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Discussion Starter #1
What is the minimum and maximum voltage the car should be running at?
The more accessories I turn on, the lower the voltage goes, fan on high, head lights etc...

The reason I am asking because I bought a MSD 6a and dont want to install it until I know what voltage it will take.
Thanks

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69 Camaro 1977 350
Shift kit, HEI, holley 600, flowmaster delta flow mufflers
http://msnhomepages.talkcity.com/rallyrd/murfys_law
 

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You should see about 12.5 volts with the engine and all accessories off. It should go to about 14.5 with the engine running. It may take a high idle to get that. Above 15 and below 13.5 with the engine running at high idle are the danger points. Please be sure to measure voltage at the battery. Some voltage drop in the wiring harnesses is normal and can through a voltmeter reading way off.
 

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Discussion Starter #3
So you are saying to wire up the voltage guage directly to the battery instead of the accessory plug???????
 

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Not permanently, if you did that your battery would go dead when the car was sitting from the drain of the voltmeter. What I am saying is to not trust the voltage reading from the meter in your instrument cluster as gospel. When checking for electrical problems, the testing should be done from direct battery connections. It is normal to see some voltage drop in the wiring harnesses in your car. You may be seeing a voltmeter reading that is lower than reality when all your accessories are turned on, so for testing purposes, check for proper voltages directly at the battery's terminals.
 

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Agree with Chris on this. Saw a post the other day about running the headlights off a relay using the dash power to switch the relay only. When you start pulling serious current from the dash harness, things sometimes get strange. Consider the early cars had a 37 amp alternator max.
 

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If you are in fact getting 13.8 to 14.2 with every thing off that is ok. If the voltage drops as you add load to it I would check the alt belt.

I don't check the belt tension/tightness,and assume all is ok. To check it,look in the bottom of the vee in the alt pulley.If the pulley is shiney (sp?)in the bottom it is worn out replace the pulley.

Grab hold of the alt pulley and try with much force to make it slip on the belt,if you can slip the pulley by hand it will not pull the load to keep up. Tighten belt or replace belt/pulley,or both.

Larry
 
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