Alternator too hot

H

Heisledg

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I've got a 1985 mercruiser 170 with a burnt up regulator so I've purchased and installed a 65 amp 3 wire Mando alternator. Positive main charge wire hooked up to solenoid post where battery wire is attached. Exciter wire to positive side of coil. Sensor wire to positive battery post. Grounded alternator casing appropriately. She starts and runs and seems to be charging appropriately any where from 12.5 to 14 volts, but the alternator gets too hot to touch after a few minutes. Charge wire is barely warm, belt seems to be aligned and isn't really warm when I shut it down cause the alternator is too hot. Any ideas?

Doug
 
H

Heisledg

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Re: Alternator too hot

Heisledg said:
I've got a 1985 mercruiser 170 with a burnt up regulator so I've purchased and installed a 65 amp 3 wire Mando alternator. Positive main charge wire hooked up to solenoid post where battery wire is attached. Exciter wire to positive side of coil. Sensor wire to positive battery post. Grounded alternator casing appropriately. She starts and runs and seems to be charging appropriately any where from 12.5 to 14 volts, but the alternator gets too hot to touch after a few minutes. Charge wire is barely warm, belt seems to be aligned and isn't really warm when I shut it down cause the alternator is too hot. Any ideas?

Doug
Click to expand...

I should have checked the current from the alternator, didn't think that would be a problem if the charge wire wasn't warm. Will do that tomorrow.
 
F

fmalott

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Messages
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Re: Alternator too hot

Heisledg said:
I've got a 1985 mercruiser 170 with a burnt up regulator so I've purchased and installed a 65 amp 3 wire Mando alternator. Positive main charge wire hooked up to solenoid post where battery wire is attached. Exciter wire to positive side of coil. Sensor wire to positive battery post. Grounded alternator casing appropriately. She starts and runs and seems to be charging appropriately any where from 12.5 to 14 volts, but the alternator gets too hot to touch after a few minutes. Charge wire is barely warm, belt seems to be aligned and isn't really warm when I shut it down cause the alternator is too hot. Any ideas?

Doug
Click to expand...

if it's a 3 wire alternator it should charge 14.5 volts all the time i hope you have a warranty on the alternator i would take it back
 
Don S

Don S

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Messages
62,321
Re: Alternator too hot

If you have the purple wire hooked to the coil, there is your problem. The engine has a resistor wire and the alternator will never see the voltage it's looking for.
Make your connection for the alternator at the automatic choke, it doesn't see reduced voltage like the coil does.

View attachment 470 wiring w alt.pdf
 
H

Heisledg

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Aug 5, 2012
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Re: Alternator too hot

Don S said:
If you have the purple wire hooked to the coil, there is your problem. The engine has a resistor wire and the alternator will never see the voltage it's looking for.
Make your connection for the alternator at the automatic choke, it doesn't see reduced voltage like the coil does.

View attachment 163072
Click to expand...

Hooked the exciter up to the automatic choke and tried it, still seems too hot only ran it for a minute or two (probably gun shy, don't want to see any smoke) casing wasn't too bad but I didn't want to leave my hand on the magnet as it was very hot. I then put a 10 amp multimeter in between the charge wire and the solenoid post, restarted it, but nothing registered on the ammeter and battery was not charging. Checked ammeter for a blown fuse and it was not blown, need more advice, thanks guys.
 
H

Heisledg

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Aug 5, 2012
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Re: Alternator too hot

Problem solved, battery needed to be charged, once I charged it, everything seems to be working fine. I'm sure the alternator was working it's butt off to charge the 950CCA battery. Need to get out on the water and run it hard, but I think we're in good shape after some dryland testing. I'm guessing the that the last couple of times we went boating the battery was not being charged by the original setup (the burning smell should have clued me in). Anyway, another conversion to a 3 wire alternator is has been completed. Thanks for the help, this is a great forum.
 
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