My 01 Ford F350 PSD has been having problem starting after a few short distance drives. I have noticed when watching the volt meter on the dash that after starting the voltage reads below 12 volts for up to 5 minutes after starting. It then returns to normal charging levels. The other day I had been doing some short distance driving and so at one stop I left it idle to let it charge up the battery but when I went to leave I noticed that the volt meter was below 12 volts and as I tried to drive away the engine would power surge. Normally on large trips I have no troubles with starting after a long drive but if I do 2 or 3 short trips in cold weather I'll be left stranded. When testing the batteries(when charged up) individually with a load meter the batteries test fine and when the charge system is showing normal on the dash the external volt tester shows 14+ volts. The other thing I noticed is that when the battery charge is depleated the fast idle engine warm up cycle doesn't work.
A few questions: Is it normal for the charging system not to go directly to full charge imediately after starting? How accurate is a load test on larger truck batteries(checked individually)? Is it normal not to charge(even lose charge) when just sitting and Idling(providing it doesn't go into fast idle)? How much will the glow plugs affect the charging system in cold weather? Where do I start to look if there is a problem?

 

Other than you starter, I would think the glow plugs have the biggest power draw. If the Glow Plug Relay is not opening as it should, that could be what you are seeing with the lower voltage. You have to have a miminum of 10.5 volts for the PCM to work. If you are below 12v, you will have all kinds of problems. Check you GPR next time after starting with a multi meter and make sure it is opening up after a minute or two. the batteries need to be unhooked to check them with a load tester. Both needs to be good and both needs to be replaced if either shows weak. It sounds like a new set of batteries are in you near future. Also, you should have your alternator checked and make sure it is doing its job.

 

You have a bad alternator,.The alternator has blown a couple of the diodes inside of it..This will cause exactly the problem you described.When this happens the alternator will have a very low charge rate.this is the reason you volt meter is so slow coming up .also when this happens the alt cannot make enough current to meet your trucks demands.The voltage will show good but you will not have enough amperage output.Also When alternators do as yours has the alternator makes what is called (bast#$ard current)this can also cause things to act up on the truck.
It is hard to detect this problem with the unit on the truck.But if you will take it off and have it checked The problem will then show up.

The reason the light is not on is because the diodes have blown closed fooling the circuit into thinking everything is okay

 

I second the alternator, go get ya one and see if it helps.

"go get ya one" i know I'm saying it like alternators are cheap

 

A simple voltage output test of the alternator may not be sufficient. You should remove it and have it tested on a test stand for proper amp output. This is the best way to make sure the alternator as well as the built in regulator are good.

Edit: What everyone else said. I was too slow.

 

Another vote for the alternator. On extended trips you're maintaining a high enough RPM to put more amps out and keep the battery charged. On short trips, or at idle, the slower average RPM won't produce enough for the batteries. I'd get it tested fast before you ruin the batteries too. You might also do a quick check on the wires on back of the alternator. Make sure you don't have a loose or semi-broken connector back there.

 

Most good auto parts stores like Advance or NAPA can test the alternator seperately on a test stand for the proper amperage output. As stated earlier it's the best way to make sure that the alternator as well as the internal regulator are both working properly. Also, be sure that both batteries are fully charged and tested before you drive off with a new alternator othewise you could damage it. Good luck!

 

And make sure they put the new alternator on the test stand.

 

Keep in mind on a cold engine, the glow plugs with work for a minute or so, resulting in a voltage reading around 11 - 12 volts while running. As soon as the relay kicks off the voltage will increase up to charging voltage of about 14.4 volts.. I have a digtal voltage meter plugged into my cigarette outlet all the time, so i watch the glow plugs turn on and off. But once the engine is warm and on your next start up, the glow plugs will stay off.. resulting in 14.4 volts right after start up...

 

I tested the charging system again. Driver Side Battery tested o.k., Passenger Side couldn't hold voltage under load so I'll have to go battery shopping I guess.

Alternator specs:
2 Batteries w/o truck running: 12.9
Alt. volt @ idle: 12.5v (except directly after start where glow plugs seemed to bring it down to 10v)
Alt. volt @ 1500 RPM: 13.75 volts.
Alt. Amp @ Idle under heavy current demand: 20 Amps
Alt. Amp @ 1500 RPM under heavy current demand: 60 Amps

Do you think the alternator is needing rebuild/replacement as well or is it just the one battery causing all this problem. When I tested the batteries earlier this winter they both seemed to test o.k. but still was having some problems.

 

Those alternator numbers are low.

 

Another vote for the alternator. In my experience, an alt that pulls low numbers can also cause power spikes, I've seen an overactive alternator completely nuke a perfectly good battery.

If you say its "surging" it might have caused that battery to go bad.

 

Sounds like the alternator to me. Also, if you show one battery as being bad you should consider changing out both batterries! I know it's double the cost but, trust me if one is bad the other is not too far behind! Just my $.02.. Good luck

 

I replaced my alternator and both batteries. The voltage is at 14.4 at idle and I can start my truck even after short runs! Thanx for all your input

 

Glad to hear you got it fixed.
One thing that I would do now is to put a jumper wire between the alternator post and the battery, and also an extra ground wire between the body of the alternator and the ground post on the battery.
It offloads the charging current from the wiring harness and provides a better path for the electricity to flow when charging the batts.
All the truck's main harness has to do then is to run the truck.