i will pull the battery and have it checked

Cucu:
I pulled the battery and took it to a local parts store. The boys had a $1500 electronic tester.... Anyway the battery checked out excellent.
I thoroughly cleaned up the terminals and battery cables and reinstalled the battery and rechecked the VR blue wire voltage. There is still a 1 volt drop from the battery to the VR.
Where do I go from here?
Glenn

you need to find where the drop is coming from. it has to be some where there is a connction. eith the starter relay on the fender, the fusable link may be bad (resistive but not open), the bulkhead connectors, eyc. just get a schematic and trace the wire from the VR back to the battery.

a way to check to make sure Im not sending you on a wild goose chase is to rig up a jumper to the Blue wire. start the car and watch it over charge, then connect it staright to the battery post (so you eliminate ALL the connections). if the charging goes down to normal, you know the cars wiring has a bad connection somewhere. the trick is finding it.

Update:
Cucu, I stripped off a little insulation off the blue wire a couple inches below the VR plug and spliced a jumper wire to the stripped blue wire. The jumper wire was a heavy stranded wire to minimize voltage drop. Anyway the voltage is 15.1 volts through the normal bulkhead circuit and 14.9 volts through the jumper.
I was expecting a bigger drop... Should the voltage be between 13 and 14?
I pulled each field wire off the Alt, one at a time and voltage dropped from 15.1 to 12.9.
What do you think? Could it be a problem in the new harness?

yes, the voltage should be 13-14v. but right now your battery is at 12something so it may be trying to charge the battery.

when I go home tonight. I'll put a meter on mine and tell you what Im getting. In the meanwhile. put a battery charger on your battery and charge it up for a while making sure you dont dump too many amp into it (limit the charger to 10 amps max)

you may have just a weak battery causing the alt to push out some volts or the Voltage regulator may be bad.

in the meanwhile take out a bolt on the VR and make a ground strap to make sure you have a good ground.

ok, im home and i made some measurements. car hasnt been started in a week.

With the engine off, Ign off i get (all measurements made with the voltmeter neg lead on the batt neg post)

V @ batt = 12.5v
V @ alt out = 12.5v (notice it is the same as the voltage at the battery. it should be)
V @ Alt Blue field = 0v (it should be 0v cause ign is off)

With the Ign ON but the car not running, I get

V @ Batt = 12.4v
V @ alt = 11.92V (The load from the ign plus the resistance of wiring is pulling down the batt voltage slightly. thats normal)
V @ Alt Blue Field = 11.2 v (no comment)

With the Ign ON, and Car running at 600 rpm

V @ batt = 14.11 v (alt is charging the batt)
V @ alt out = 14.3 V (alt voltage is slightly higher than Batt cause of wiring reistance between alt and batt. its normal)
V @ Alt Blue Field = 13.8V (since the alt field (ie, the ign voltage, is 13.8v, , the VR will charge slightly but not too much. just enough to maintain the battery and run the car stuff)

With the car at 1400 rpm, the V @ alt Bleue Field is 14.0 (its still maintaining. not overcharging).

Turn car off

V @ batt = 13.2 V immediately and decays down to 12.7v after a beer or two.


v @

Hi, guys, I've had some 'puter problems and haven't been following this. Cuco has given you some EXCELLENT advice. It almost sounds to me like that as you've been moving/ wiggling stuff, etc, you may have "made" a bad connection better.

I CANNOT STRESS ENOUGH both cucu and myself, the advice we've given re: checking voltage drops, that is voltage loss UNDER LOAD through various wires/ connections, etc.

The firewall/ bulkhead connections on these cars have become just about the no1 suspect.

and one last time YOU CAN NOT check a regulator ground with an ohmeter. That is because current causes voltage drop over resistance called "ohms law" Let's say you have ONE TEN TH just ONE TENTH of an ohm resistance between the battery negative (post) and the regulator case. With some 60 amps (or more) ohms law says thus:

I (current in amps) = E (voltage) / R (resistance)

Transposing, E = I x R

so Voltage = 60 amps X .1 ohms

You now have SIX VOLTS DROP over that one tenth of an ohm

The point? You can measure the voltage drop under load, but YOU CAN NOT measure one tenth of an ohm with common meters.

Additionally, many drop problems are through corroded/ intermittent connections, which do not show up until heated up and loaded under current.

One more last point. YOU CAN NOT check high-amperage diodes in alternators with an ohmeter, even ones with a "diode check" feature.

YOU MUST check high current rectifiers by running considerable current--10-30 amps through them, and once, again, checking the voltage drop!!!!

absolutely!! voltage drops are the way to diagnose electrical systems. Ohms will tell you if you have continuity...well thats wonderful, but it won't tell you if it can take any amount of current!

Thanks '440sixpack, cucu et al. Your help is much appreciated.
I plan on bypassing the bulkhead connector on the high current wires and will make sure the Voltage regulator is grounded. Is there a test to check a VR for proper function.
Funny thing is I worked as an electrican for a couple years and spent two years in school studying electrical construction. That was 1981 when I was 21. I am used to a white neutral wire to complete circuits.
Glenn