Hello all.

My 2006 F350 sounds like it is turning over a bit slower than usual. I used a voltmeter at one of the batteries to test while cranking. The truck motor was warm, and had been running on and off most of the afternoon. I am using Rotella synthetic motor oil in the 6.0 liter. It was around 22 degrees. My voltmeter read 12.4 prior to ignition, and down to 9.2 at starting. It shows about 12.8 after it starts with a few rpms. Normal, or is my ear right, and it is turning over a bit slow?

Thanks!

 

You should be at or above 14 volts when idle. Your alternator is a goner. You still under 3/36?

 

I would have a load test done on each battery to make sure. Cold weather will kill a battery. If they are weak thats when it will show up. You will need to give the glow plugs time to cycle off before you see more than 13 volts. When they do you should go up to 14 to 14.5 volts.

 

I am still under the 3/36. The glow plugs were done before I cranked it over. I have never had this truck say the engine was warm enough, and not cycle them for a start. They pull it down some. I had everything else except the hood light off. I will get on the load test for each battery. I hope she makes it to town this AM!
Thanks for the replies!

 

The original factory batteries are covered ONLY under the 3 / 36 warranty (ie no separate battery warranty). Also, I was told that you MUST bring the batteries into the dealership "IN THE VEHICLE". By this they mean "drive it in" OR "tow it in". You can not bring the batteries in by themselves for them to be replaced under the warranty. Sounds funny, but I guess they do not mark the factory batteries or record serial numbers to track their service life.

What you described is exactly what I experienced not too long ago. I thought I noticed slower cranks so I bought a voltmeter that plugs into the dash power point plug. Voltage was good before starting but dropped to around 9V while cranking. The problem was one bad battery - it was clearly bad on the load test. A few years ago I bought a load tester and think it is a great investment / tool.

Good luck w/ the warranty, since it is wise to replace BOTH batteries. Hopefully they agree to do so. Even if they don't, I would buy the other battery anyway - but that is just me (I rely on reliability). I do not know what choice of battery you can get under a warranty repair, but I put in two Motorcraft Maxx BXT 65 850 and love them. Great cranking power!

Your alternator will not fully kick in until the glow plugs are done cycling as mentioned before. This is built in protection for the system.

As a side note - I noticed my voltage gauge gets warm during use. I do not think it is wise to leave it in the plug when the vehicle is not running.

 

voltage should never drop below 11.5 on these trucks. your lucky it even fired up cause the ficm doesnt like 9v. you have atleast 1 bad battery as stated and yes you should replace them both. i have seen to many times where one was replaced, and it brought the other down.

also on the charging system, that is normal. the alternator does not go full field untill the glow plugs go off from a start for up to 2 minutes. it will only charge 12.6 or so untill plugs shut of then slowly climb back up.

 

Stopped by the dealership, and pulled on the tech's ear. He was curious enough to come out and check it over with me right then! They are thinking it is one bad battery. The tech was checking both batteries from the alternator. He was puzzled a bit because the passenger side battery was charging (14.4 volts)while the driver's side was not (12 volts). After a minute or so, the second battery picked up the pace. He asked for help, and another tech called the passenger side battery "the crank battery". His opinion was that it was charged first. They are still concerned about the driver's side battery, as it was not acting right, and was leaking a bit. they were also looking for a bad spot in the wiring harness between the batteries. I should know more by tonight.

 

Good luck on this. They should replace both if you whine some !!

 

I don't think that you have a starting battery. They are both hard wired together to increase the cranking amps. IN parallel it stays 12 volts but the amps double. If you have a battery lower voltage you either have a very dirty connection or something breaking down in the wiring droping some voltage.

 

well the passager battery is first inline to recharge so that makes sense if the passanger battery is shorted or weak when compared to the other battery.

 

Could someone rep BTH for me.The rep cops wont let me.

 

Done, added rep.

 

When batteries are in parallel the current will be divided evenly between them unless one is lower in charge than the other if that is possible. A shorted cell could be an example of this. In parallel, electricity does not see one or the other as being 1st. They are equal. A bad cell would be the equivelant of having two resistors of differant values in parallel.

 

thanks cj thats what i meant.

 

This is true. However, resistance does come into play here. If there is more resistance in the electrical path between the alternator and drivers side battery, than there is between the alternator and the passenger side battery, the passenger side battery will get more charge.

If the battery cable between the driver and passenger sides were damaged, or if the ground cable for the driver side battery were damaged or not making good contact at the terminal or to the engine, or the terminals corroded, etc, it is possible that the driver's side battery would show a lower voltage. Also remember that the power feed for everything but the starter itself comes off the driver side positive battery terminal and there is a pretty significant amperage draw there. I've measured it with a clamp ammeter and on my 2004 6.0L at idle it draws around 50-60 amps.

Given all that, and the OP's comment that the driver's side battery was "leaking a bit", I'd suspect that the most likely problem is that the driver's side battery is bad. I'd still check all the cables carefully, clean all the terminals and take a wire brush to all the spade terminals on both the positive and negative sides.