1968 GTO Electrical Issue - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 04-11-2019, 12:56 AM Thread Starter
 
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1968 GTO Electrical Issue

Sorry, this may be lengthy to explain, but here it goes. Back in August 2018 I had an MSD 6AL system installed includes distributor, plugs, wires, coil (old style cylinder) and control box. All was working great until around January this year. Noticed the dash lights, and head lights had this glow effect going on (dimming slightly, back to bright and so on) and after market Volt gauge needle was bouncing back and forth. My First thought was Regulator, purchased AC/Delco external Reg and installed. Same issue with lights, but now two other issues show up, (1) at Idle, GEN light comes on and key buzzer tries to buzz with engine running and (2) now getting Engine Run-On (keeps running after key is turned off, and eventually 20-30 seconds later shuts down). So, I had the Alt. checked, it came up as BAD, so I replaced it, same issues. Engine harness had been hacked some before I got the car, so ordered NEW OEM engine harness. Installed new harness, same issues. I had changed out ignition switch last year, so thought maybe it was bad, so re-installed the original switch, same issues. In researching the MSD 6AL I found that the issues are known to happen. To correct the problems, I had to install a Ballast Resister in the system. I installed one and the Engine Run-On was corrected, but still have the original glowing effect and the GEN light/buzzer issue. MSD also includes a Diode that gets installed on port 4 of the Regulator. I put the Diode in and nothing changed. Also thought after market Volt gauge was bad, so installed all new gauges (oil, water, volt), no change. Last resort was getting another 6AL control box in case mine was faulty. Installed new box and same issues. I am at a total loss now with why the glowing effect and GEN light wants to come on. At Idle the GEN/buzzer comes on and with added RPM the glowing effect and Volt gauge bouncing happens. What could possibly be doing this? I practically have a whole new electrical system now. Thanks for any help you can provide.
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post #2 of 9 (permalink) Old 04-14-2019, 02:25 PM
 
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Garage
FWIW - I had these symptoms last year at this time.
Turned out to be a short under the dash (courtesy light)

DK

<)))>><

"Pray as though everything depended on God. Work as though everything depended on you." - Saint Augustine
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post #3 of 9 (permalink) Old 04-15-2019, 10:09 PM Thread Starter
 
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PROBLEM SOLVED: The externally regulated alternator was not producing enough amperage to the system. Installed a 100 amp internally regulated alternator, jumped the external regulator wires (F-to-3, 2-to-4) and all is working with 14 volts flowing and no issues at all.
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post #4 of 9 (permalink) Old 04-22-2019, 10:14 AM
 
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Good job, thanks for the info..
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post #5 of 9 (permalink) Old 04-23-2019, 08:01 AM
 
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Originally Posted by Bill68GTO View Post
PROBLEM SOLVED: The externally regulated alternator was not producing enough amperage to the system. Installed a 100 amp internally regulated alternator, jumped the external regulator wires (F-to-3, 2-to-4) and all is working with 14 volts flowing and no issues at all.
Can you post the part number that you bought ?

Currently I have a stock 10 dn alternator. I took the alternator apart for a cleaning and noticed the graphite brushes are getting low. Unfortunately it appears the brushes are almost impossible to find and it is easier and cheaper to just buy a remanufactured 10 dn unit with a life time warranty for ~$50. But as we all know, stock isn't good enough, and maybe I really should get a 10 si (internally regulated), 100 amp alternator instead.

Well after doing some reading on the www, it appeared the 10 dn and 10 si were supposedly the same size case and therefore the "upgrade" would be easy and all that was really needed is to convert the plug and jump a few wires that go to the external regulator.

1965 GTO Convertible 3 speed tri-power drum brakes originally

Current setup:
400 cu in with tri-power
4 speed Muncie

Last edited by cij911; 04-23-2019 at 01:00 PM.
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post #6 of 9 (permalink) Old 04-23-2019, 05:07 PM
 
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You really want a 12SI alternator. They have better cooling, better rear vents, a shrouded front fan...the alternator sucks air back to front to cool the windings.

Case is the same size. 10si only went to 63 amps originally, if you go too high you lose cooling. Alternators fail because the heat destroys them, heat creates resistance in the windings. You don’t want a bigger output with more windings that you don’t even need, because now you have to cool those windings.

If you are not for original, the 12SI is much better at cooling and amperage goes higher than original 10si. I know they sell aftermarket 10si with 100 amps, hey guys always say I got a 140 amp alt, etc. Maybe it is working great....depends on cooling and who made it.

A good one I use is a 12SI 78 amp, these originally came on a 85 Pontiac Firebird. You can get 12 Si in 94 amp as well. I just don’t want to cool down what I don’t even need.

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post #7 of 9 (permalink) Old 04-23-2019, 05:14 PM
 
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I recommend that you read...”Dell Remy 10 so and 12 so Alternators,..Mad Electrical”

Just google that it will come right up. That is Mark Hamilton, I have talked with him and I use his MAD Electrical wiring system. Mark knows these GM electrical and hot rod systems like the back of his hand. He was a shop foreman for GM dealerships specializing in Electric. Super guy.

Read his alternator paper, it will help you make a good decision on what to get.

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post #8 of 9 (permalink) Old 04-23-2019, 05:15 PM
 
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Delco Remy....typo sorry
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post #9 of 9 (permalink) Old 04-24-2019, 12:00 AM
 
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Originally Posted by Lemans guy View Post
I recommend that you read...”Dell Remy 10 so and 12 so Alternators,..Mad Electrical”

Just google that it will come right up. That is Mark Hamilton, I have talked with him and I use his MAD Electrical wiring system. Mark knows these GM electrical and hot rod systems like the back of his hand. He was a shop foreman for GM dealerships specializing in Electric. Super guy.

Read his alternator paper, it will help you make a good decision on what to get.

Mark is a great guy - super knowledgeable and generous with his time. I have his electrical kits on my GTO and Bel Air!

1965 GTO Convertible 3 speed tri-power drum brakes originally

Current setup:
400 cu in with tri-power
4 speed Muncie
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring

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