763 C Charging

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nobull1

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Jan 4, 2007
Messages
196
My new to me machine has a perculiar way of acting when first started. When cold after sitting all day or overnight, I start it up and the voltage meter doesn't move for the first 20-30 seconds. After that it just jumps up to 13.5 or so, and stays there forever( turn on lights-drops slightly). I can shut it off and resart, and it always jumps to 13.5. It appears to be only after sitting for hours on end that it delays charging. My Duramax does the same thing when cold, but is supposed to. Just wondering if it is a delay timer or is the alternator/regulater getting ready to go by-by.
Thanks
Brian
 

WebbCo

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Joined
Sep 19, 2006
Messages
177
Test it at the battery with a good volt meter while its running. See if it matches what the machine guage says. 13.5 seems low to me. Alternator may be saying something to you.
If so dont buy a reman/rebuilt one, I only sell new in my bobcat store, remans are returned defective all the time so no more.
 

skidsteer.ca

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Jan 20, 2006
Messages
3,853
Do you run the engine at a low idle for the first minute or so. It may take that long for the oil pressure to engage a switch, which sends power to the alt. Though that seems kinda long, time it with you watch, 10 seconds seems like a long time when waiting for a guage to move.
Is it still the Mondo alternator with the Melroe sticker on it , or has someone replaced it with a self exciting 1 wire GM Delco by now.
Some of the self exciter one take more rpm or a bit of time to kick in.
Turn the machine off for 20 mins but leave all you lights on and see if you guage still stays at 13.5 or if it slowly drops. Also it should drop a volt or two when you hit the glow plug switch.
Now when you start it does it still kick in right away and show 13.5, or does it take a little time to replace the charge to the batt, say starts at 12.5 and builds to 13.5
Really it should show 14.5 when the batt is fully charged
If you have a multi meter you may want to check your volts with that.
Ken
 

nobull1

Well-known member
Joined
Jan 4, 2007
Messages
196
Do you run the engine at a low idle for the first minute or so. It may take that long for the oil pressure to engage a switch, which sends power to the alt. Though that seems kinda long, time it with you watch, 10 seconds seems like a long time when waiting for a guage to move.
Is it still the Mondo alternator with the Melroe sticker on it , or has someone replaced it with a self exciting 1 wire GM Delco by now.
Some of the self exciter one take more rpm or a bit of time to kick in.
Turn the machine off for 20 mins but leave all you lights on and see if you guage still stays at 13.5 or if it slowly drops. Also it should drop a volt or two when you hit the glow plug switch.
Now when you start it does it still kick in right away and show 13.5, or does it take a little time to replace the charge to the batt, say starts at 12.5 and builds to 13.5
Really it should show 14.5 when the batt is fully charged
If you have a multi meter you may want to check your volts with that.
Ken
I will take the multimeter out with me tomorrow and check what it is putting out for sure(before starting and after). The amount the gage reads is not really reliable, but does tell me when it starts to charge. After it has been started(and charging), then shut off you can leave the lights on and the gage will drop slowly but soon as you start it, it jumps right back to charging(charging is a place on the meter that is higher than at any other time) . Also if you use the glow plugs the needle deflects(while holding). The time is something I will watch as well. I said 20-30seconds but maybe as you said it is not that long. I don't know if it is Mondo or not as I haven't looked as of yet. I will try to do that as well but they are talking 1” of rain and high winds tomorrow and my garage is full. I guees I was hoping to read they all did that, but nooooo that would be too easy. I will dig tomorrow and see what I can find and get back.
Thanks
Brian
 

skidsteer.ca

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Joined
Jan 20, 2006
Messages
3,853
I will take the multimeter out with me tomorrow and check what it is putting out for sure(before starting and after). The amount the gage reads is not really reliable, but does tell me when it starts to charge. After it has been started(and charging), then shut off you can leave the lights on and the gage will drop slowly but soon as you start it, it jumps right back to charging(charging is a place on the meter that is higher than at any other time) . Also if you use the glow plugs the needle deflects(while holding). The time is something I will watch as well. I said 20-30seconds but maybe as you said it is not that long. I don't know if it is Mondo or not as I haven't looked as of yet. I will try to do that as well but they are talking 1” of rain and high winds tomorrow and my garage is full. I guees I was hoping to read they all did that, but nooooo that would be too easy. I will dig tomorrow and see what I can find and get back.
Thanks
Brian
Well if it starts that all that really matters.
But the batt should show 12.3 to 12.4 volts after it has sat over nite, and should show 14.3 to 14.6 with engine running and battery charged up.
The mondo (factory) alternator has a large black plastic cover on the back of it.
A 60 amp delco will bold right on and is cheaper to buy and rebuild
Ken
 

nobull1

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Joined
Jan 4, 2007
Messages
196
Well if it starts that all that really matters.
But the batt should show 12.3 to 12.4 volts after it has sat over nite, and should show 14.3 to 14.6 with engine running and battery charged up.
The mondo (factory) alternator has a large black plastic cover on the back of it.
A 60 amp delco will bold right on and is cheaper to buy and rebuild
Ken
I went out today and checked the alternator output and found it to be 14.6, and the battery before charging to be 12.5. So as suspected it is charging proper, but still has a 15 second delay before energizing(timed it). I guess I will just let it go and see if it continues to behave this way. It is the Mondo alternator as well. If it does cause any grief in will go the GM alternator for sure.

Thanks
Brian
 

skidsteer.ca

Well-known member
Joined
Jan 20, 2006
Messages
3,853
I went out today and checked the alternator output and found it to be 14.6, and the battery before charging to be 12.5. So as suspected it is charging proper, but still has a 15 second delay before energizing(timed it). I guess I will just let it go and see if it continues to behave this way. It is the Mondo alternator as well. If it does cause any grief in will go the GM alternator for sure.

Thanks
Brian
Pretty sure this unit has a oil pressure switch. The key sends poer to the oil press switch, once the pressure comes up the power continues on to the alternator to excite it, then you volt meter jumps up. Sounds about normal.
Your voltmeter may be sufering from a bad ground or power supply making it read low. Hook you multimeter up at the back of the guage and compare the reading, maybe just cleaning the terminals on the guage will cure the reading
Ken
 

nobull1

Well-known member
Joined
Jan 4, 2007
Messages
196
Pretty sure this unit has a oil pressure switch. The key sends poer to the oil press switch, once the pressure comes up the power continues on to the alternator to excite it, then you volt meter jumps up. Sounds about normal.
Your voltmeter may be sufering from a bad ground or power supply making it read low. Hook you multimeter up at the back of the guage and compare the reading, maybe just cleaning the terminals on the guage will cure the reading
Ken
Ken
That makes sense as it dosen't seem to do it when hot. Now that I know the charging voltage is correct, hopefully I can put this subject to rest.
Thanks
Brian
 
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