I have 6.0. It cranks over ok but normally needs two cycles of the glow plugs before it will fire up. All brand new injectors and the FICM is at 49 volts. The battery voltage is at 11.5 at start up and the alternator is clearly working as once running, in a minute or three, the voltage is up to 12.5 and once on the road 13.5 to 14.

As a side note, I run HID lights. one side is working the other is not until I get on the road and the voltage comes up. I am wondering if the batteries are done and the low voltage is causing my two issues.

Any advice would be great.

 

Hey ONFord, I just went through a process with similar numbers and symptoms as yours ... my glow plugs were the culprit.
I assume your battery reading of 11.5 at startup is after the glow plugs have cycled and not before?

 

I had a similar voltage issue on my 04 6.0 but i have stock headlights. Chased my tail all thru the electrical system . Ultimately the issue was the battery harness cable that connects bothg positive battery terminals. It runs along the top of the radiator.
You need to grab a muti meter and start probing around. Mine had a short and was hot to the touch due to extra resistance.
To fix it i bought Ford OEM battery wiring harness from for around $110. It runs from the starter up to the passenger battery and connects to the driver battery.

 

That was not a "short". A true short would have caused one or more of the following: Smoke, fire, or blown circuit protection devices, if any. Yours had "excessive resistance" (probably due to internal corrosion) which is the exact opposite of a short. FWIW, the cable between the two battery posts could be thought of as an intentional "short" but we don't refer to it as such.

Low supply voltage is going to be due to either one (or both) of the batteries are no longer storing a full charge or the cables/connections between the two batteries has a poor connection causing one of the batteries to not contribute fully to the demands placed on the system during the start-up cycle.

You can check for degraded connections/cables by checking for excessive voltage drop across each "jumper" cable during the glow plug cycle and cranking action. Check neg to neg and pos to pos separately and look for very low voltages across what is supposed to be a direct connection.

 

[QUOTE=projectSHO89;18421398]That was not a "short". A true short would have caused one or more of the following: Smoke, fire, or blown circuit protection devices, if any. Yours had "excessive resistance" (probably due to internal corrosion) which is the exact opposite of a short.

Good call SHO ...Thats what i meant to say.
Havent had my coffee yet and brain stuck..

 

I tested the positive lead cable today ant no voltage drop between the two batteries. When I cycle the glow plugs both batteries drop to 11.5 and when I engaged starter both battering dropped to 9.8.

 

 

make your life easier.

just go to an auto parts store and have them do the 100 amp load test.. be done with the guessing.

most do it for FREE..

 

When they do the load test can it be done with both batteries connected? Or in other words should it be done with one battery disconnected? Otherwise how do you tell which battery is bad?