will cost much more then 10$ plus shipping to order that wire. then the question as to what specs to order.

a ballast resistor could be installed inline with the coil to drop input voltage. problem with a ballast is they GET VERY HOT, so you will need to wrap it and attach it to the engine bay apron and maybe use the apron as a heat sink, ballast resistors tend to go after a while as well from repeated heat cycles. there are special automotive ballast resistors.

a mustang ballast wire or resistor is going to run 20$ + shipping.

another option could be a diode drop. putting diodes inline drops voltage 0.6 volts for each diode you would need some pretty heavy rated diodes and i don't think anyone has ever done a diode drop for automotive application. high amp diodes are not cheap.

all that money would just make sense to save for an electronic ignition replacement.

i say just keep replacing the condensers at 7$ a pop and keep one in the trunk and save up for a replacement ignition.

 
The PO PM'ed me, and my opinion is that this car has been cobbled together with incompatible components in the primary ignition system. The first test is to determine whether there is a resistor wire in the circuit.

When I started my business 8 years ago, I purchased 500 feet of pink resistor wire. I've never used it. Of more than 700 harnesses, I've seen maybe 3 with burned resistor wires. I have seen many pink resistor wires cut and bypassed, and often harvest them from harnesses for splicing and connectors. One cannot solder the wire except with silver solder, but crimp splicing works well.

 
well, guess what guys. I got complacent, didn't check the resistor wires, and guess what... the next condenser has failed - just yesterday. Gonna have to get to the bottom of this, it's a real pain to have this darn thing going out at random times. Amazing how swapping the condenser makes it run just as smooth as glass again.

Stay tuned.

 
well, guess what guys. I got complacent, didn't check the resistor wires, and guess what... the next condenser has failed - just yesterday. Gonna have to get to the bottom of this, it's a real pain to have this darn thing going out at random times. Amazing how swapping the condenser makes it run just as smooth as glass again.

Stay tuned.
exactly what brand of condenser are you using?

has your resistor wire been bypassed?

no, a resistor wire can not loose resistance . . it either works or it doesn't but if you check it to see how much voltage it has, i think the points need to be closed otherwise it might read 12 volts.

.

.

 
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We I re-read input from jbobo and doubly read 72Hcodes notes, and, so - below is the bad news for me. I did the resistor wire check this way:

- Removed the lead from the coil negative and let it float.

- hooked up a lead from coil negative post to a good ground on structure.

- turned the key to on/run

- used my voltmeter to check voltage from + to - posts on the bat: 12.62V

- used the same volt meter to check voltage from batt negative post to coil + post. result = 12.32V

Note that I removed the dist cap, and did the check again with the points open and closed, and it made no difference in the voltmeter readings... still 12.32V

SO, our resistance wire has been hacked or ruined. I will continue to burn out condensers with this setup. Ideally, I am going to have to see if I can find the suspect hacking and reverse it, or worst case pull the harness and send it to Mid-life for an honest to goodness fix me up.

If you have thoughts on where to look for hacking.... Places that boneheads usually go to "fix" what was a seemingly low voltage, let me know. I find it very odd that this car has been hacked this way because it never had electronic ignition as far as I am aware. So, whomever did the work was not as knowledgeable as the bulk of people on this forum (or didn't have access to this internet intelligence as I do).

More as things progress.

If you have ideas on how to inspect my existing harness, find the original resistance wire, repair harness hacks and verify to proper resistance levels, please let me know your thoughts!

I have one other thought. If i buy a REAL capacitor, one rated for say 800V peak, and I find a way to replace the "condensor" with a quality capacitor - what are the chances that it won't burn out? I assume since there is more voltage, that a 0.22uF/200V capacitor (my understanding of the spec on the replacement parts) sees more current, and ultimately gives out. Will a better quality capacitor (0.22uF/800V) solve this problem even with the 12V source voltage?

Thanks for all the help thus far! Sorry I let this issue languish for awhile... I'm back at it now that it cost me an afternoon from work again!

Jay

 
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I had same issue with battery voltage on the ignition wire frying points and condenser.

My under hood harness was slightly overheated and the resistance wire may have made

contact with a switched hot wire somewhere.

I dumped the point dizzy and went with a Chevy type HEI dizzy made for a 351c that requires battery voltage

, changed the mechanical advance springs, capped the vaccum advance can

and now the motor is a screamer. (note the HEI is too tall for stock air cleaner)

If you have battery voltage for the coil wire you can get a coil with built-in resistance if you want to keep the points.

 
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Unless there is a current load on the resistance wire, the voltage will read nominal battery voltage. The drop in voltage is due to flow of current; if no current, no voltage drop.

A better test for the presence of the resistor wire is to remove the brown or red/green wire at the starter solenoid and measure resistance from that wire to BAT when the key is in the RUN position. It should be on the order of 1.5 -2.0 ohms.

 
A better test for the presence of the resistor wire is to remove the brown or red/green wire at the starter solenoid and measure resistance from that wire to BAT when the key is in the RUN position. It should be on the order of 1.5 -2.0 ohms.
When you say "BAT", do you mean the positive post on the coil?

 
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