Electrical Issue in Wife's Car

[Doppleganger]

My wife's car has been trouble free for about 4 yrs now. About 2 weeks ago, the battery and (a faint) brake lamp came on. I've found from previous cars that a battery lamp plus anything else can usually be backfeed from a bad alt diode. So I replaced the alt, no lights and all is well. Til yesterday. Again, both lamps came on. I checked the battery - heavy corosion on the neg terminal (both have no-cor pads too). I removed it, cleaned it up well and replaced the cable. No lights again. Tonight - went to the store, no issues. When we came out, the lights came on again. I have a feeling headlights, heater blower, etc...any bigger load is whats setting it off. Both times I drove about 5 miles (with bright headlamps) so it wasn't like it died out or anything.

I checked it with a DVOM - 14.48v at the battery so the alt is putting out. Turned the car off and its 12.8v at the battery. No idea if its an intermittent issue with the alt or a bad cell in the battery. Battery is a 3yr old Interstate. Car doesn't have an actual volt gauge (but will).

Open to any ideas - similar experiences, etc.

THX fellas.

 

[bucket]

Going off memory here... Toyota Avalon?


Is the only problem that the indicator lights are coming on?

 

[Doppleganger]

Going off memory here... Toyota Avalon?


Is the only problem that the indicator lights are coming on?

Subie Outback. As far as I know.....the lights are the only 'issue'. Last time I had an alternator fail, the headlights dimmed and the dash lights and gauges all had seizures, just before the car shut off and died. This one hasn't done any of that (yet?).

The alt is a reman, so I always doubt reman'd electricals at the first issue. My only plan at this point is to take it back and swap in another - then have the battery put on a slow charge and load tested. If the battery is ok, and the lights come on again - return it for $ back and buy a "new" alt (IIRC Delco makes a new one for this).

This kind of BS never happens in June. lol

 

[bucket]

Well, I don't know where I got Avalon from, lol.

I'm not familiar with those Subarus at all. Of any year. But, a schematic of the starting/charging system and also the gauges/cluster is probably the place to start.

Also, there's a place called Hite's on the West side of Columbus that still rebuilds alternators, aIong with other parts. They do top notch work.

 

[Ricko1966]

Charge the battery and then check for AC ripple.Use your multimeter on AC scale.

 

[Doppleganger]

Looking more like its the reman alternator. I got it at OReilly's. Had good ratings but the only real reason I got it was because I was in a bind and its 8 blocks away. Remans are such a pig in a poke. I avoid them whenever possible.

I used to rebuild Denso alternators so figured I would do this one as well. Apparently they are onto this idea as the diode pack ($35-60 on any other Denso) is $264 for this one. Crazy. Delco makes a NEW one in their gold series for about $140 which looks doable also.

On a side note......about 6 yrs ago I had an alt fail on a Volvo. Was a Bosch unit and of course, it was like 15F outside. So I bought a reman'd Bosch to get by. Their regulators are external - said "Made in West Germany". WTF? I pulled it and the brushes were gone. I swapped in a new regulator (always had a couple new ones on hand) and drove it through winter. Pulled it in Spring - put their West German regulator back in and returned it. Put a rebuilt Denso in (better alt anyways).

 

[Grit dog]

I would be suspect of a bad diode/rectifier as well. I’ve had similar (bad) luck with reman alternators. One thing I noticed (while swapping out 3 different remans in a Napa parking lot, to find a good one, is if the alternator checks out fine, the rectifier is not replaced.
Last bad alt I had was on our sons Mustang. Low miles but over 10 years old.
And it was just a bad diode causing inexplicable engine cam sensor issues (replaced both cam pos sensors even though the code thrown was always for just the one same cyl bank).
After being totally stumped the internet revealed a bad diode causing AC ripple was actually messing with the signal in the cam sensor.
Following my string of piece of junk reman alternators, had a rebuilder put a new rectifier in it and that fixed it.
The random sensor issue for me could just as easily be some other random electrical issue due to bad diode(s).

 

[Doppleganger]

Battery tested as good. Fully charged. So I think the issue was the reman'd alt. There are usually 8 diodes in these. 1 blown and it still works. 2 blown and it gets temperamental (like its been). 3 blown and the dash light stays lit, while headlights go out. I've had them with 2 down and 3 more pretty roasted and ready to go.

Still going after the new-manufactured Delco. Going to dissect an OE to see if I can find who makes the rectifier bridges.

And fwiw....the replacement reman'd alt (which is going back anyways) is putting out 14.5v but has a noisy bearing. UFB.

 

[bucket]

What I don't understand is, how can the alternator cause the brake warning light to come on?

 

[Doppleganger]

From what I have read, apparently if the ECU detects a charging issue, it disengages the anti-lock system to conserve power.

When these acted up on Volvos, it could be ANY random light (dimly lit) - something to do with a blown diode causing a back feed.

 

[Grit dog]

What I don't understand is, how can the alternator cause the brake warning light to come on?

The cornfusers in these newer fangled cars like clean clear power and all sorts of things not easily detectable to those of us who think a HEI is still a wonderment over points ignition tend to happen….
Like our 2016 Ram Diesel. It goes all to hell in weird ways with questionable batteries.
The 86 GMC, if the old reman battery had enough juice to crank the motor 3 revs, you were off to the races.

 

[bucket]

The cornfusers in these newer fangled cars like clean clear power and all sorts of things not easily detectable to those of us who think a HEI is still a wonderment over points ignition tend to happen….
Like our 2016 Ram Diesel. It goes all to hell in weird ways with questionable batteries.
The 86 GMC, if the old reman battery had enough juice to crank the motor 3 revs, you were off to the races.

Yeah I get that part of it. Newer vehicles do weird stuff with low voltage, but there's always an exact reason for the weird stuff. My question was more specific to this exact case, which Chris' research about the PCM programing pretty much answered.

 

[Snoots]

Well, you said you replaced the negative battery cable and I am NOT disputing the alternator issue but, what about the positive battery cable?

 

[Doppleganger]

Well, you said you replaced the negative battery cable and I am NOT disputing the alternator issue but, what about the positive battery cable?

I didn't replace it - just removed it from the battery terminal and cleaned it is all. Was heavily corroded.

 

[Snoots]

That corrosion will crawl into the cable and ruin it. After you get it fixed and running, grab the cable and if it's warmer than what you might expect, replace it. Welding cable works very well.