My new to me 65 Montclair has a slight battery drain if it sits for some time,checked the usual truck,glove box light and other stuff and nothing staying on so now on to the charging system. What I was wanting to know if that style of alternator could have a diode go bad and cause a drain,regulator was bad when I first got it running and was replaced with a known good used one but could also be the cause so how can one tell if its the alternator or regulator causing the drain.
I've never seen a regulator internal or external cause a drain on it's own. Parasitic drains can be caused by a number of things though. Electric clock under hood light, Trunk light. Probably not on that car but for sure on my OT daily a lighted makeup mirror that stays on if you don't close the cover over the mirror. Wife would check herself in the mirror and flip the visor back up without closing the cover and the light stayed on. The old OT had a cover on it's mirror that flipped up and had to be closed to raise the visor. radio with a clock or other things that take a minute bit of power to operate. The other OT drains in about a week of sitting because of this. The aftermarket radio draws some power even when it is shut off. Dirt and moisture on top of the battery. Take your volt meter and put the positive clamp on the positive post and touch around on the top of the battery with the neg lead. I had a student who's battery was going dead in three hours in the parking lot and we finally figured out that he had a 9+ volt drain across the top of the battery because of the dirt and moisture on it.
put a test light between the battery cable and the battery terminal, if it lights, you have a drain somewhere. Start disconnecting stuff, until the light goes off.
Test light did not come on so must be the battery, I cleaned the top of the battery and is on the charge. The only way I know the battery is loosing charge is the car has a amp gauge and it pegged and when I got home and stuck the charger on it was charging at 4 amps so the battery is going low,if it had a idiot light I would probably not know it was loosing charge until it gets very low and will not start.
You can measure the alternator output under load (lights and accessories) with basic test equipment. A voltage drop test would be a good one to start with, a roasted diode would cause problems. Here's a good link to some checks: https://www.aa1car.com/library/charging_checks.htm
I had a 70 Lincoln with a small solid state regulator that bolted on the rear of the alternator. In the 5 or so years I owned it, the battery would sometimes go dead. I never could find a draw until one time I was working near the alternator and noticed the field was energized (wrench was pulled to it by magnetic field). What was happening was the regulator would sometimes turn on the field with the key off. Replaced the regulator and never had another dead battery.
Ford made both a mechanical and a solid state regulator…the sold state can cause a draw especially if you plugged it in before you grounded it…
Another way to find a draw is with a good digital volt meter. There is a very small voltage drop, milli volts, across a fuse when current if flowing. With everything turned off on the car, you can connect the meter across each fuse. If there is no current flowing the meter will read zero. The first fuse that gives you a reading is in the circuit that is drawing current.
It does have a solid state regulator and now remember a neighbor have a drain on his LTD with the same type regulator that could not be detected.
These regulators are very sensitive and need to installed and grounded…we always ran an extra wire to one of the mounting bolts…then mount the regulator with the new ground wire attached before you ever plug the wires into the regulator. What most people fail to understand is this regulator has a wire that is hot all the time and that creates these issues. For a final check you could simply un-plug the regulator and do a before and after voltage check. A fully charged battery is static voltage 12.6volts….if the regulator is the problem the next morning the battery voltage should be the same with regulator un-plugged.
Since its a used regulator I am going to pick up a new one tomorrow and will have it mounted before it gets plugged in.
Ford installed a dedicated ground wire from the alternator case to the regulator base. That really needs to be there...
Get back to basics. Verify the battery is fully charged, can hold a charge(24hr after charged is a good time-frame to check), and is clean. Spilled electrolyte acts as a conductor and will drain(through shorting) a battery. Verify the main grounds and bonding wires are clean and tight. Verify the regulator is properly bolted with a clean connection(grounded) with a nut/bolt to the car body. Factory screws are junk. I prefer 1/4-28 hardware and some Ox-gard to protect the connection. Clean the sheetmetal and VR feet of paint/corrosion, a dab of ox-gard and then bolt down. Verify the VR to ALT harness is in good condition with good connectors. VR side can be de-pinned using a pick. Replacement female .250" spade connectors can be used, just remove the insulating boot to fit inside the VR connector. I usually find the wire at the connector is what's toasted/rotten, but you can't see it as the plastic VR connector hides it. Verify the VR to ALT harness is correctly wired to the proper IASF connections between components. I > Excite wire goes to dash light bulb. *Factory Amp gauge does not need/use this.* A> Battery(BAT)terminal on Alternator. *If a cap/condensor is used verify it is not grounding out* S> Stator(S) terminal on Alternator. F> Field(F) terminal on Alternator Verify the VR to ALT bonding ground wire is in good condition and bonded/bolted to the V.R. foot. I always add a body ground from the negative terminal to the radiator support/inner fender/firewall(closest to battery) to bond the battery negative to the car body. Using a stud and a simple #10 wire to bolt it, with Ox-gard, to promote a complete circuit. That braided block to firewall connection is often the main ground to body for the battery. Not really something you want to rely on as the sole body ground. It was good 'nuf for a car that was only anticipated to be on the road for 8years ~65 years ago.
Put the meter on the battery tonight and the battery was resting at 13.9 volts which I thought was strange since I took the charger off yesterday,put the meter on the custom 500 and it was resting at 12.7 so its not the meter. Had three old style mechanical regulators hanging in the garage so time to see if they are any good,the first one was putting out 16 volts so off it came and the second one would make the amp gauge flutter at idle but put out the correct voltage but off it came and the third one worked good and the voltage started to drop like normal after running awhile so its going to stay if it does not drain.
If the battery static voltage is higher than 12.6 to 12.8 you probably have a shorted cell and the battery is bad.
A shorted cell is different, it will read lower by exactly one cell, or about 11.5 volts. A battery that has just been run in the car, or recently charged, will measure about 13.10 volts. This is called a surface charge and needs to be removed for testing. The easiest way is (engine off) to turn on the HI beam headlights for 5 minutes, turn them off, and wait for at least 10 minutes. The battery will "bounce back" during that 10 minutes to the true state of charge, or near enough.
A hour or slightly more after running its still showing 13.19,I will turn on the lights for a few minutes.
Keep in mind a battery can read "full" 12.65 volts and still need to be charged, it's a capacity or ampere hour thing. Sealed "maintenance free" batteries will read 12.80 volts at 77° F. when fully charged. It isn't a full load test but simply disabling the ignition and cranking the starter over for about 15 seconds will give a really good indication of battery health. Measure battery voltage across the posts while cranking, a good strong battery will probably hold above 11 volts. 9.6 volts is considered the cutoff = Bad.
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