88 240 not charging, checked all i can think of

cbarth · Post by **cbarth** » 29 Jul 2014, 09:20

I've read through all the posts I can find but am still stumped.
240 (244); new battery (good), 3rd alternator (good, this one tested before I purchased)
voltage on B+ post matches battery voltage, usually 12.2-12.6
Same voltage on D+ (not running, key on)
Perfect continuity between B+ and battery positive
Perfect continuity between alternator casing and battery ground post
Key on, not running, battery light on dash is on, goes off when running
I've run a direct ground from the alternator case to the ground post of battery
I've run a direct hot from B+ to battery positive

So, to summarize, 12v coming through exciter wire, good ground, good continuity from B+ to battery hot post. What's left?????

93Regina · Post by **93Regina** » 29 Jul 2014, 11:58

cbarth wrote: I've run a direct ground from the alternator case to the ground post of battery
I've run a direct hot from B+ to battery positive
What's left?????

Leave those hooked up, and run another wire from exciter to + battery.

I'll assume 12 gauge wire is being used for all three wires..

Post by **jimmy57** » 30 Jul 2014, 22:46

With engine running check with voltmeter between case and block, should be 0.2V or less and between + lug and battery + terminal and should be less than 0.3V.

Continuity with ohmmeter will get you in trouble on high current carrying wiring. 2 strands of wire connected out of 64 strands in the wire will give you continuity but have HIGH voltage drop.

cbarth · Post by **cbarth** » 31 Jul 2014, 07:14

thanks to both. finally at the point where my work schedule allows me to do some additional testing. will try these today and report findings. Sounds like I could have a bad cable somewhere along the lines...

cbarth · Post by **cbarth** » 31 Jul 2014, 10:45

OK. I removed all 3 wires from the alternator. Ran a ground from the case to the battery negative and then 2 direct lines, one from B+ and one from D+ to the battery hot post. No change.
I then reconnected everything and measured voltage while running. Battery 12.3, D+ (exciter) 12.5, B+ 12.7
I know anything is possible but could this have an external regulator somewhere that could be preventing the voltage from exceeding a certain amount? If that were the case, I would think that the voltage would be consistent though, meaning the battery would always read 12.2 or 12.6 or whatever...

93Regina · Post by **93Regina** » 31 Jul 2014, 11:28

cbarth wrote:while running. Battery 12.3, D+ (exciter) 12.5, B+ 12.7...

I hope engine RPM was increased....

1990 ELECTRICAL Alternators & Regulators

cbarth · Post by **cbarth** » 31 Jul 2014, 11:35

yes, rpm was increased

just walked past the car and for some reason thought I'd check voltages while it was sitting. I check across the battery, battery hot to block, battery hot to alternator case, B+ to block... All 4 measured 12.97

93Regina · Post by **93Regina** » 31 Jul 2014, 12:22

cbarth wrote:... All 4 measured 12.97

I realized alternator was "checked," but have them check it again, with your voltmeter.

Otherwise, 1990 ELECTRICAL Alternators & Regulators

cbarth · Post by **cbarth** » 31 Jul 2014, 12:31

its actually the third alternator. I replaced it, same results so returned it. Same results, argued with them to get a third one and had them check it before i left. i stood there with a meter and it was putting out 14.5

cbarth · Post by **cbarth** » 31 Jul 2014, 12:37

There are two items mounted to the firewall next to the battery. no markings. One of them is a rectangular silver "box' about 2 inches wide and an inch and half or so tall. It has I think 5 wires going into it. There is also a thin black box with some red wires going into it, one of them pretty good sized.. any chance one of them (the silver one mainly) could be an external regulator? I'm trying to post pictures but can't seem to get them posted.