F355 Alternator Problems - Latest Update

i had my AVR tester hooked up to the car in the shop. I wiggled that shut off switch like no bump ever would. I tapped it with a hammer, I even turned it to the half way point, and it never failed. I gave the car back to the customer after 2 days of trying to get this thing to fail. We'll see what happends tomorrow..

 

This customer wouldn't have an inverter for his DVD or laptop that he plugs into an overfused cigarette lighter, would he?!

 

OK.....Here's the latest:
Dealer checked out everything they could check out. Kill switch, all alternator wiring, etc. All checked out good. Installed another alternator.
Took the car for 50 mile test drive. All worked perfect. I pick up the car. About 15 miles down the road, the battery light comes on. About 4 miles later, it goes off, and I could tell that the battery was charging again, because the A/C fan got slightly faster when this happened. (I forgot to bring my voltmeter to plug into the cigarette lighting to monitor everything as I drove home. The light stayed off from this point all the way home.

What could be happening. A fried alternator doesn't come back to life. What could cause it to stop working and then start working again? What can I check? The dealer said that they completely re- put on the ground strap to the alternator and engine block, so I know that connection is good. I checked the kill switch....it does not loose continuity with any "jiggling".

Perplexed!!

 

I don't know, but...when the battery light comes on again, if you can safely pull over, leave the engine running and open up the passenger footwell. One by one remove each relay that does not pertain to keeping the motor running (e.g. leave the full pump and ecu relays alone!).

As you remove each one, check to see if removing that relay turns off the battery light.

You should be able to rule out a large amount of your circuits as being your problem this way.

If necessary, repeat with the relays that are under the felt liner in the front hood (left/US driver's side).

 

Well,

I put both of the negative cables on the kill switch over to just one of the terminals (bypassed the switch). Took the car for a drive while monitoring the voltage with a volt meter hooked into the cigarette lighter. Drove for about 20 miles. No problems! Started out at about 14 volts, and worked down and stayed around 13.5. I think that the chances of the problem being cured is about 1 in 10, but just maybe this was the problem! I don't think that the switch itself is bad, but I think that maybe a good connection from the cables to the terminals on the switch could have been the culprit. I don't know. I will drive it again tomorrow, on a longer trip. I'll let you know!

If the battery light DOES come back on, I'll start pulling relays and maybe I'll come across the circuit causing the problem.

AZFerrari

 

Good man!

 

perfect!! good luck, hope it works now!

 

Repost..
Have you checked the heavy cables at both the junction box in the rear (engine bay) and under the dash in the pass foot box? Remove the COM bar and wire brush, inspect the plastic housing for distortion / melting. Found problems here numerous times.

Dave

 

I have a customer car with same symptoms, run fine then light comes on, I have just towed in and found the rear connector block melting, I would guess that a poor connection causes the alternatot to go to full voltage creating more heat and poor contact until the alternator quits also. I am replacing the alt (new), connector block and recrimping the wire ends, and battery. Update y'all later.

Go England!!

 

Even though they looked good, I removed the three heavy cables and the
common bar from the right side of the engine bay, under the removable cover.
I wire brushed everthing with a dremil tool wire brush. Made all the metal nice and shiny. Also dremilled the threaded posts. Put everything back together. Sprayed all with battery terminal anti-corrosion spray. This just leaves the passenger footwell cables, which, once I pulled off the metal cover in the passenger footwell, I could not find. Are the
heavy cables under the fuse block? Do I need to remove the fuseblock to get to the heavy cables? What is the plastic box with writing on it on the floorboard, underneath the fuseblock?

AZFerrari

 

I have had similar issues with my 348 alternator. in fact the light flashes at high revs other wise its off. Cant understand what to do. I have had the alternator serviced here, they seem to think its ok, my battery does'nt drain: so hopefully I am ok. any views?

 

My battery never drained either. That's why I think it is an "open" or "resistant" positive or negative battery cable condition, rather than a short.

 

If the alternator light is controlled by the ecu, please disregard the following:

take a peek at the schematic if you have it and see if there is a diode in the alternator light circuit. Since the '89 328 had one, I'd guess the later cars do too.

if so, that means the voltage at the lamp is higher than the voltage on the D+ wire coming from the alternator. The only reasons that would happen are:
1] problems with the voltage regulator or diodes (but you replaced those)
2] bad grounds
3] the D+ wire is intermittently shorting to ground or some other lower voltage circuit.

a voltage drop through the 12V circuits (e.g. the positive battery cable or the fuse box/relays/ignition switch) would result in the D+ wire having a higher voltage than the lamp, and the diode would block current flow so the lamp wouldn't light....assuming, of course, the diode is ok.

I dunno why the diode is there, since it will hide potential problems. Maybe there is just an inherent design issue that causes lower voltage at the lamp than the alternator, so the diode prevents the lamp from glowing dimly all the time.

If there's no diode, then voltage drops in the +12V circuits could be the problem. I'd use a meter and using the B+ and/or D+ outputs on the alternator, poke around in other parts of the 12V circuits looking for a voltage difference. The lamp lights when there is sorta a difference in voltage between B+ and D+. The "sorta" is because while the D+ is directly connected to the lamp, B+ has the battery hanging on it, and has to go though the ignition switch and probably the fuse box before it gets to the other side of the lamp. Lots more opportunities for bad connections to drop the voltage.

 

Probably your voltage regulator is failing....

 

Youre right. Am having it replaced.

 

Well, after all of my alternator woes, I think that either bypassing the kill switch or wire brusing the 3 positive cables and the common bar in the engine compartment must have done the job! No problems with alternator since doing these two things. I am vigilently monitoring the voltage of the
charging system with a volt meter plugged into the cigarette lighter. Typically, it settles in at 13.6 volts....perfect. Neither the kill switch or the positive cables and common bar showed any visible corrosion. The kill switch was not "loose".....jiggling or banging it did not make it loose continuity, but
who knows. Anyway, all is well. I hope this ends the "alternator / year" saga!

AZFerrari

 

Congrats! Nice work. You fixed with a little elbow grease and brain power what a Dealership couldn't "rectify" (pun intended, I'm just that kind of guy) with large amounts of money, new parts, and multiple attempts over several years.

Which is to say, you've just discovered firsthand why so many of us do our own work on these cars.

If you want it done right, then you've got to be willing to get dirty.

 

great news!!!

do you have pics of the 3 positive cable you wirebrushed? for illustrating other owners with the same problem

thanks
ROLO