Need some electrical advice - SOLVED

[lewma]

All

Did the tow of shame tonight. Stranded 10 miles from home but got great service from AAA and a great driver that got my MK4 on and off the flatbed without any issues.

I have a Gen2 Coyote with an Optima Red Top battery. Been running fine for the past 3200 miles. Zero issues.

Accidentally left the ignition in the On position one night last week. Discovered this the next morning and threw the battery on the optima charger I have.

Went for a drive today. 40mins into the drive, car is feeling different and its starting to loose power. Didnt look at the volts reading at that point. Couple of hundred yards down the road I pull over because car is feeling worse.

I then discover that my volts reading is 10v. Called AAA and the came and jump started me. Drove about a mile then I noticed the volts dropping down to 8v. Its backfiring, running very rough so I pulled over then got it towed home.

If anyone could lend some advice with my questions, that would be great!

- Can leaving the ignition in the ON position damage anything ?
- I'm assuming that the alternator is bad. Once the battery has enough charge, I;m going to start it then measure voltage across the battery. That a good way to test the alternator ?
- Are these Optima Red Top batteries easily damaged if they are ran too low ?

any help would be greatly appreciated!
mark

[Bob Cowan]

Allowing a wet or AGM battery to be run down too low will kill. I've done that before. Take the battery out. Put it on a trickle charger over night. Then take it down to Autozone (or wherever) and have it load tested.

Some Optima batteries seem to last forever. And some appear to be a bit fragile.

[lewma]

I managed to start the car and it's throwing P0620 and P0625 codes which both point to the alternator charging circuit

Put a volt meter across the battery with the engine running and I'm seeing 11.7v volts so its definitely not charging.

[edwardb]

Interesting. Haven't seen or heard anyone report alternator related DTC's. But makes sense since the standard harness has a connection to the controls in the alternator. That was my first reaction to your post. Even with a defective battery, seems it should have kept running if the alternator was working properly. The usual crate Coyote Ford Performance M-8600-M50BALT? Ouch, those aren't cheap and way to soon for it to fail. I assume you've checked the belt and tensioner to confirm that's all working OK?

[Railroad]

Sounds like the alt got fried when you charged the dead battery. You might get your alt repaired, cheaper than a new one?

[Richard Oben]

I can't tell you how many times we have had a battery issue eat an alternator. Not specifically on FFR cars but on all cars, happened to my wife's Acura, My excursion, etc.

If the battery was dead and a jump got it going, it did not fix the battery being dead just provided enough juice to start the car. The dead battery then ate the alternator. Take it off, (PIA) I would imagine, but if the volts are not 13.8 or 14.2 it is not charging. HTH, Richard.

[lewma]

Thanks all for the replies. Reading more about the Optima red top I have, that's a starter battery ( designed to get the engine running, and the alternator charging to top it off again ) and it's not really designed to be drained, so leaving the ignition on overnight probably started this chain of events. My optima charger started charging last night and now its saying the battery is good. I'm going to pull the alternator today to test the pins on it. I found this which gives some good information:

https://troubleshootmyvehicle.com/ford/4.6L-5.4L/ford-p0620-alternator-diagnostic-test-1

[lewma]

Took off the alternator this morning then took that and the battery to Oreillys for testing. Battery is good. Unfortunately alternator reported good too. That has me completely puzzled. I already ordered a new alternator so my thought is to put the new alternator in then give it all a test again. Perhaps the test done at Oreillys was a false positive result. ( sounds like covid testing :) )

[Rdone585]

Did you change the pullies? If the drive RPM of the alternator has changed then it may not be charging the battery unless the RPM are higher than you might think. Mine will not charge the batter unless the RPM are greater than 2000 RPM, but that's the way it's designed, so I don't spend a lot of time at idle, it's designed to run. If you didn't change the pullies then it should charge even at idle. While sitting, slowly rive it some gas and see if there is a change on the volt meter as you increase the RPMs. If there is then you can expect to discharge the battery at low RPMs.

[CraigS]

Are there any hidden fusible links in the harness wire coming out of the alt? Any in the fuse/relay box?

[RBachman]

A bit off topic, but may be of help to some. Leaving the key on in "run" position without the engine running will damage some electronic igniter modules. I had a bad ignition switch burn up a $100 module on a Petronix distributer when it was left on. Another possible concern is the battery itself. Optima batteries have developed a less than stellar reputation. I had to yank mine due to premature failure when it wouldn't properly take/hold a charge. Others have expressed issues with these batteries also.

[mike223]

I can't tell you how many times we have had a battery issue eat an alternator. Not specifically on FFR cars but on all cars, happened to my wife's Acura, My excursion, etc.

If the battery was dead and a jump got it going, it did not fix the battery being dead just provided enough juice to start the car. The dead battery then ate the alternator. Take it off, (PIA) I would imagine, but if the volts are not 13.8 or 14.2 it is not charging. HTH, Richard.

This is all exactly correct - I've had the same experience for years.


A few more notes:

I picked up excellent advice from a Minn Kota trolling motor manual years ago - never let a battery sit in a discharged state for more than 12 hours - the battery will be nothing but trouble after that.

On boats, I've typically run outboard motors that only have a 6 amp alternator - you can literally see the voltage rise once the battery is fully recharged if you're watching for it - it's a good thing to be aware of on a boat, tells you everything you need to know - if you can't fully charge the battery with 6 amps - that battery is bad.


The minimum automotive alternator you'll see is potentially capable of producing at least 50 amps (most are 100+ amps) in the 13.8 - 14.5 volt range, so you can't detect if the battery is charged or charging based on the voltage rise.

So a bad battery often "eats" too much amperage, the alternator carries the operating load and kills itself sending all that excess amperage to the battery (this can go on for weeks with a deteriorating battery).


Often the first observed symptom is a dead battery - followed by less than 12 volts observed at the battery once you get it jumped off + running again.


Hope someone finds some of that information helpful.

[mike223]

On boats, I've typically run outboard motors that only have a 6 amp alternator - you can literally see the voltage rise once the battery is fully recharged if you're watching for it - it's a good thing to be aware of on a boat, tells you everything you need to know - if you can't fully charge the battery with 6 amps - that battery is bad.

A little more detail on this, as I know many smart people who struggle to understand electrical issues.


You get the outboard motor started - you have slightly discharged the battery with the starter motor.

You run down the lake for 5-10 minutes and are seeing ~ 12 volts on the volt meter - because the battery is taking amperage (charging) and you only have 6 amps available.

After 5-10 minutes running down the lake, voltage pops up to ~14.

The battery is fully charged, and no longer taking amperage - no longer dragging down the voltage.

If it never pops up to 14 volts, something isn't right.



But you'll never see that voltage change in a car with a 100+ amp alternator - because it's going to hold ~14 volts - even if it's destroying itself doing it.

[lewma]

Replaced both the alternator and the battery but still getting no charging and ECU is throwing P0620 codes ( Generator Control Circuit Malfunction ). Perhaps the next thing to do is check the wiring harness. Can't see any fuses anywhere so I'm thinking wiring short somewhere. Strange that this all happened after the battery was drained low though.

[mike223]

Perhaps the next thing to do is check the wiring harness. Can't see any fuses anywhere so I'm thinking wiring short somewhere. Strange that this all happened after the battery was drained low though.


Are there any hidden fusible links in the harness wire coming out of the alt? Any in the fuse/relay box?

This is common - check the biggest wire for continuity / hidden (shrinkwrap) fusible link.


Theory = the battery went bad + blew the fusible link in the harness.

[lewma]

Going to start at the ECU and unwrap the wiring in the engine bay. Really don't want to get under the dash.

[lewma]

@mike223. not sure the coyote wiring harness has any fusible links. At least none that I've seen to this point.

[Alan_C]

No fusible link in the controls pack harness, just the main 250A megafuse. There is not much interconnection between the controls pack harness and the RF harness used in most FFR builds. How about a lose signal or ground connection? The problem appeared get worse with time like a connection was failing.

[lewma]

@Alan_C Yep, that's where I'm going to start looking. Hoping to find a loose ground, or something else along those lines.

Just saw you're in Prescott AZ. My son is finishing up his final year at Embry Riddle. That's a cool town!

[Hoooper]

Check ohms for alternator body to battery ground, and also from alternator + to battery + and work backwards from there.

[D Stand]

If you bought a remanufactured alternator I have gone through up to 4 before getting a good one.

[lewma]

Does anyone know if there are specific fuses tied to the alternator and charging circuit in the coyote controls pack ? I started pulling the wiring harness last night and its still all tightly wrapped and I can't believe that a wiring issue is ONLY affecting the charging circuit. I'm wondering if my 'brown out' when I left the ignition on fried something in the ECU and needs to be repaired by ford

[GTBradley]

Does anyone know if there are specific fuses tied to the alternator and charging circuit in the coyote controls pack ? I started pulling the wiring harness last night and its still all tightly wrapped and I can't believe that a wiring issue is ONLY affecting the charging circuit. I'm wondering if my 'brown out' when I left the ignition on fried something in the ECU and needs to be repaired by ford
That was my thought. I mean if the battery, alternator, fusses and connections are all good, what else is there? I’d check with a Ford repair shop to see if they can bench test the ECU.

[lewma]

Just posting for reference so I don't loose this. http://iihs.net/fsm/?d=711&f=012%20-%20Charging%20System.pdf

It says 2011 onwards, and perhaps not entirely accurate considering im using the controls pack. I never checked the Mega Fuse. Assuming nothing would work if that was blown but I'll check it tonight. Ford Performance chat line insists on disconnecting the 3 prong plug then running the engine. I did that last night and got NO charge, measured at the battery. I'll measure tonight straight at the alternator output.

[edwardb]

Does anyone know if there are specific fuses tied to the alternator and charging circuit in the coyote controls pack ? I started pulling the wiring harness last night and its still all tightly wrapped and I can't believe that a wiring issue is ONLY affecting the charging circuit. I'm wondering if my 'brown out' when I left the ignition on fried something in the ECU and needs to be repaired by ford

Nothing listed in the PDB related to the charging circuit. Which would only be for the harness alternator 3-wire plug since the Coyote harness doesn't include the main charging wire between the large terminal and the battery. Some, including me, add a mega fuse there. DD's typically have a fusible link in that connection. But in this case would only have something if you put it there. That cable that you installed should be checked, including the attachment to the alternator, wherever you have it attached on the other end, the crimps and/or solder on the lugs, etc. Without the engine running I would expect to see +12V on the alternator post meaning the battery is connected. The 250 amp mega fuse that Ford supplies is on the main power input. So if that were blown nothing would be working or running. The ground for the alternator is through the attachment to the block and then through your ground strap(s) or cables. Something to check there.

Just looking at the Ford Performance control pack document, it shows pin 3 on the alternator harness plug is "Battery Sense B+ Always HOT." Might be interesting to stick a VOM on that pin and see if it has battery voltage. Again, total mystery why the help line would suggest leaving that connection unplugged. As I said in my PM, and will say here for everyone's sake, I've plugged that in on both of my Coyote builds and have never had any issues. Every other Coyote installation that I know about or have helped with also used it. So bottom line the system works fine with it plugged in. And I suspect it should be. Really question that advice.

[lewma]

Paul, I also questioned the ford tech advice. The root event here is me leaving my ignition on overnight. "Something" changed from that point on. Ford also told me to try another new alternator. The one I have on there now was just pulled out of the box Tuesday night, brand new. I find it hard to believe that I'd have 2 bad alternators. I checked the 3 pin connector last night. Battery Sense B+ is showing battery voltage 12.6V. When I turn on the ignition, the center pin also shows battery voltage 12.6V. That just leaves the 3rd pin to test but I'm unsure how to do that.

I'll check the alternator post tonight when I get home.

Are these alternators "smart" alternators that use the 3 pin connector to be told by the ECU to charge ?

[Norm B]

To quote Edwardb "That cable that you installed should be checked, including the attachment to the alternator, wherever you have it attached on the other end, the crimps and/or solder on the lugs, etc. Without the engine running I would expect to see +12V on the alternator post meaning the battery is connected."

Wiggle the cable ends while watching the voltage at the alternator.

I had the heavy cable for my one wire alternator made up at a local auto shop. Didn't trust myself to do the heavy crimps required for the lugs. Alternator stopped charging after two years on the road. Took the alternator out, had it tested and it was fine. Tested the heavy wire and it failed. Took the heavy heat shrink off the alternator end of the cable and found the cable had slipped out of the lug. Didn't look like it had ever been crimped or soldiered. Soldiered it myself and it has been fine for the last 4 years.

HTH

Norm

[lewma]

I think I may have found the problem. My 4 post battery cutoff switch may be fried. Definitely not seeing any battery voltage at the alternator. I'm still digging but it's best lead I've found all week.

My setup is similar to this: https://thefactoryfiveforum.com/showthread.php?20985-Battery-Disconnect-Switch-with-EFI&p=237789&viewfull=1#post237789

[lewma]

My alternator is on it's own post and that post seems dead on the switch

[edwardb]

...Are these alternators "smart" alternators that use the 3 pin connector to be told by the ECU to charge?

The Ford Performance recommended alternator is a 6G unit. Found this document that describes what the three pins are in the 3 pin connector and how they function along with the PCM. http://www.pantherbb.com/p71interceptor/alternator/convert4g6g/pcmalternatorpdfs/pcmalternator8.pdf. So I think the answer is yes. Although mainly it seems varying the amount of the charge. Which once again begs the question of why tech support would have you disable that function by not plugging in the connector.

But based on your other response, looks like you're onto something.

[lewma]

Solved

The issue was down to me wiring my alternator to a 20amp post in my battery cutoff switch. When I left my ignition on, it drained the battery. I charged it up just enough to get the engine started then drove the car. The alternator was likely pushing way more than 20amps at the battery while it was being driven and recharging. The cutoff switch gave up.

I'm now using a 4awg wire from my alternator and have it wired up to the larger posts in the switch ( I plan on replacing the cutoff switch too ).

Cranked it up and now I'm seeing 14.9V and no more P0620 codes either.

Bad wiring design on my part in the beginning. Lesson learned.

mark.

[edwardb]

Great news. Glad you got it sorted out. That was going to fail at some point with or without a drained battery. In hindsight, not complicated. The unchangeable rules of electricity strike again. ;)