Overcharging 350

[capercanuck]

I have a 350 in my 1986 27' Sunray. I purchased it and noticed that when running the engine each of my two batteries are charging at 17 volts. I spoke with a friend of mine who owns and auto electric shop and he checked my alternator. It was fried. I replaced it. I still get 16 volts at the batteries when running. I should mention that I am an electrician and I have tested the voltages with a high end digital meter at the batteries. Before alternator change 16.9v, after 16.0 volts. This is still too high, I am told. My buddy told me to check the ignition circuit by jumping between it and the +batt terminal on the altenator to see if the voltage drops, and it did. It was down around 14.5v. He thinks the problem might be in the ignition circuit. Problem is he just went away for two weeks before he could go to the dock to pinpoint the problem. Does anyone have any ideas where I could begin to look, is there a common problem which might produce this type of overcharging? I'm itchy to get into the water again and I'd rather not wait the two weeks for him to return.

 

[capercanuck]

Re: Overcharging 350

Anyone?

 

[petryshyn]

Re: Overcharging 350

what kind of alternator and how many wires going to it?<br />If it has more than 1 wire, it likely has an external sense line which may be hooked to an area which is not reflecting true battery voltage. This would trick the alt/reg into charging at a higher rate. Poor grounds or ground cables will do this as well.....

 

[capercanuck]

Re: Overcharging 350

It's a delco. There is one orange wire to the +batt post and two wires running into a rubber female plug that attaches to the back of the alternator. One wire is red with purple tracer and the other wire is solid purple. I removed the plug and tested it. It appears that one line (purple) has a diode in it but the other one (red/purple) is dead shorted, it appears to be a solid wire inside the plug, according to the reading I get. The purple wire is marked 1 and the red/purple is marked 2. I saw a diagram in an online manual that shows what appears to be a diode in line with each of these wires, although it was kind of difficult to see. Would the two diodes make sense? If one of the diodes were burnt open, would that cause the condition I'm experiencing? Thanks in advance!

 

[petryshyn]

Re: Overcharging 350

Reinstall the alternator plug. Get a voltmeter or testlite.....<br />On the alternator there should be a 1 and 2 cast into the alternator housing where the plug inserts. The #1 wire should be live with key on only. The #2 wire should be battery live all the time. Its sounds like (in your case)the #2 wire is not connected to battery +. <br /><br />On old style regulators, if this sense line (#2) isn't connected to battery +, the alternator will overcharge. It sounds like what you have.....