Wally39

My alternator is overcharging the battery. It's putting out 18.5 volts. My question is, do our cars have some kind of electronic protection against this. I noticed when my voltmeter swings way over things shut down like windows, ABS, traction control etc. I just hope I didn't damage anything electrical by driving it home that way. I'm getting a new alternator by the way. Just sucks, because it's a new car.

cekim

In theory, any over current that resulted from over voltage would pop a fuse before doing any damage.

My guess on the transient failures you mentioned would be a malfunctioning "smart junction box" more so that damage to individual components...

Car batteries are generally lousy sources of power from an electrical engineering standpoint, so someone doing their job would have (on the sensitive parts) both under and overvoltage protection/tolerance built into the system at some point. Non-sensitive things like DC motors (window motors) which are switched off would not care or matter...

Justastockmustang

The fuses are mainly to protect the rest of the system if an individual circuit draws too much power and sensitive electronics would be damaged before a fuse would blow anyway. You're right though, sensitive parts should have built-in protection given the unstable nature of the power. They must if you made it home that way and didn't fry anything!

cekim

You are right, I should have qualified that with "serious over current". But even that would require that would indeed require that something reached the limit of the fuse by virtue of the over voltage...

It is a little odd that the smart box wigged out though - I would have expected something so interwoven into everything to have a good voltage regulator or well regulated source...

You just put in a Saleen right? Double checked the splices on those alternator wires?

Justastockmustang

You splice there the alt wires installing the saleen kit? That being the case, great catch, you're paying attention!

Wally39

Yeah, I had to splice into the wires to make the wires reach the alternator. They include everything you need. I checked it out and it looks fine. It ran great. I drove it around town for about a week. It was when I came back from the track that all of a sudden the "check charging system light came on". The alternator is putting 18.5 volts to the battery. The battery was getting pretty warm. I'm getting a new alternator today and HOPEFULLY that fixes it. Those alternators aren't cheap either. I'll let you know if it fixes it.

cekim

Sorry to hear that... Do let us know...

BTW - the reason I ask about those wires is that depending on which one it is, if one of those wires is open or shorted, then run-away charging is exactly what will happen...

Wally39

Just for the heck of it while waiting for my new alternator I went out and started it. I noticed what happens is the volt meter stays in normal range, then check charging system light comes on, then I hear a click of a relay or something coming from behind the panel on the passenger side where all the wire harnesses etc are, then the voltmeter swings way over. It only swings way over after the clicking noise.

cekim

Well, the PCM is involved with the charging system. I guess ford got tired if the extremely reliable voltage regulators from the past (sarcastic) and decided to throw some compute power at it.

The "click" is likely a relay of some form the PCM uses to influence the charging circuit, but that does not help you much...

If you are bored, you could try the debug proceedure for "over charging" in the manual which would allow you to eliminate any wiring issues...

hmm, they won't let me attach a PDF - what a bummer - I can PM or email it if you like...

Wally39

That would be great. Thank You