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Old 08-13-2015, 08:21 PM   #1
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Default Electrical/system voltage issues?

So lately (as of Monday) had some kind of an issue that I'm guessing is related to the batt/alternator system. Long story short, I've noticed that speakers cutting out randomly while driving. At first, it just happened mostly when holding a steady speed with light throttle adjustments. Now, it happens when accel/decel, on brakes, off brakes and even sitting still. I suspect it's not a wire or the stock Bose headunit, but suspect erratic voltage in the system.

I thought I could datalog voltage, but apparently I have to pay for that feature lol. But with the laptop on while on a short trip, I watched voltage dither very quickly between 13.7v-14.3v. Turning on lights/hitting brakes/blasting the blower motor/coolant fans cycling and even hitting the hazards didn't cause the voltage range to move or act any differently.....but it did cause my idle to dip quite a bit when sitting still. I cannot say I've ever had this kind of a problem and am looking for some insight before throwing parts at the car.

Anyone ever had a similar issue?
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Old 08-13-2015, 08:55 PM   #2
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<p>You have a Hydra right? It does alternator control?</p>
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Old 08-14-2015, 01:05 PM   #3
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So if the alternator is changing output because of age/wear, I can tweak the map to compensate for that? Would it not be better to replace the alt.?
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Old 08-15-2015, 01:06 AM   #4
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Compare the target voltage to the actual voltage and report back.
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Old 08-15-2015, 05:18 AM   #5
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Will do.
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Old 08-15-2015, 01:14 PM   #6
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Your alternator is fine, from the details you've given.

Speaker cutting out has zilch to do with an alternator.
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Old 08-15-2015, 06:05 PM   #7
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Have any ideas? Another thing I noticed were my AFRs jumping around like crazy..IIRC they shouldn't be jumping around that quickly and def. not the sign of a bad WB (been through that a couple of times). I would log the system voltage, but I think I have to pay to unlock that feature


Here is a short sample of the AFRs from the datalog I just took...this was at idle...

0.000s 15.7afr
0.083s 16.3afr
0.167s 16.5afr
0.250s 13.5afr
0.333s 14.6afr
0.417s 16.6afr
0.500s 13.1afr
0.583s 14.3afr
0.667s 15.0afr
0.750s 14.3afr
0.833s 13.2afr
0.917s 14.6afr
1.000s 14.1afr
1.083s 15.4afr
1.167s 18.5afr
1.250s 15.7afr
1.333s 13.8afr
1.417s 14.6afr
1.500s 16.8afr
1.583s 15.7afr
1.667s 15.1afr
1.750s 16.3afr
1.833s 15.3afr
1.917s 15.9afr
2.000s 14.1afr
2.083s 15.9afr
2.167s 14.0afr
2.250s 13.7afr
2.333s 14.6afr
2.417s 15.9afr
2.500s 14.6afr
2.583s 13.7afr
2.667s 14.4afr


So jumping AFRs, jumping battery voltage...bah...it just seems to me that there is instability in the system somewhere and the root of the system when the car is running is the alternator.
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Old 08-15-2015, 06:20 PM   #8
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Or a bad ground somewhere
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Old 08-15-2015, 07:35 PM   #9
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If anything I'd say your voltage compensation or alt control is off, but if an alt it'll either be no voltage or too high of voltage. Electronically, those are the only ways they'll fail.
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Old 08-15-2015, 10:41 PM   #10
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Quote:
Originally Posted by olderguy View Post
Or a bad ground somewhere
This. My money is on a loose ground.
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Old 08-16-2015, 01:33 AM   #11
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Any particular ones that can be an issue? My understanding of that would be that energy not being grounded would make that circuit run high. But ive made observations of the battery's voltage running low and not going up (see below)....only confusing me further...

Curly- Good to know that...cant say I did and that helps my view of what's going on.

Hooking up the laptop to the car without it running did show batt. voltage at 11.2v. Cranked the car up and it just went back to doing what it's been doing. After a 30min drive, I had the car idiling and just for fun I turned on the lights, blower at full, hit the brakes and activated the hazards and I saw the batt voltage drop to ~11v with it dithering from 10.8 to 11.4 and didn't go up for the minute or so I did that. Bad battery afterall? That was the last thing I did before stepping away from the car.

I can't say electronics are my strong point...so is it logical to see where I'm thinking based on seeing these values jumping around and the radio cutting out suddenly? I can't say I understand the issues a bad ground would cause as I've never had to deal/troubleshoot such an issue.

Last edited by Doppelgänger; 08-16-2015 at 02:05 AM.
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Old 08-16-2015, 02:23 AM   #12
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Any ground could be the issue. Easiest way to find/check is go get out a multimeter.

Start engine, let it idle.

Measure voltage between engine block and alternator post. Record it.

Check voltage at battery terminals, record it. Also check between battery + terminal and chassis nearby battery, record it.

Check voltage at fuse panel and chassis, record it.

Check voltage between engine block and car body/chassis, record it.

Check voltage between alternator post and fuse panel, record it.

Post results and I'll let you know if anything looks wrong or if it looks ok.

In short, the multimeter shows you the voltage DIFFERENCE between whatever two things you touch.

So if you put one on the engine block, and one of the chassis, and you see 1.0V, your engine block is very poorly grounded. These should show 0.00 to 0.02 volts when the car is idling since they are electrically connected together via the ground wire in the rear of the car near the battery. And in the engine bay too near the exhaust manifold/firewall area.
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Old 08-16-2015, 12:28 PM   #13
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Where does the Hydra pick up the Kelvin sense?
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Old 08-16-2015, 12:42 PM   #14
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Thank you, Pat.

Sorry if I come across at being hard-headed or argumentative....I just don't care for the added stress of this issue on top of a lot of other things right now, as well as would really like to have someone in the garage helping me with this crap :/
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Old 08-16-2015, 01:04 PM   #15
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It would really help if you could post a datalog where we could see the voltage.

I know you wanted to stay with the Hydra, but like many people have said, the forum knoww the Megasquirt on our cars inside-out, so it would have literally taken just seconds to find out if it's really an issue or not.
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Old 08-16-2015, 01:23 PM   #16
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I actually have a log from yesterday, but you know, Hydra format...so here it is in .csv





I dunno....I question my ability to care about this "hobby"....I'm fighting pretty hard just to do the simple things like changing oil and brake pads...
Attached Files
File Type: csv run with 3deg pulled over 100kpa csv.csv (287.3 KB, 37 views)
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Old 08-16-2015, 01:55 PM   #17
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I scrolled through the file on my phone, so I may have missed something, but the battery voltage appears to be fairly well regulated.
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Old 08-16-2015, 01:57 PM   #18
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It does look like the voltage is not controlled well, but not to the extent that speakers would be cutting out.

Amp/head unit?
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Old 08-16-2015, 02:05 PM   #19
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OE Bose.
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Old 08-16-2015, 02:32 PM   #20
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Yeah, what I meant to ask is "maybe the head unit/amp is on it's way out"?
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