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Old 04-06-2011, 07:52 PM
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Mallory Unilite Ignition Issue

This one is driving me nuts. I have owned my 1968 Corvette for about 8 years now. When I purchased it I had to rewire just about everything, no problems at all after the job was completed. Other then that the car runs great!

Just recently I have been having problems getting spark. First I thought it may be the coil, put the spare on, not that. The ignition system has a Mallory 501 Unilite Breakerless Ignition. The first time I had spark issues I came right off the coil cranking the engine and had no spark (I have a makeshift device I use to check spark for anything). I was getting voltage to the coil but I was wondering if the photo eye was working properly. For the heck of it I poped the distributor cap, left it open over night. Next day put it back on I then had spark, car started right up and continued to start many times after. I didn't see any moisture in the cap the day I left the cap open and even though if there was moisture in the cap I'd still should get spark right off the coil unless the module in the distrbutor is failing.. Car does sit in a garage but it is not climate controlled. Just today, I decided to start the car up and same crap happened, no spark again. Any suggestions I'd appreciate it. I'm just wondering if somehow moisture is getting on the photo eye/receiver not allowing a signal to get to the coil....

Thanks,
Ron - Maryland

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Old 04-07-2011, 04:08 AM
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The hall effect sensor is very reliable, it's a 68..... is it still running the external voltage regulator? I had a simular problem and got the following advice from this board....... The ext reg puts a unsteady/harsh/spikey (whatever word you choose) voltage to the ing module and they tend to fail after awhile, the Chevy factory module seemed to last the longest etc.... It was suggested changing out the old ext reg and alt with a new internal regulated alternator...... best thing I every did, super simple wireing swap and an added benny is my headlights don't dim when I fire up the heater.

The diagram is from Doc's stuff
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Old 04-07-2011, 08:07 AM
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Quote:
Originally Posted by EOD Guy
The hall effect sensor is very reliable...
Unfortunately, the Mallory UniLite uses an LED, photocell, and chopper wheel, NOT a Hall effect sensor.
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Old 04-07-2011, 08:44 AM
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You might try cleaning the LED and photoeye with a small piece of
cotton soaked in alcohol. If there's a film build-up that will clean
it off. If the no-start persists, then I'd say the unit is faulty......

Also try disconnecting and reconnecting the ground wire. Might be
some corrosion preventing a reliable ground.....
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Old 04-07-2011, 11:26 AM
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with the key on break the beam with a credit card or something. it should fire the coil wire each time. what i learned about them is there is 2 things that will kill them. lose of ground or high amp batt charger. sometimes they fail all at once and other times they will take a while but not fire every time . hope this helps .
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Old 04-07-2011, 03:29 PM
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Just be aware the 12 volt is not present from the resistor wire during cranking. When you crank the engine the 12 Volt is derived from the starter solenoid, and it's feeding the module.
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Old 04-07-2011, 08:15 PM
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Unilite Issues

Thanks to everyone for making suggestions concerning my problem with the mallory unilite ignition. As I mentioned in my post... I checked everything, no spark coming out of the coil... voltage present at the coil but no signal I assume from the module in the distributor. This has only happend to me one other time this year. The car sits mostly in the garage (68 Corvette, 427 ci), I do drive it in warmer weather but not far (gas prices way too high). The last time I had the spark issue with the car (nothing from the coil) I finally decided to remove the distributor cap, lay it back with all the wires attached, and leave it open over night. Next day put the cap back on, got spark, car started right uop several times, even days after that. Same thing happened two days ago... I once again checked everything. The coil I'm using is a Mallory coil with a ballast built in so I don't need an external ballast. Well, I did the same thing, pulled the cap off, laid it back, closed shop for the night, next morning put the cap back on, tested for spark out of the coil, bingo, got spark. Put the wire back on the distributor (wire from coil), cranked her right up with no problem, even took her out for a spin... started it up several times today no issues. I didn't do anything but remove the distributor cap, and left it open over night. Wondering if moisture had gotten on the lens of the module???? Who knows. If this happens again, I am replacing the distributor with an Acell, magnetic pickup type. I checked out MSD's at my local performance shop and they wanted around 400 bucks for my chevy big block. Wow.... then I noticed in the display case an Acell distributor (coil built inside) that looks almost the same as the MSD unit. This one cost $154.00. A friend of mine who's a tech at the place told me it's just as good as the MSD... when you buy MSD you're buying the name. He hates Unilite systems, nothing but issues and easy to burn out the module. Nevertheless, this still has not answered my problems with my current distributor... oh well, life is full of surprises.

Ron - Maryland
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Old 08-14-2011, 08:06 PM
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ignition & batterys & charging

Just a friendly note=experience here - when charging a battery- 1ST.=Disconnect it - mainly the ground cable!! Then charge it. When ever we charge a battery without disconnecting the battery- we open ourselves to voltage spikes on everything ignition - that alone will kill it! Remember to physically check that Key switch to being=OFF - heck remove the keys too!! I cant even count how many times ive seen repairs come in and there is a dead battery & the keys in the ignition and it was ON!! please be sure to chack that water in the battery also??
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Old 08-24-2011, 02:47 AM
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First post here...hello!...just wanted to finally sign up, as I've gathered some good info from hotroders over the last couple years, so thought it was time to give some back if I could.

Important Note: Unilites are designed to run with stock resistor voltage setups in older cars. Most of the failures you read about are folks trying to run them with straight up 12v...and if it doesn't kill the LED module right off, it soon will. Have run them with proper stock resistor setups or added ballast resistor without trouble. Just a friendly fyi

EDIT: Just as a not to the OP's last update...just want to clarify that Mallory does not make a coil with "built in" ballast resistor. The 'resisted' voltage is determined before it reaches the coil and coils are either resistor type or are not, but they do not carry the resistor 'built in'.

Easiest way to avoid 'resistor' issues with unilites. Power a unilite with an MSD or Hyfire (mallory's version) which most people like as an ignition upgrade anyway. Then you've got a photo-optic trigger vs a magnetic one such as pertronix, dsII, etc...and that module will live for years and years.
Hope this helps

Last edited by Frankenstang; 08-24-2011 at 02:54 AM.
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Old 08-24-2011, 06:24 AM
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12 volts kills the LED

Your ignition system has two wires connected to the coil positive side. One is a 9.5V resistance wire (run) and the other wire is a 12V (start) wire. The Mallory LED is designed to work on 9.5V. When you start the engine you slam 12V into the Mallory LED switching system. That will degrade the LED and eventually burn it out. You must use a ballast resistor between the coil and the Mallory Unilite LED module. You must use a stock coil with the Mallory Unilite with the 9.5V resistance (run) wire intact.

My experience: In 1987, I installed a Mallory Unilite conversion and a high windage ratio coil on my '62 Pontiac Catalina. Within 20 miles the textile covered stainless steel resistance wire (run) from the ignition switch to the coil burned up and nearly ruined the whole harness. I removed the aftermarket coil, installed a stock coil and a new steel resistance wire but the damage was already done to the Mallory LED. I replaced the Mallory Unilite with a stock point type ignition until I could install a Pertronix (Hall effect - magnetic) conversion kit. A "Hall effect" ignition system does not care how much running or starting voltage your system has. It will function the same with either 9.5V or 12V. However, a high windage ratio coil can be used with a magnetic switching system because the Hall effect will not reduce the coil saturation (dwell) time throughout the RPM range. Meaning, an aftermarket coil with higher output voltage can be used and the output voltage will be the same at 10,000 RPM as it is at 600 RPM. With the old school mechanical point type system, coil output voltage drops as RPM increases.
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Old 08-24-2011, 06:41 AM
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the Mallory unilite runs on 12 volts. the red wire powers the module inside and is 12 volt. the coil runs on 9.5 volts just like a points set up . the #1 thing that kills them is lose of ground. if powered up it will find it's own ground which kills the module . high amp battery chargers cause all kinds of problems with electronics. a 10 amp charger will top off a battery just as fast as 40 amps.
the 12 volt start wire has not been used in years and it will cause problems with the unilite..
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Old 08-24-2011, 07:27 AM
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I buy Unilites and rebuild them for swap meets and 90%+ of the time they have a burnt out module because n obody reads directions. Unless you are using a Hyfire box you need to put in a Mallory ballast resistor.. The wiring is then straight forward. , http://prestoliteperformance.com/Por...1214M_0000.pdf ,
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Old 08-24-2011, 07:46 AM
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yes sir, when in doubt read the damn instructions. pretty simple to me. red 12v , green to coil and brown to ground. if you run the red to 9.5 it will almost run but not worth a damn then it will blow.
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Old 11-24-2012, 12:43 PM
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Unilite issues

i AM HAVING A SIMILAR ISSUE WITH MY UINLITE DISTRIBUTOR , I'M JUST WONDERING IF THERE IS ANY TYPE OF TEST THAT CAN BE MADE ON THE MODULE. ALSO, WOULD THE MODULE BE ADVERSELY AFFECTED IF TWELVE VOLTS , INSTEAD OF THE 9 VOLTS REQUIRED , WERE RUNNING TO IT.
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Old 11-24-2012, 01:02 PM
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Mallory Unilite

Ive used the mallory unilite dist. from day 1 = had only 1 problem with a butned out module. Yes -its the 12V source-check into the mallory site & look up all the teck on it -install. Make sure of the voltage before its hooked up=crank & run circuits. Yes -battery chargers will kill the thing too- yet=only fi that ignition key is left to "ON!" As most everyone does when wont start & we get flustrated!! Darn-batt 's low -get the charger & bam - hooked it up no fire ?? Keys on ?? Wonder if??
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