Hi All,

Have a 2003 nav - and coming home the other night, lots of stuff on, lights, AC, etc - things started going screwy for no reason - first the ABS system was failing, flashing on the dash, and intermittenly making some high pitched grinding noises at the wheels!! then the ADVtrack system was disabled, etc... then I'd see the system not charging error flicker, then the whole dash would shut OFF completely!

The truck kept running! even with no dash on at all....

got her home, Battery was DEAD - wouldn't even roll up a window at all...

charged it over night, started up, and drove it around the block, and all seems ok, but...

just wondering if I should be replacing the alt along with the battery? I guess batts don't last forever anymore, but this was a motor craft max bought in 2012... I checked the voltage at the battery with the car off and it was 12.2, and with it running, it was 13+ so, at least at idle, the alternator is working.

Also, at the beginning of the trip, I noticed my CEL came on... I pulled the codes and it's 171 174 - is there something notorious on 2003 Navs that I should know about? would a lower than normal voltage situation cause this (lean mixture on both banks) - I have some MAF spray for the unit, or should I just replace it? - anyway to trouble shoot the 171 174 codes - I cleared them, so I guess I'll see if they come back?

Ok, so these are 2 separate questions...

Thanks all!

 

12.2 is real low. Just a few tenths of a volt is a lot when it applies to an automotive battery.

12.8 volts is fully charged for a "maintenance free" battery, though they might measure 13.2 or so just after a drive or charging say. Alternators should be tested under load, the way to do that is turn the headlights and accessories on - heater full blast etc. Then run the engine up in neutral to 2000 or 2500 RPM and hold it for a few seconds while checking voltage at the battery posts. Should be around 14 volts, say.

Just a WAG, your battery is about done swapping electrons around, but that's a guess, it's important to check the alternator carefully as a defective battery can damage it and the reverse is also true.

 

Sounds like the battery is toast. I agree with checking your voltage with some draw and expect to see the charging rate at the battery terminals to be between 13.8-14.4 volts with a good alternator.
Keep in mind, most of the time a good alternator will keep everything running properly even if a bad battery but today with such sensitive electronics in these cars and trucks, a good solid 12.8 volt battery is mandatory.
One thing to also check is watching the alternator voltage when cold, but also hot. At first start up, bad alternators brushes and contacts can seem to work okay but once things heat up, many times you'll get a failure. Keep an eye on the volt meter regularly.

 

Please forgive me if I seem unpleasant in conveying the following information, I'm just getting tired of questions like this again and again:

battery voltage: 12.6v
Key ON: 12.5-12.6v
cranking: 10.0v or more
engine running: 13.5-15.0v

With the gauges going wacky, I believe the output cable is shorting out. My RX7 behaved identically when one cable lug grounded out on the intake just enough to turn the dash into a Christmas tree, but still keep running. Voltmeter flat lined until I fixed it, then went back to normal.

Try undoing the positive battery terminal and checking for continuity between it and the chassis. It should read infinite as they shouldn't be connected. If you see any continuity, you have a short.

 

I'm a little confused in your statement so help me understand. If I use my vom from my positive battery terminal to my chassis, I will still expect to see 12.6-8 volts. The negative side is directly attached to the chassis and would complete the circuit, thus showing current flow thru the battery.
Not sure why you would expect to see zero?

 

After the voltage tests, do a continuity test as prescribed. Sorry, i should have been clearer in illustrating that you'testing for continuity between positive and ground without the battery in the loop.

 

Got it. Battery terminal, battery post, battery cable. Can be confusing.
Thanks.