I've got an '05 F150 XLT Crew Cab with the 5.4 engine. With the key on, engine off, the red battery light lights and goes out on start up but about 30-45 seconds after start up the red battery light comes on. My volt meter is only showing battery voltage at the battery (about 12V) when running. I put in a new Bosch alternator and have the same results. After checking a wiring diagram, I checked the three fusible links to the alternator and they were ok as well as the #15, 5A fuse. I have battery voltage at the B+ and AS terminals (supplied by the fusible links) but nothing at the I or S terminals ( lt/grn/red & lt/grn/org wires). I'm not sure where to go next. Anyone have experience with this?

 

I would jumper to the ignition wire then check to see if there's 13.5+ at b+ just to check. Then follow the I wire back to what ever is the problem.

 

Look to a blown fuse link C going to AS terminal. Other hOT is the B+. Look for a bad wire or crimp at the terminal of a connection. Canbus + and _ are the other terminals at the alternator, and communicate with the cluster for CanBus activity. Also test those connections. Might be damaged. Be careful here. You probably have an open battery cable at or near the battery. A bad crimp, corrosion damaged, even broke cable with only a few wires making it. Having the alternator tested along with the battery will tell you if both are good, but not that you have a bad connection/cable. A bad cluster is not good. Does it function. Try running a HEC test of the Cluster/CanBus system. If it passes it tests it is good.

To enter the HEC ( Hybrid Electronic Cluster) Dealer Test Mode, depress and hold the instrument cluster SELECT/RESET button and then turn the ignition switch to the RUN position. Continue pressing the SELECT/RESET button (five seconds) until tESt is displayed in the odometer. The SELECT/RESET button must be released within three seconds of the odometer displaying tESt to begin the dealer test mode. Depress the SELECT/RESET button to advance through the following steps until dtc is displayed. Depressing the SELECT/RESET button will display any continuous DTCs stored before proceeding to the next step.

 

Uh the voltage regulator which is 130 amp is probably bad. Had this happen to mine. It is a separate part you can buy at your local auto parts store.

 

Papa Tiger... thanks for the info, will check these items tonight when I get home. Everything works in the cluster, only questionable item is the outside temp display. It is way off, thought it might just be the sensor in front of the rad.

Chris.... I didn't think there was a regulator since the PCM regulates the field current in the alternator.

 

When you do the HEC test you can start up the motor and test that option like voltage with it running and see what the Cluster reads. If it passes its tests the CanBus is good, if not it is probably the cluster malfing, unless you have a DTC for the PCU. Note a bad battery will not take a good charge. A bad cell is just that, it may grudgingly start but not charge up. A faulty brush in the alternator can drive you nuts with on again off again status of charging. A rebuilt alternator many times has a bad split ring and the brushes malf on it. Voltage can go 14V + down to low bat voltage. Good luck

 

There is a regulator.

 

Papa Tiger.... I did the HEC test and got these codes "D950, 9352, 9318, and D900". Also did the voltage check like you suggested and it reads "11.6 volts". I guess I need to know what those codes mean. thanks again.

 

Your mostly worried about P codes. Those are cluster manufacturer engineering codes. If the cluster passed all the tests, displayed good results with each test then it is working well with the canbus. The 11 volts is not so good. That is now battery voltage. I would hook it up to a battery charger and see if it charges fully overnight. Then have the Alternator tested at the store. If you had a direct volt tester that hooked over the cables you could read the voltage/amperage coursing thru them and know if they are ok. Test starter amperage etal. Check your connection at the alternator very closely. Also grounds can be very tricky. Make sure yours are clean and tight.

 

Ok, I got some info from a mechanic. the 9318 code is low battery voltage, 9352 is a key in ignition failure, while the D950 & D900 are communication codes. He felt the dead battery might be the cause of all of them. suggested erasing the codes and see what comes back. seems reasonable.
told him about the no power on the "I or S" wires and he felt I could apply 12V to the "I" terminal and see if it charged then. Not sure I want to mess around jumping wires and possibly shorting out the PCM. How do you guys feel about this?

 

I wouldn't. Just because of how easy it can be to fry something, and a PCM for a F150 reman is around 700 bucks, and thats from a auto parts store.

 

Kind of what I am afraid of happening too. POOF and all the magic smoke escapes.
Anyway, he cleared all the codes, run the truck and a P0622 set. It has to do with a generator field circuit. I need to test the wires between the alternator 1 &2 terminals and 22 & 23 at the PCM. Either wires need repairing or a new PCM. Here's hoping it's only wiring. Will post back tomorrow with results.

 

Your cluster did its tests perfectly and
canbus is comunicating. Your alternator is malfing, probably brushes or slip ring is bring about field warning. 'replace it with warranty one. 'first charged up your low volt battery nothing works well on low volts and you cant get it tested at the store the way it is.

 

Posting back here with what I found wrong and something to watch out for on your F150's. Found a broken wire in the harness about 18" from the alternator where the field wires leave the alt. harness and join the harness going to the PCM. There is a connector there (for the field wires) and the wire doubles back over the connector and that is where it breaks, tight against the connector. It was the lt. grn/red wire (#22 at the PCM). I simply eliminated the connector and soldered the wires with heat shrink over them. On start up I had 14.7V at idle and it slowly dropped to 13.9 after about 1 minute of idling. Have been driving the truck all weekend and all is good.
Thanks to all for your suggestions and help.

 

Way to solve a tough one. A broken wire can be hard to find. Put that one in a topic too so people can get it when Search/looking for a charging problem.