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64Joker 09-14-2012 04:48 PM

Blowing fuse(s) at ign/acc at fusebox
1 Attachment(s)
What type of analysis or trouble shooting can I apply to the following problem:

Make: Chevrolet
Model: Impala SS
Year: 1964
Engine: 327
Tran: 350 Auto
Coil/Dist: Mallory HEI

When attempting to start the car, 20amp ign/acc fuse blowing when I turn the switch to the "on" position, I can't even get to the "run" or "start" position!

* See attached doc for ign diagram.

EOD Guy 09-14-2012 07:25 PM

I assume this is the same problem as in your other 3 posts?

You will prob get a better answer if you state everything that led up to the event of it not starting...... ie..... you installed the elec fan.

Somethings got a direct short

I'd start at the starter crank wire or "S" terminal, netural safety switch if it isn't them, then i'd unhook your toggle, relay, fan setup and see if that allows you to crank it. If that doesn't work, try unhooking your dizzy pwr and see if it'll crank etc... when you get it to crank, hook the dizzy pwr back up etc......

64Joker 09-14-2012 08:17 PM

My apologies EOD Guy!

Yes, the previous posts are all related.
I did previously disconnect all of the fan and toggle switch connections as suggested and replaced the blown 20 amp ign fuse, but the new fuse blew also.
I will follow-up with your other suggestion with the "starter crank wire".
Thanks for your patience, I will try to keep future posts in line, I'm just getting a little frustrated with not have more electrical knowledge.

EOD Guy 09-15-2012 04:38 AM

It's all good.

64Joker 09-20-2012 02:19 PM

EOD Guy: Follow-up
Here's a recap of what tests I've performed so far:

1. removed ign module to have it tested, however every auto store and auto electrical shops (most reputable ones) said that after market modules can only be tested while module is installed in the dizzy. The module test machines they have can only test stock type modules! I can not test the mod unless the car is not blowing ign fuses!
2. The wires to the "S" and "R" starter/solenoid check good for continuity via multimeter and physical appearance.
3. Removed the ignition switch and noticed the housing was a little loose, so I removed it, inspected it for burnt wires, all looked good.
Re-Installed the ign switch, tightened the housing real good and the engine began to crank now, but it was still blowing the ignition fuse.
4. Physically inspected all other wires, under dash, connected a 12v light to ign fuse connection and went through disconnecting most everything I could track down to see if the 12v light went off while in ign switch start position, no positive results.
5. I removed the 4 pin connector to the voltage regulator and noticed that the ign system no longer blows the ign fuse while the ign switch is turned to the "on" position and the engine still cranks (but of course the engine will not start due to the voltage reg being disconnected). Is this a valid test to warrant replacing the voltage regulator? Not giving up yet!

64Joker 09-20-2012 06:41 PM

EOD Guy: Follow-up Part II
Not sure disconnecting the voltage regulator proves anything at this point (other than I'm not blowing the ign fuse anymore. But with the voltage regulator disconnected, can I perform a HEI dizzy module test now?

EOD Guy 09-20-2012 07:31 PM

OK you're getting somewhere........ One question, do you have the orig alt or a new internal regulated one?

If it's the old alt...........the voltage reg has a ground via the housing base and a wire (if I remember correctly)........ unbolt the reg from the fire wall and disconnect the ground wire (if it has one) reinstall the hot wires and see if you still pop the fuse....... if you don't..... I'd guess the reg has gone south. Now if it were me I'd put a new internal regulated alt on it and do away with the old reg. You can leave it bolted to the firewall and hook dummy wires to it, if you want the orig look etc...... In my 67 I did the swap and it solved all the dim, blinking headlights, tail light problems, heater etc...... and the reg

64Joker 09-21-2012 10:37 AM

EOD Guy - Follow-up
I have an "External" alternator original setup:

As suggested, I unbolted the volt reg from firewall, removed the ground, then reconnected the hot wire harness and the ign fuse did NOT blow.

After removing the volt reg, I inspecting the back of it and it looks pretty darn corroded and rusted!

So, it wouldn't be that expensive to replace the volt reg at this point.

Would it make sense to test the HEI dizzy module at this point. Would it be a valid module test without the volt reg installed, or should I wait to run the module test after replacing the volt reg.?

SSedan64 09-21-2012 10:33 PM

Unregulated Alt output may damage the Module.

Reg Info:


Does your local Auto Store test the Module with Distributor installed in engine or just need the Module mounted in the Distributor??
Took my Module to AutoZone & they tested it without Distributor.

EOD Guy 09-23-2012 02:37 PM

I would NOT start it untill you corrected the reg problem..... voltage spikes reek havoc on elec components. Odds are that's your problem.

If I were you I'd look at how much the reg costs vs a new internal regulated alt. Super easy to convert to the new alt..... basicly you install two jumpers at the old reg, add a 8-10 gauge from the alt back to the orig factory splice (to handle the need increased amps) and change out the pig tail.

Best thing I ever did for my car..... up till I re-wired it with a modern wire/fusebox kit.

64Joker 09-30-2012 11:01 AM

To: SSedan64

Originally Posted by SSedan64 (Post 1592801)
Does your local Auto Store test the Module with Distributor installed in engine or just need the Module mounted in the Distributor??
Took my Module to AutoZone & they tested it without Distributor.

The auto stores in Nor Cal (Northern California) will test your mod out of the distributor, however they advised that my specific "Mallory" mod would not qualify for their test machine, thus I will have to execute my own mod test once I resolve my electrial issue when I get back to California next week.

64Joker 10-11-2012 01:14 PM

I'm back to the grind after a 2 week vacation in New York!

I replaced the voltage regulator and capacitor, I'm no longer blowing fuses when ignition switch is turned to "on" or "run/start". Attempted to start engine, it cranked but did not start.

Executed 2 tests on the Mallory distributor module, but it failed! The volt meter displayed a continuous variable reading on both tests (sensor unblocked, then blocked). Time to replace the module?!

EOD Guy 10-11-2012 04:49 PM

If you have 12v to the dizzy during crank and run, that'd be my guess...... I keep a spare module in my car...... seems I blow one every other year or so.....used to get me stranded, now that's the 1st thing I ck/change...... accel has them for about 40 bucks, but they arn't the best QA, IMO. The OEM chevy ones are expensive but the QA is much better..

BTW glad you got it figured out.

64Joker 10-12-2012 09:27 AM

EOD Guy Info

Mallory now carries a "performance power filter" that will protect the module, it cost about 45 bucks, probably well worth it!

I'm gonna order the new module and protector today, I'll let you know when I get the engine started! Thanks for all your help, it's appreciated.

64Joker 10-24-2012 12:19 PM

I installed the new dizzy module and module power surge protector, tested good at 12v and engine started with no electrical issues!
Tested the new electrical fan toggle switch setup with no issues there!

I'm guessing that the initial issue was caused due to a incorrect wiring configuration at the electrical fan toggle switch wiring which caused a spike to the dizzy module which blew the module!

Ready to "Rock n Roll"!

Thanks for all your help forum! :)

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