Inconsistent voltage, causing ALP errors

Deacon

TXCTG
VIP
Lifetime Premium
Advanced User
Joined
Nov 13, 2016
Messages
16,156
Reaction score
23,573
Location
Hill Country, TX
I think @benzr is onto something. It may be functioning as intended, it’s just that aftermarket accessories aren’t expecting it.

What you can do, if you like, is to run a hot wire through the firewall (probably just alongside your existing ALP cables) directly to the positive terminal of the battery, fused very near the terminal, from near wherever your power source is now behind the dash. Use that to power your R7 and ALP instead of your fuse tap or whatever it is now. If you have a 12V switch handy, even better to make it a little smoother to turn off and on rather than literally being always hot. Go take a drive and keep an eye on the voltages.

If everything looks like you’d actually expect, no weird dips or errors, then maybe just wire up a cheap relay to trigger off the accessory switched power you’ve been using. That way the R7 and ALP get power straight from the battery, no weird games played by the ECM.
 

STS-134

Premium Plus
Lifetime Premium
Advanced User
Joined
Mar 6, 2014
Messages
12,788
Reaction score
14,534
Location
Saratoga, CA
I think @benzr is onto something. It may be functioning as intended, it’s just that aftermarket accessories aren’t expecting it.

What you can do, if you like, is to run a hot wire through the firewall (probably just alongside your existing ALP cables) directly to the positive terminal of the battery, fused very near the terminal, from near wherever your power source is now behind the dash. Use that to power your R7 and ALP instead of your fuse tap or whatever it is now. If you have a 12V switch handy, even better to make it a little smoother to turn off and on rather than literally being always hot. Go take a drive and keep an eye on the voltages.

If everything looks like you’d actually expect, no weird dips or errors, then maybe just wire up a cheap relay to trigger off the accessory switched power you’ve been using. That way the R7 and ALP get power straight from the battery, no weird games played by the ECM.
But that doesn't explain why it operated without trouble for many months. Something is wrong with his car, and I suspect it's some sort of voltage regulator. I think alternators typically have electromagnets in the rotor, and are supposed to regulate the voltage at the output, and make it more or less independent of engine speed, by controlling the strength of those electromagnets.

Here's my guess:
  • The dead battery is a symptom, not the root cause
  • The alternator's voltage regulation system is messed up such that it doesn't produce enough voltage at high speeds but does produce some barely adequate voltage at low speeds (enough to run the electronics but not really enough to charge the battery)
  • The amount of current sent to the electromagnets in the rotor is too low especially when the alternator spins up, causing inadequate induced voltage in the stator
  • This in turn causes the battery to be kept at a low state of charge and that's why it died when the car was sitting at the airport
Remember, you should be seeing 14.2V or more when the engine is running. If you're below float voltage (13.6V) then something is wrong. Some dips are expected if the engine speed is low and you're running a lot of load but this shouldn't happen when the engine is spinning fast.
 
Last edited:

benzr

Been there done that !! Original V1 user !!
Advanced User
Joined
Apr 23, 2012
Messages
6,634
Reaction score
10,080
Location
FLA
But that doesn't explain why it operated without trouble for many months. Something is wrong with his car, and I suspect it's some sort of voltage regulator. I think alternators typically have electromagnets in the rotor, and are supposed to regulate the voltage at the output, and make it more or less independent of engine speed, by controlling the strength of those electromagnets.

Here's my guess:
  • The dead battery is a symptom, not the root cause
  • The alternator's voltage regulation system is messed up such that it doesn't produce enough voltage at high speeds but does produce some barely adequate voltage at low speeds (enough to run the electronics but not really enough to charge the battery)
  • The amount of current sent to the electromagnets in the rotor is too low especially when the alternator spins up, causing inadequate induced voltage in the stator
  • This in turn causes the battery to be kept at a low state of charge and that's why it died when the car was sitting at the airport
Remember, you should be seeing 14.2V or more when the engine is running. If you're below float voltage (13.6V) then something is wrong. Some dips are expected if the engine speed is low and you're running a lot of load but this shouldn't happen when the engine is spinning fast.
He has the same issue my Jeep ECM Regulator
Had.

Just charge your batt overnight.
You can get a trickle 12v charger, but it is not necessay.

See ALTERNATORS do NOT CHARGE ... they alternate the current (why you can run ac power off your alternator) so your batt if run down a lot by leaving a glove box light on (usual suspect) or left lights on once or traffic didnt give the batt enough juice to alternate THE BATTERY WILL STAY PARTIALLY CHARGED 🤔🤔😳😳

Therefore, the ELD will slways be trying to catch up.

On my jeep i charged the battery overnight and
Low Voltage warnings on my Detectors stopped.

Summary:

Batt went partial charged once by whatever
ELD is struggling to match the requirements it "thinks" it needs.
Batt stays Low so tolerances are off on the ELD
Telling alternator thru its fields NOT to add volts

So TRY TO CHARGE BATT OVERNIGHT. 👍👍😎😎

Benzr
Post automatically merged:

But that doesn't explain why it operated without trouble for many months. Something is wrong with his car, and I suspect it's some sort of voltage regulator. I think alternators typically have electromagnets in the rotor, and are supposed to regulate the voltage at the output, and make it more or less independent of engine speed, by controlling the strength of those electromagnets.

Here's my guess:
  • The dead battery is a symptom, not the root cause
  • The alternator's voltage regulation system is messed up such that it doesn't produce enough voltage at high speeds but does produce some barely adequate voltage at low speeds (enough to run the electronics but not really enough to charge the battery)
  • The amount of current sent to the electromagnets in the rotor is too low especially when the alternator spins up, causing inadequate induced voltage in the stator
  • This in turn causes the battery to be kept at a low state of charge and that's why it died when the car was sitting at the airport
Remember, you should be seeing 14.2V or more when the engine is running. If you're below float voltage (13.6V) then something is wrong. Some dips are expected if the engine speed is low and you're running a lot of load but this shouldn't happen when the engine is spinning fast.
You're on the right track BUT he has yhe ELD system (computer Regulator)

Expand my pics and you'll see how his Alternator and charging system function.
It's on Civicforums.com.

B
 
Last edited:

Saussie

PSL +5
Intermediate User
Joined
May 8, 2018
Messages
1,135
Reaction score
746
Location
The middle of nowhere
Could give the nuts on the alternator a tighten up. Check the wires have good contact, and no corrosion or oily crap getting under the contacts. Clean them and bolt them down again. Scratch some fresh metal away and make sure it's contacting well.
I have a car here that flashes the battery light on and off as I'm driving it and I suspect a wire. I've repossessed this car though from someone stuck overseas at the moment. Long story but an agreement for parking expired, and they've been leading me on a little. So I served them a notice for someone to come and get it, and it's turning out and looking like I get to keep the car by the looks, as much as I don't want it. It's battered and needs to go to the wreckers, 2 bald tyres (I should finish them off with a fat burnout) and the elec gremlins on it arn't worth the time and effort for the cars value. Looking forward to scrapping the catalytic for $$ and dumping it to gain some more parking space.
 
Last edited:

Jon at Radenso

Manufacturer
Lifetime Premium
Corgi Lovers
Advanced User
Manufacturer
Joined
Oct 9, 2012
Messages
3,487
Reaction score
29,069
Age
32
ALP is fairly intolerant to low voltages. I believe it's about 11.5 or 11.6v where it will start throwing errors. It's not common for us to run into this, but it's not uncommon either. The RC M will tolerate lower voltage than ALP, so it's an issue that confuses our dealers sometimes when the radar is working but the ALP is throwing errors.

Also, you can't really trust voltage readouts on most detectors. I know the one on our Pro M can be woefully off. I would check with a multimeter and I bet you're dipping into the 11.6v range occasionally which would cause the issue.
 

Deacon

TXCTG
VIP
Lifetime Premium
Advanced User
Joined
Nov 13, 2016
Messages
16,156
Reaction score
23,573
Location
Hill Country, TX
But that doesn't explain why it operated without trouble for many months. Something is wrong with his car, and I suspect it's some sort of voltage regulator.
Certainly it could be that, or it could be something else, even his perception of how often he notifies the grating warning. Running a wire to the battery eliminates many of the questions by bypassing all the complexities.

So TRY TO CHARGE BATT OVERNIGHT.
He said he installed a brand new battery already.
 

benzr

Been there done that !! Original V1 user !!
Advanced User
Joined
Apr 23, 2012
Messages
6,634
Reaction score
10,080
Location
FLA
Certainly it could be that, or it could be something else, even his perception of how often he notifies the grating warning. Running a wire to the battery eliminates many of the questions by bypassing all the complexities.


He said he installed a brand new battery already.
Um ... I missed that. 😳🤔🤨😳

Then your Direct wire Solution seems to be the solution.

@ARkaband
Try @Deacon's solution w a temp wire 🤓🤓

Benzr
 

STS-134

Premium Plus
Lifetime Premium
Advanced User
Joined
Mar 6, 2014
Messages
12,788
Reaction score
14,534
Location
Saratoga, CA
Certainly it could be that, or it could be something else, even his perception of how often he notifies the grating warning. Running a wire to the battery eliminates many of the questions by bypassing all the complexities.
...and shouldn't be necessary, and even worse, leaves the problem in place. The failing ALP is like the canary in the coal mine and all you've done is given it a gas mask.
 

Deacon

TXCTG
VIP
Lifetime Premium
Advanced User
Joined
Nov 13, 2016
Messages
16,156
Reaction score
23,573
Location
Hill Country, TX
The failing ALP is like the canary in the coal mine and all you've done is given it a gas mask.
I understand that you feel very strongly about this, but I disagree. It’s a diagnosis tool that could turn out to be a long term option.
 

STS-134

Premium Plus
Lifetime Premium
Advanced User
Joined
Mar 6, 2014
Messages
12,788
Reaction score
14,534
Location
Saratoga, CA
I understand that you feel very strongly about this, but I disagree. It’s a diagnosis tool that could turn out to be a long term option.
Rather than pulling a wire through the firewall, it's far easier to put a voltmeter on the battery terminals and on the car's 12V outlet and see if there's a difference at various engine RPMs. The ALP will only tell you if voltage gets excessively low (like below 12.0V) but there's a major problem if the battery isn't seeing at least 14.2V.
 

Deacon

TXCTG
VIP
Lifetime Premium
Advanced User
Joined
Nov 13, 2016
Messages
16,156
Reaction score
23,573
Location
Hill Country, TX
Rather than pulling a wire through the firewall, it's far easier to put a voltmeter on the battery terminals and on the car's 12V outlet and see if there's a difference at various engine RPMs.
He's already got wires pulled through the firewall in general, so depending on how it's been done it may be quite simple to pull another one. Putting a multimeter on the battery in a way that you can test without a helper is certainly possible, assuming he's got the right equipment to do so, but even then there's some question regarding no-load RPM. The nice thing about running a wire through the firewall is not only do you have a great option for powering devices moving forward, but real-world monitoring directly to the battery under driving conditions becomes possible--and the voltage detected by ALP and the R7 can be checked against a multimeter while underway.

The ALP will only tell you if voltage gets excessively low (like below 12.0V) but there's a major problem if the battery isn't seeing at least 14.2V.
The voltage reaching the ALP and R7 may not be directly tied to what the battery is seeing, presuming they're being powered off some managed vehicle circuit. You're right, of course, that the battery should be seeing 13.5V to 14.5V from the alternator under normal conditions.
 

Fireball

Learning to Fly
Beginner User
Joined
May 17, 2020
Messages
561
Reaction score
756
I know nothing about Hondas, so I used my :ninja: Duck Style :ninja: to come up with this.


Very nice writeup on how your charging system works, and what you can check to try and resolve the issue.
 

Saussie

PSL +5
Intermediate User
Joined
May 8, 2018
Messages
1,135
Reaction score
746
Location
The middle of nowhere
Had a Honda Civic once. Kinda miss that car. It had lots of legroom for a hatchback. I'd have to rev the hell out of it to get it going but it flew along nicely. Never dropped a dot of oil. Solid car. Only Honda I've messed about with. NSX would be cool.
 

oktavf

Premium Plus
Lifetime Premium
Advanced User
Joined
Nov 20, 2017
Messages
1,497
Reaction score
2,068
Location
NW GA
Yep alternator or even bad/dirty battery terminals. Could also be a bad/loose ground wire on the block etc. I once had a regulator diode short if I recall many moons ago and it would constantly drain the battery even with the car off through the alternator lol that was a fun one. Also get one of those cig lighter voltage gauges that are usually USB chargers as the Uniden built in one is iffy at times unlike those. I even have one in my company car I hate surprises! :p

That's dumb...
 
Last edited:

ARkaband

War Eagle
Premium Plus
Lifetime Premium
Corgi Lovers
Advanced User
Joined
Jul 28, 2019
Messages
2,045
Reaction score
8,722
Location
Auburn, AL
Yep alternator or even bad/dirty battery terminals. Could also be a bad/loose ground wire on the block etc. I once had a regulator diode short if I recall many moons ago and it would constantly drain the battery even with the car off through the alternator lol that was a fun one. Also get one of those cig lighter voltage gauges that are usually USB chargers as the Uniden built in one is iffy at times unlike those. I even have one in my company car I hate surprises! :p

That's dumb...
The weird thing is I never got any errors from the car. No lights or messages. Anyway, the issue persisted until I sold the car a month ago or so.
 

oktavf

Premium Plus
Lifetime Premium
Advanced User
Joined
Nov 20, 2017
Messages
1,497
Reaction score
2,068
Location
NW GA
The weird thing is I never got any errors from the car. No lights or messages. Anyway, the issue persisted until I sold the car a month ago or so.
Those idiot lights aren't always reliable. Glad you got it sorted by selling the car! 😆
 

TominVirginia

Learning to Fly
Lifetime Premium
Beginner User
Joined
May 23, 2017
Messages
187
Reaction score
461
Location
Virginia
Perfect timing for this issue and my current circumstance. Hope you don't mind me jumping in here but it sounds like there is a fairly good knowledge base and I don't trust what the dealer told me.

I have a 2018 GMC Sierra Denali. I have owned it from late 2019. The voltage gauge always read somewhere just below or just above 14v.

About a month and a half ago it started to drop to as low as 12.3-12.5v. Sometimes stay there sometimes jump back up on its own. I had the battery tested and it had lost a step in holding charge. I expect that for a OEM battery that is 50-48 months old. Replaced the battery. Same thing happened.

Pulled the alternator took it to three parts stores to get it tested. They all said the same thing that they did not have the connector to test it with on their machine. I found that weird since the its 4 years old. I guess they don't update those machines much.

Read a bunch of Chevy forums with many claiming the computer in the truck tells the alternator how much voltage to put out based on load. OK I accept that to a point but I am still skeptical. I can be rolling down the highway, lights, cooled seats, A/C, wipers etc all on and the voltage can go from 14v to 12.3v-12.8v and stay there. (I have a phone charger with a meter on it and I had a ProM both read very close to the dash gauge reading and all read the same).

If I pull over after running that way for a while turn off the truck then turn it back on it jumps to 14.5 to as much at 15v at times. That tells me the computer senses that the battery has been starved and it needs to charge it.

The dealer said all is good, no codes no issues found. The truck is under the bumper to bumper so if they found an issue they would have replaced the alternator or what ever they found defective. They did not replace it. At least they did not charge me for the diagnosis. Its still happening this week.

I don't want to get stuck on a winter night when I go out to the car and find it dead.

I am thinking just go ahead and replace the alternator and see what happens. What do you all think?
 

Millwright99

Learning to Fly
Beginner User
Joined
Aug 2, 2021
Messages
197
Reaction score
260
I agree it sounds like voltage regulator or electric load detector...
 

Deacon

TXCTG
VIP
Lifetime Premium
Advanced User
Joined
Nov 13, 2016
Messages
16,156
Reaction score
23,573
Location
Hill Country, TX
I am thinking just go ahead and replace the alternator and see what happens.
You could, but I’d really want the dealership to keep it and run it and figure it out. On my Ford, it will vary, but that variance is only whether it’s 14.2V at the beginning of a road trip to 13.8V at the end. It should never ever be at battery voltage when it’s running. Period.

The only way to be 100% sure is to actually run a wire from the battery terminals to a reliable gauge you can monitor. I can’t imagine any vehicle systems running like that, though, for any reason ever. Even stuff going through the computer fed systems like the stereo system should t be reading less than 13.5V when underway.

If you want to pay your own money, you can do what you want, but I’d want the dealer to explain to my why the alternator not charging the battery is OK and to fight for a replacement under warranty. It sounds like you already took it off yourself and put it back on, so you’ve dumped more time into than I would’ve. I wouldn’t trust it at all.
 

Discord Server

Latest threads

Latest posts

Forum statistics

Threads
99,912
Messages
1,516,660
Members
25,409
Latest member
TheDude
Top