Mazda5 Electrical issues (diagnosis in progress)

[IamFODI]

Symptoms developing over the past few days (not sure if all are related):

- Mild vibration at idle
- Kenwood touchscreen's CarPlay connection unstable when engine is running and warm
- Starter cranks more slowly than it used to
- While maneuvering in a parking lot, traction control & ABS lights turn on while I'm steering and turn off when I stop steering
- While driving with AC blasting, TC & ABS lights stay on at idle but turn off above 1k RPM

Battery Voltages:
~11.3 with car off
~13.4 after cold start, engine idling
~11.5 with AC on & rad fans maxed **

** EDIT: This was only a momentary reading the moment the fans went high. I didn't wait around to see if voltage ramped back up.

Battery is barely a few months and a few thousand miles old (Odyssey AGM, oversized). Alternator may be original (MY 2012, >166k miles).

Today I pulled both battery connectors, cleaned them a bit, reconnected them with a thin layer of dielectric grease on the battery posts, cranked the nuts down nice and tight, and cleaned the ring terminal on the chassis ground up at the top of the engine bay. Haven't retested anything since then; waiting for my CTEK to top off the battery first. Will report back when I do.

What else is easy to check? And/or, does the above pattern of symptoms strongly suggest any particular problem?

 

[hleboklop]

I would check the generator, serpentine belt, and AC clutch.

 

[IamFODI]

I would check the generator, serpentine belt, and AC clutch.

Thanks.

Belt is even fresher than the battery.

Why the AC clutch? How would that affect the electricals?

 

[hleboklop]

AC clutch tends to go out and block the serpentine belt on the way out.

 

[IamFODI]

AC clutch tends to go out and block the serpentine belt on the way out.

Oh, yikes.

Wouldn't that smoke the belt in a hurry?

 

[IamFODI]

18 miles this AM after having the vehicle on the CTEK all night. No issues, as far as I could tell.

Planning to keep the vehicle on the CTEK while it's at home until I can replace the alternator (preventatively if nothing else). Will have the alternator tested at some point and post back if I find anything new. In the meantime, appreciate any further thoughts.

 

[edmaz]

Symptoms developing over the past few days (not sure if all are related):

- Mild vibration at idle
- Kenwood touchscreen's CarPlay connection unstable when engine is running and warm
- While maneuvering in a parking lot, traction control & ABS lights turn on while I'm steering and turn off when I stop steering ....

Does the above group of symptoms happening only with AC on, or do some or all of them also show up with the AC off?

Battery Voltages:
~11.3 with car off ..

You wrote that it's turning over slower, but I'm surprised it even turns over at all with that voltage reading.

~13.4 after cold start, engine idling ....

That's a normal/typical running voltage, and suggests (but does not guarantee) a properly functioning alternator.

~11.5 with AC on & rad fans maxed ...

I'm assuming that's not just a momentary voltage drop, and does not almost immediately bounce back up to 13+V. If so, that's a huge and highly abnormal voltage drop.

Naturally I have no idea what specific testing you've done, but I'd be most interested in what happens if the vehicle is driven with the AC never turned on. If you haven't already done so, try a test drive of at least 20 minutest with the AC always off, and check the voltage reading a few times along the way. Then, if the voltage during that test drive always stays over 13V, let the vehicle idle until the coolant temp goes high enough to trigger the fans to start running. Check the voltage when the fans cycle on and off , and also while they're running. Depending on the results of all of that activity, you would move on to the next set of testing.

 

[IamFODI]

Thanks, @edmaz.

Does the above group of symptoms happening only with AC on, or do some or all of them also show up with the AC off?

Only noticed it with AC on. But I suspect that's a coincidence given that AC also triggers the main cooling fan. Even with AC on, I don't think anything went wrong until the main rad fan cranked up to high speed.

Could the alternator be good enough to run the car with moderate-to-low electrical load, but unable to deliver significantly more current than that? I feel like that's consistent with what I've observed, but I'm not an expert.

 

[edmaz]

Thanks, @edmaz.


Only noticed it with AC on. But I suspect that's a coincidence given that AC also triggers the main cooling fan. Even with AC on, I don't think anything went wrong until the main rad fan cranked up to high speed.

Could the alternator be good enough to run the car with moderate-to-low electrical load, but unable to deliver significantly more current than that? I feel like that's consistent with what I've observed, but I'm not an expert.

I believe the type of testing that I described in my previous post could supply some good information about what's going on with your vehicle. The idea is to take the AC out of the mix and see what the result of that is. If the voltage always holds steady above 13V with the AC off and the fans running, then you would start turning on the other electricals (except the AC), and see what the effect on the voltage is with everything else running.

But if the voltage does take the same type of big drop that you posted with the AC off, then you take the fans out of the mix, and try turning everything else electrical on without the fans running.

Also, you're certain the new serp belt is properly tensioned, correct?

 

[IamFODI]

Also, you're certain the new serp belt is properly tensioned, correct?

Was done at a dealership, so... no. It's an auto tensioner, though, right? I'm not getting any squealing or smoking AFAICT...

 

[IamFODI]

So Sunday night, I had neglected to connect the CTEK. Checked the battery in the AM and it was right at 12.67 V. Drove it that day, let it sit overnight without the CTEK again, and checked the battery again the following morning. 12.67 V again. No other signs of trouble, and I haven't been shy about electrical load. Been driving a lot with max AC to get the interior as cold as possible so that, when I park it and come back, it won't be as ridiculously hot. Zero issues.

Still planning to do some more testing at some point when I have more time. Will also probably replace the alternator preventatively before winter. Even if it's in good enough shape, it's gotta be at least a little tired by now, right? And we have at least one road trip planned.

For now, though, she seems fine. Fingers crossed!

 

[negusm]

Sounds like you have a drain somewhere.

If it happens again, disconnect ALL aftermarket devices.

I have ripped out countless aftermarket junk out of cars and electrical problems always evaporate.

 

[IamFODI]

So, some background info I had omitted: The car sat for a little over 2 weeks while I was out of town. It had a bit of work done and then drove for 30-40 mins, mostly highway, before sitting for another 10 days or so. No issues on that drive, or on the ~55 min drive home – except for the idle vibration.

The other symptoms developed over the following couple of days. Then they all vanished after I had the car on the CTEK long enough, and they haven't come back since.

I'm thinking either

1. The terminal connections were wonky somehow and my fiddling fixed them, or
2. The battery got low enough while the car sat that the alternator couldn't charge it properly, and the battery just net-depleted instead...? Is that a thing?

#ShrugLife

 

[Silentnoise713]

The car sat for a little over 2 weeks while I was out of town. It had a bit of work done and then drove for 30-40 mins, mostly highway, before sitting for another 10 days or so.

I think this is it. I don’t have much experience with AGM batteries but my understanding in is that when they are fully deeply depleted, they need slow trickle charge for 24-48 hrs before use. 2weeks + 10 days with only 30-40 min alternator recharge is likely not enough. Also AGM batterie should not be depleted down to less than 50% charge (should have disconnected it). I wouldn’t blindly replace the alternator just yet as I don’t find that to be a common issue on this car.

 

[IamFODI]

After sitting for 3.5 days, battery voltage is at 12.5. Normal?

 

[Silentnoise713]

google iamge "normal battery voltage" to get a perspective. You should get a 2nd datapoint to get a trend. If possible, leave it for another 3.5 days and check again to get a better gauge of your parasitic drain.

 

[IamFODI]

google iamge "normal battery voltage" to get a perspective. You should get a 2nd datapoint to get a trend. If possible, leave it for another 3.5 days and check again to get a better gauge of your parasitic drain.

Wow. According to this, my battery was practically dead when I posted this thread!

https://static.cargurus.com/images/site/2015/10/12/17/05/pic-1135060123859808935-1600x1200.jpeg

 

[Silentnoise713]

That is a lead acid battery chart. You need to look up AGM battery (it's not any better).

 

[IamFODI]

Several days later, driving almost every day (including some short trips), everything's cherry. Zero issues.

Alternator's gotta be at least a little tired after 11 years and 167k miles, right? But I guess it's fine, or I'd have had problems again by now. Same with the other electricals, right? Someone correct me if I'm wrong on any of that.