Quote:
Originally Posted by ironhead
Rick, thanks so much for your reply. Electrical is not my strong suit as you have guessed, but I will try to address each item you mentioned. My CR wiring might be a bit light at 14 ga from the fact. I had the 70 amp. alt. tested at Advance Auto, but they couldn't tell me what it put out, just that it works, which I knew. I have March pulleys, crank 6 1/4 in. Water pump 5 in. Alt. 3 in. Serpintine belt. MSD 6AL ign box. Optima 800cca 1000mca battery. My problems occur after the engine has warmed up and the fan kicks on the voltage drops from 12 1/2-13 down to 8 with only the fuel pump and fan on. A s you can imagine the car doesn't get driven much, 1500 mi. since completion in '90s. Thanks again Rick for your input.
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For comparison on my 65 Mustang Fastback,I'm running the same size pulleys as you, I don't think the pulley size is your problem....I also run as full MSD ignition and a 19" diameter 2 speed electric fan off an early 2000 model Cadillac something or other I got at a local body shop.... I have it wired on high,never had the low speed even hooked up...Not sure of it's amp draw,but it is substantial.....along with all the other things electrical found a 65 Mustang (headlights/heater blower motor/windshield wipers/am/fm/cassette radio).....
I have the old style Ford 60 amp alternator,19.95 Auto Zone reman. special that is no less than 15 years old,I did convert it to one wire to eliminate the wiring and old style voltage regulator......Optima red top battery......
At idle with nothing on other than the car running,volt gauge reads between 13.5 and 14 volts,with the fan on volts drop to 12.5 to 13 at idle.....turn on the headlights and wipers and the volt gauge never goes below 12 volts and this is at 900 rpm idle......on the road volt gauge will be around 12.5 or a little better with everything on.....
Now back to the fan.....I have it wired with a heavy gauge wire from the alternator side of the starter solenoid and into a relay....when wiring anything with a draw like an electric fan, you need to use heavy gauge wires AND a relay..........
Your amp rating should be enough,I would drive it over to a dedicated alternator shop and have them check your amp draw with various things on and check the alternator amp output, that would tell you a lot more....your alternator could be putting out 13.5+ volts but with a bad or dead diode,your amp output would be less than the alternator is rated for......also they need to check your voltage regulator at the same time..........could easily be one or both causing your problem and being your volts drop to 8, I'm betting both!!!!!!!!
I think you'll find the problem in the wiring and the alternator amp output as a 70 amp alternator should be more than enough to keep up with the draw you have.....
David
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