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Discussion Starter #1
Was working on my 66 convertible and keep having issues with a electrical draw. Here’s the low down;
I had replaced the Point distributor with a HEI and ran into the low voltage issue due to the 7 volt wire resistor off the ignition switch. Ran another wire from the switch to the HEI and worked perfectly.
Recently I had been driving the car and after a hour or so the engine would just shut down in traffic and this happened 2 days in a row. The last time it happened I checked voltage on the battery and was barely above 12V so the HEI would shut down. Bought a new alternator and when I started the car it went to 14V , then would go down to 13.50 and steadily drop to .49, .48 and so on until it went down to the very low 13’s. Took back the battery and was able to get a new replacement and also picked up a new voltage regulator.
Now I need to say that I also have a electric cooling fan on the car.
Now when I start the car the voltage goes up to almost 14 and will go between 13.7 to 13.9.
I get someone in the car, have them hit the brakes and put the car into gear. When I check the battery voltage it drops to 12.51 and the steadily (slowly)keeps dropping, .49, .48, .47 and so on until it gets low.
If I drive it I have to keep my foot on the brakes and give a little gas to make the alternator give enough juice to compensate for the draw. I’m not sure if this has anything to do with the problem but the original amp gauge on the panel does not work either.
Has anyone else run into this problem or know where to start looking for the draw? I am not an electrical expert and this is driving me nuts so any help/ advice will be great!!
 

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What size pulleys do you have? They may not be spinning your ALT quickly enough at idle..?!
Also, what output is the ALT you installed?
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Is the alternator a stock 42 amp? If so, you may want to upgrade because of the electric fan. I had similiar issue and upgraded to 70amp. Also, is the electric fan wired to run constantly? It should have a thermostat so it only comes on and off at set temperatures.
 

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I second the alternator size as a possible issue. Radiator fans can draw 20A, and a stock alternator often can't keep up with that and the other loads.
 

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Switch to a 3G alternator. Find what you need at PA Performance. It is not unusual for these old cars to only produce 12v at idle, they really only charge when then RPM’s are up. Your electric fan is sucking the life out of that old alternator.
 

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Discussion Starter #7
So I think I found the issue.... the alternator I have is a 55/61...... when I took the electric fan off it shows that it’s 86A 12V, I realized that the fan is for industrial equipment application putting out way more amps than what the car can produce. Looking for a new fan this week.
 

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Your actual wiring could be a issue too due to voltage drop from excessive resistance. A bigger alternator may not fix the issue.
 

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Actually, if your alternator/regulator are working correctly, your voltage output should be around 14 volts just after starting. Then, as the battery recharges, the regulator will lower the alternator's charge rate down to 12.5-13 volts to prevent the battery from being overcharged. If your running charge rate drops below 11 volts, then you have a current draw that is more than your alternator can handle.
 
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