Slightly low charging voltage
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Slightly low charging voltage
Been having some issues with my charging system lately. Truck is an 86 F150 with a 300 I6 and 2G alternator with internal regulator. Voltage suddenly dropped to 12.7 and didn't go any higher with engine speed, so I started investigating.
So far I've:
-Tested fusible links
-Replaced voltage regulator
-Crimped all the splices I could find that were twisted and taped
-Replaced brushes
Most of those led to no change, but replacing the brushes led to 14.0 volts at idle until I turned accessories on. With lights, defroster, and wipers on, I'm at 13.4 volts. I'm fairly new to electrical work and out of ideas at this point, so I was wondering what suggestions you guys would have.
So far I've:
-Tested fusible links
-Replaced voltage regulator
-Crimped all the splices I could find that were twisted and taped
-Replaced brushes
Most of those led to no change, but replacing the brushes led to 14.0 volts at idle until I turned accessories on. With lights, defroster, and wipers on, I'm at 13.4 volts. I'm fairly new to electrical work and out of ideas at this point, so I was wondering what suggestions you guys would have.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
That's a little low. Older trucks suffer badly from excess resistance from corroded cable/crimps, and connections at block, frame, and firewall. Excess resistance spells trouble for charging systems.
Alternator itself needs clean mounting surfaces free of paint and corrosion too. Perform voltage drop testing between center of negative battery post and case of alternator. For quick test attach heavy jumper cable from negative battery terminal to alternator case and see if voltage improves.
Alternator itself needs clean mounting surfaces free of paint and corrosion too. Perform voltage drop testing between center of negative battery post and case of alternator. For quick test attach heavy jumper cable from negative battery terminal to alternator case and see if voltage improves.
Cargo Master
Joined: Mar 2008
Posts: 2,565
Likes: 207
From: Washington
[QUOTE ... snip ...
Most of those led to no change, but replacing the brushes led to 14.0 volts at idle until I turned accessories on. With lights, defroster, and wipers on, I'm at 13.4 volts. I'm fairly new to electrical work and out of ideas at this point, so I was wondering what suggestions you guys would have.[/QUOTE]
That is normal for a 2G ALT. Light and heater fan on high, at idle (~700 RPM), will drag down the voltage. I could hear the fan change speed by applying the brakes.
So... The only real fix is to upgrade to a 3G ALT
It really OK as is, you just have to accept the limitations of a 2G ALT, I did for many year before I upgraded to a 3G ALT.
Here is an easy way to monitor your voltage while driving.
http://www.ebay.com/itm/111411914237?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
JIM
Most of those led to no change, but replacing the brushes led to 14.0 volts at idle until I turned accessories on. With lights, defroster, and wipers on, I'm at 13.4 volts. I'm fairly new to electrical work and out of ideas at this point, so I was wondering what suggestions you guys would have.[/QUOTE]
That is normal for a 2G ALT. Light and heater fan on high, at idle (~700 RPM), will drag down the voltage. I could hear the fan change speed by applying the brakes.
So... The only real fix is to upgrade to a 3G ALT
It really OK as is, you just have to accept the limitations of a 2G ALT, I did for many year before I upgraded to a 3G ALT.
Here is an easy way to monitor your voltage while driving.
http://www.ebay.com/itm/111411914237?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
JIM
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