I've had some quirky "Low Power Mode" things happen when I first start the vehicle, and sometimes just restarting it solves the problem - so I know how random it can be, but this morning something different happened that has me thinking (this time at least) it might be pointing more towards a potential issue?

Just sitting in traffic - vehicle was running for probably 20 minutes already (started perfectly this morning, drove normally) I'm sitting at a light, headlights on, fog lights on, heater on, radio on but no heated seats or heated windshield, compressor not running... so fairly normal electrical loads.

Then I noticed my music volume reduce slightly and sure enough when I tried to go above 20 again it said "Low Power Mode".

I got a little concerned thinking my alternator took a crap and I may be running on battery soon, so turned off everything I didn't need.. stoplight turned green and I drove off.. 2 minutes later I tried again and had full volume control once more.

So the vehicle DID see something it didn't like. I know they don't generate as much current at idle, but its' capacity should still have TONS of headroom.

There doesn't seem to be documentation on the low power mode thing. I have read the documentation on the variable load/charge distribution system and the radio/amp is something it can "throttle" - maybe it's safe to say that when the system limits radio current, it displays that message to let you know.



Tuesday when I had the passenger heat shields and wheel off after starter install, I started it up to test install - noticed how LOUD the alternator was on a cold start with the compressor running. Whining noise went away by about 70% when the compressor shut off.

Is it safe to say these are fairly decent hints that my alternator is near the end of its life? Vehicle has just under 108k on it.

We have a new Autel scanner - wonder if it can show load current vs. charge current? I guess I would need some kind of reference for power vs. rpm though. Does anyone know what module that would be under?

I just really don't want to get into a situation where I'm stranded, have a smoking alternator, shorts my battery out when parked at night... the failure modes of these things tend to be BAD stories lol.

edit: Obviously the battery light never came on, that's more indicative of a complete failure though. Which I'm trying to avoid. Just thought I'd add that!

edit 2: At least my thought process is correct - just looking at UK forums, one guy got that message at highway speeds and 10 min later vehicle shut off on him! I guess 800rpm is very different than 1800rpm, but doesn't sound good for my alternator. Apparently the battery light is a crappy indicator of failure (ironically) sometimes.

 

How old is the battery?

Agree on the highly destructive failure modes of the alternators on these, makes me worry as well.

 

Basically brand new Interstate MTP H8, maybe 5 months.

For some reason I thought replacing the alternators on these was a PITA (due to its location on the bottom AND how much fun I had doing the starter the other day) but apparently once you get that cover off next to frame/tie rod, you pretty much have direct access.

 

I had a similar issue maybe a year ago... and for the life of me I can't figure out what caused or solved it. It went away after a few times.

I think my battery was low-charged from sitting for a month and a half in the VA heat. Did the alternator change remedy this for you?

 

Tuesday was the starter replacement - and yup, been perfect ever since - even on these colder mornings (when I had about a 5% start rate on old one lol). I've gotta upload pics of the solenoid contacts, they were totally cooked.

From what I've read I need to bite the bullet on this thing. There's an older thread on another forum asking about life span and failure mode, and once they start the "cold / first start morning whine" most people had 2-10 months before they died completely. Mine probably REALLY started making that noise about 3 months ago. Most also mentioned the "low power mode" during that same time.

Meh.

 

So it was starter AND alternator or just one of those?

Hmm gets me thinking. That was at least 8 months back...

 

Nah sorry for the confusion. When I was doing the starter on Tuesday I had all the heat shields off and when I tested the starter and crawled down by the front pass wheel area I realized how LOUD the alternator was till the compressor load was removed and it became a little more normal.

This morning the "low power mode" thing happened in traffic, so I made the thread about the alternator.

When starting the car the scanner showed 14.44 and came down to about 14.01 15 minutes later which seems normal as it finishes slight recharge and loads drop off a bit.

 

HAH! Guess what just took a crap on me during my evening commute?!#%



Sucks that I've gotta buy the part / swap it out, but I'm kinda thrilled that I knew EXACTLY what was happening even though my car gave zero clues during the real failure.

About 15 minutes into stop-go traffic (first "hot" day at about 86 degrees, I had my front and rear HVAC on high AC) I noticed a slight rpm-dependent noise that wasn't there before. I thought it was just my AC compressor getting louder since I hadn't used it in a while.

Pressed the econ button and the noise stayed the same. Very loud from 1100rpm and under (as I'd decel to a stop). Same general area-ish as the alternator whine I had observed in the past.. so I was a little worried. Shut off the radio, and all HVAC, lights, gps screen, etc.. I had put my windows down to listen to the noise, and at the next stop in traffic, I noticed a faint hint of "burning electronics smell".

No way this was actually happening in such a predictable way.. right?

So I make it another 30 min to my indy shop (keeping an eye on the dash in case the battery/alt light came on) I needed gas anyways, and I figured if my batt was dead now and it wouldn't start again, it would be a perfect place to leave it.

Well it fired right up - I listened down by the pass wheel and noise/smell was right down there. Pos batt cables were hot(er than usual/normal). I took the batt cover off and decided to make a run for home.

Got home with no problems - no warning lights, still the loud rpm noise under 1100 and burning smell.

I grabbed a volt meter.. 12.55v off. Fired it up and checked... 12.40v!!!!! I turned on some loads and both HVAC again, and got the thing down to 12.02v, NO BATTERY WARNING LIGHTS ON THE DASH!

I had heard (and mentioned above in this thread I think) that others reported alt failures with no warnings. Now I know. I'm guessing whatever component in the voltage regulator that reports good charging gets fried when they fail - obviously defeating the purpose. Combine that with the fact that they latch into a direct short when people park them, and this has got to be the worst designed alternator I've ever seen.

Anyways during the drive it was doing exactly what I was worried about in the back of my mind.. basically ran on battery for ~45 minutes. I was still shocked to see that volt meter reading that confirmed it.

Disconnected the battery (to avoid the direct short that happens apparently) and put it on my pulsetech charger. I'll have to fire up the disco and take it to work tomorrow (first time in about 8mo) and bring a new alt. home. I guess no battery damage, no towing, and no shop costs, AND no batt/alt warning light is a pretty decent accomplishment for enduring an alternator failure.

I just wanted to let everyone know that if you're "in tune" with your vehicle close enough, you can gather enough info to avoid being stranded most of the time and preempt many failures (I almost replaced it when I made this thread!) - this is definitely proof of such a situation, though I can think of a ton off the top of my head.

Also, these alternators definitely do have specific signature failure modes that are fairly unusual, and rather dramatic.

It's also interesting to note that when my starter became unusable (the click/nostart issue) the alternator began failure symptoms within a few days of that about a month ago. I'm sure it's mostly coincidence, but windings, bearings, and conductors are probably engineered for a target lifetime - I guess 108k miles on an alternator isn't really that bad at all. Just wish it had died in a semi-normal manner with warning indicators like every other vehicle in the world since the 1950's!

 

Wow..My alternator still going strong at 187 000 miles, I guess mine is not average ,so is air compressor.

 

Did you buy the vehicle new? There's a thread somewhere about how / when everyones alternators died and they were all around 65-110 with a sweet spot around 85-95 it seemed like. I'd imagine you'd have to be on your second unit - the regulators inside these things just don't seem capable of "miracles" based on their dramatic failure modes.