Voltage Question
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Junior User
Joined: Aug 2009
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From: Glendale, AZ
Voltage Question
So, I have a Pioneer radio which also shows my Voltage total. I have noticed recently(never used it before) that when first starting the truck my F350 sits at about 11 Volts till I rev the engine or start moving. Eventually it picks up to about 13.5 but rarely gets over that.
Total items running would be my Radio, Sirius, and my AC.
I checked with my father who has 2 Cummins trucks and he is regularly in the 14s and also his work truck(Freightliner) also is in the 14s.
At this point I am wondering if I have an issue or not. It would appear a battery but both tested fine today. Could this be an Alternator issue?
Total items running would be my Radio, Sirius, and my AC.
I checked with my father who has 2 Cummins trucks and he is regularly in the 14s and also his work truck(Freightliner) also is in the 14s.
At this point I am wondering if I have an issue or not. It would appear a battery but both tested fine today. Could this be an Alternator issue?
Lead Driver
Joined: Nov 2007
Posts: 5,139
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like brickie stated, the glow plugs are active for 30 seconds or so during a cold start.. they take alot of current and pull your voltage down.. i wouldn't worry unless you see <13 V during normal operation..
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Junior User
Joined: Aug 2009
Posts: 63
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From: Glendale, AZ
Sounds good. I will keep an eye on it. I did notice this evening driving around I was hovering around 13 - 13.2. I may take it by a shop to see if they can run a test on the Alternator just to be sure.
Hotshot
Joined: Dec 2003
Posts: 15,368
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From: Stuttgart, Ar
Check out this thread. It'll give you a fairly simple test procedure and some things you can look for. https://www.ford-trucks.com/forums/8...lteniator.html I went through it yesterday and discovered that I had corrosion built up in some weird places on my cables that caused me more problems than I realized. I still have a fairly significant voltage drop when starting and I'm going to have the batteries load tested today.
The charging system is designed not to kick in until after the glow plug's are turned off. This keeps from burning them out prematurely by high alternator voltage. Your truck sounds exactly like mine voltage wise, but mine drops as low as 9.9 on startup. It rarely gets over 13.1 running and I know the alternator will put out 14.1 because I had it tested brand new from the box. It's rated at 135A and will put out way in excess of that if needed.
The charging system is designed not to kick in until after the glow plug's are turned off. This keeps from burning them out prematurely by high alternator voltage. Your truck sounds exactly like mine voltage wise, but mine drops as low as 9.9 on startup. It rarely gets over 13.1 running and I know the alternator will put out 14.1 because I had it tested brand new from the box. It's rated at 135A and will put out way in excess of that if needed.
Hotshot
Joined: Jul 2005
Posts: 13,834
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From: Middle Tn.
Check out this thread. It'll give you a fairly simple test procedure and some things you can look for. https://www.ford-trucks.com/forums/8...lteniator.html I went through it yesterday and discovered that I had corrosion built up in some weird places on my cables that caused me more problems than I realized. I still have a fairly significant voltage drop when starting and I'm going to have the batteries load tested today.
The charging system is designed not to kick in until after the glow plug's are turned off. This keeps from burning them out prematurely by high alternator voltage. Your truck sounds exactly like mine voltage wise, but mine drops as low as 9.9 on startup. It rarely gets over 13.1 running and I know the alternator will put out 14.1 because I had it tested brand new from the box. It's rated at 135A and will put out way in excess of that if needed.
The charging system is designed not to kick in until after the glow plug's are turned off. This keeps from burning them out prematurely by high alternator voltage. Your truck sounds exactly like mine voltage wise, but mine drops as low as 9.9 on startup. It rarely gets over 13.1 running and I know the alternator will put out 14.1 because I had it tested brand new from the box. It's rated at 135A and will put out way in excess of that if needed.
Partsman, seperate your batteries and see what the voltage diff. is. They should be close to identical and around 12.5 at rest. Good to let them set for about 20 mins. after seperation to find their own level.
Hotshot
Joined: Dec 2003
Posts: 15,368
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From: Stuttgart, Ar
Actually they sat longer than 20 minutes yesterday while I cleaned ALL the cable connections at both ends---both batteries, both negative cables at the frame, and the starter, and the alternator. They were within .1 volts of each other. I actually started the truck on one battery and it only dropped to 9.9 with glowplugs burning. I didn't have a chance to have the batteries load tested today, but I really don't think I have a problem. It's always started this way and it does fine. It's just weird that it never gets any higher voltage. The highest I saw yesterday, and this is reading through the OBDII port on my scanner, was 13.8. I just hate hearing my FASS go RRRrrrRRRrrrRRRrrrRRRrrr every time I turn on a turn signal at a stop.
