Battery Charging Issues

[ReMorton]

Am experiencing battery charging issues. Ammeter shows constant slow drain, does not go positive regardless of rpm. Replaced voltage regulator; sent alternator to rebuld shop, verified as working. Electrical connections seem fine. Running out of things to check. Short somewhere?
Any suggestions or further troubleshooting ideas?

[Riverside racer]

Faulty gauge? Disconnect at back of gauge and use a multimeter.
Ross

[Blue Cobra]

ReMorton,

Plastic cars, boats and motorhomes can be a bugger when it comes to grounding circuits, and especially over time thanks to the physics of electrical flows, the process of electrolysis can oxidize and/or create corrosion on, around, under the connectors and posts, and within the strands wires themselves, creating increased resistance or eventually a lack of ground entirely.

So if it was me, I would start at the battery (-) post and follow the ground path to where the alternator is grounded, likely the engine block, and inspect each connection and cable for oxidation. remove connectors sandpaper or wire brush the parts to remove any chance of oxidation or corrosion causing resistance or breaking the circuit. As I connect them together, I always try to use a AntiOxidant when ever possible on connections (especially aluminium connectors), even if it's just wheel bearing grease, even better fancy stuff like this:
1oz. Antioxidant by G B Electrical Inc - OX-100B - More Wiring connectors and terminals at doitbest.com

Then next follow the path from the output (+) of the alternator back through all the crap to the battery (+) post. This will assure that all connections are not oxidized to the point of creating enough resistance to not recharge the battery even though the alternator is working.

Are you using a traditional Ford wheel-well mounted regulator? Or using a one-wire regulator like the Transpo F7078 which mounts to the rear of the alternator? I use the F7078 and have not ever had a problem in 13 years, although I rebuilt my Motorcraft alternator this summer due to blown diodes. If your using the one-wire regulator double check how it's wired in. If you are using the traditional Ford regulator, do the same wire path investigation I recommended above but include the regulator too.

Finally how old is your battery and is it in good shape? Unless you consistently use a battery float charger during the months that a Western Washington Cobra sits in the garage, from personal experience I find that the battery ages quickly, much quicker than normal. Boats and motorhomes are the same way. My Corvette is horrible without a float charger the battery goes dead in a couple months of sitting. Older batteries in cars that sit for long periods un-driven and not on a float charger, can appear to be fully charged showing 13+ DC Volts at rest, but when it's time to put out the AMPs needed to spin a cold high-compression big block they choke and puke.

Sounds like the alternator has been tested for output on a bench, dumb question but have you done a stress test on your battery to see how many AMPs it will produce and how long it will hold the AMPs it does produce? This could be another issue creating a 'charging' issue where the alternator and regulator are fine and the battery just does not take the deep charge anymore, or the battery is fooling the regulator with the correct voltage range making it think is is fully charged, yet no cranking power when the key is turned.

Nice rainy weekend ahead for working in the garage on the Cobra, that's my plans.

Cheers!
BC Kevin

[ReMorton]

Thanks for the replies, and Mike for the phone call. It seems to be the consensus, that this winter the project will be the grunt work of tracing down all the wires for shorts and or oxidation. I love tinkering with the car, cant drive it in th ewinter anyway, so an excuse to hang out with the beast when I'm home on the weekends.
The battery checks out fine, when the engine is off 12.8 volts, even if it's 8 yrs old, dash gage is working and the VR was replaced, its the one with multiple connections. I did not check the voltage when the engine was running however. Big oops, as a higher voltage would indicate charging, then I might be able to isolate the problem to a short across the 8 yr old battery.
I had a similar situation with a 71 MGB, (Lucas, of course) where I had a slow drain and the starter wouldnt work consistently. I initially looked at the electrical cable to the starter and it looked OK. Several days later after no progress I yanked on the cable and it broke midway. I replaced the cable and problem solved.
I seem to recall that you lost your top end this summer after the run to Oregon and were not able to make it up here for Tim's run to Mt Baker. We had a great time and they werent (too) embarassed to having a black 91 vette bringin up the rear of the pack.. (I could run with them on the corners, but hopeless on the straights.) Hope the engine work came out and you're back up and running this spring.
Bob

[HighPlainsDrifter]

Hi,
Do you have an msd ignition box?
If so then the large capacitor in it is probably leaking / shorted / lower resistance than it should have.
I would suspect it as that is connected to the battery at all times.
Good Luck,
Perry.
ps- ammeter gauges that short out can cause a red hot wire and burn down the car, I would leave it disconnected or replaced with a voltage gauge.

[ReMorton]

Hi Perry- Yes, will put it on the check list, thanks for the tip, exactly the type of comments I need. Thanks, Bob

[Gaz64]

What is your charging voltage at the battery?

[ReMorton]

Battery shows 12.2 volts with key off, 12.2 volts with engine at 2500 rpm. Second VR installed, no difference. Checking MSD box this weekend

[Blue Cobra]

Sure sounds like a bad alternator. Depending on where your alternator is mounted you may be able to put 12VDC directly from the battery in to the alternator windings and manually force your alternator to crank full amperage. Pretty much a bench test on the car. Coupled with watching your Volt meter you should see those 12.2 numbers jump up to the mid-13 to 14 VDC range. A healthy battery at rest fully charged should volt meter about 13+ volts.

[ReMorton]

Priblem fixed after spending much time doing continuity checks.
Diode to VR was blown (see No 5 fuse box, slot 9 in Superformance OM). Electric choke wired to wrong side of alternator. Root cause is believed to be to the incorrect wiring of the electric choke, cascading ultimately to diode blowing out. May have also been root cause of constant 15 amp fuse issues with turnsignals/fan.
Also found some wire colors didnt match wiring diagram.
Diode replaced, choke wiring redone correctly. Ammeter now more stable when switching electrical components off and on.

Since no one has monkeyed with the electrical system, I asume this is another quality issue left over from the orignal Park Place Motors install.

Thanks all for the useful tips. Still bummed that I didnt make the Mt Baker run, although really dodged the bullet in this case, failure could have taken place on the road instead of driveway..

Work was done by 'Mike' at MC Automotive in Lynden WA. 360 318 4163. Highly recommend for us guys up here in the north side for wrenching you dont have the time do. Didnt charge an arm or a leg either.

MPS dyno now in another shop Nooksak. Will provide info if anyone is interested.

[Blue Cobra]

Good news indeed.