Theorists apply

[jake7140]

1968 1600. Taillight wiring seems to concur.
Why might a PO cut the big white alternator wire, splice in a wire which then runs directly to the battery?
- likes explosions?
- bad external regulator?
- bad ammeter?
- generally doesn't have a clue?

Though it of course worked, I drove last summer with the lights and fan on high. Still a little over cooked. The guy I bought it from (who had never run it) was all excited to tell me about the half dozen underdash regulators that were apparently of varying accuracy.

So before I dove under the dash, quite the task for a fat old nearly blind man soon to undergo carpal tunnel and ulna surgery so I get some feeling and strength back,where should I start.?

- follow that white wire and see if any other nefarious electrical work has been incurred?
- remove ammeter and test (continuity?)

It's been since winter since I scope out the wiring diagram, but it will be resurrected. Thanks in advance!

[JT68]

So...my guess is the PO was having intermittent charging issues and tried this as a bypass. The big white wire DOES actually route to the battery+. First it goes through the dash harness to the ammeter, through the ammeter, back out the dash harness to the +battery cable at the starter...So a direct line to the battery from the Alt won't really do much harm, it just bypasses the ammeter and all the under-dash connections.

In fact, most GM's are wired that way with a fusible link since they don't have ammeters. The additional wire is completely unnecessary of course if the harness is in good shape, it just provides a parallel, redundant path //j

[redroadster]

The white charge. 1 wire type, wire goes to the positive terminal after the 100 amp
Link , it only charges thru the pos side. But if thru a ext v reg likely it will not charge. He may have wired a ic reg in.
I had a volvo 123gt 68
Very cold the reg did not perform well i set it to ful charge. It did blow a bulb or 2 but got me around until it warmed

[jake7140]

So I re-read the service manual section on dynamo and regulator. Very interesting wording in THAT section.
But I now fully understand that the alternator output is regulated, not that the alt is always putting out full power, which is then regulated. Big diff.

So, theoriginal issue of the battery being charged at around 17v would seem to indicate that the external regulator is not functioning properly and not correctly regulating the output of the alternator?

So I'm thinking to swap in another regulator (the current one does humm/buzz when there is no draw, and quiets when I turn on lights), make sure all grounds are clean and try it with the spliced wire still direct to battery. If that is then seeing good regulated voltage, then look at checking the ammeter and reconnecting the white wire into the harness. Sound reasonable? Don't want fry a harness.

[Curtis]

Mine is wired straight to the battery. IR Nissan/Datsun alternator. Works just fine. My ammeter has been converted to a voltmeter.

Your car must of have had some issue. I would check the condition of the harnesses and look for any melted tape or wire.

[C.Costine]

My '67 had the white bypassed with TWO fusible links in line. The lights were also bypassed due to a burned out connection in the connector where the dash and engine bay harnesses connect.

[redroadster]

Some who like thatTHUMPITY'THUMP...THUMP
Loose rear plate rattling noise( like our new neighbor) will splice in the power to the sub woofers of the alt output as not to pull down the battery. As much

[jake7140]

Put in presumably good voltage reg and things went well. Then went on to getting the wiring sorted. Found the cut white wire in the harness and after checking out under the dash, etc, reconnected to alt, ditched the direct to battery wire. Now have power to multi-gauge. Ammeter seems to read high, fuel waaaay to E and I know I have almost full tank. Perhaps dash voltage reg? I have a bunch extra, or maybe go solid state.

Found the cut temp sender wire in the engine bay, jumped it to the sender in the head, but temp gauge non-op.

Can I remove the multi-gauge directly without dropping the dash to check wiring?

[JT68]

Yes, the multi (cluster) gauge can be removed with the dash in place, requires small fingers, its pretty tight and challenging as I recall. But i wouldn't do that until you rule out everything else. Since you're having problems with both the temperature gauge and the fuel gauge, that little regulator is highly suspect or the wiring to it.

Try shorting the two wires for the fuel tank sending unit together. That should peg the fuel gauge.
Shorting the yellow temp wire to ground should peg the temp gauge.

All the gauges in the cluster unit are fully independent, so the odds of several of them failing at once is fairly small.

I'd work on that regulator circuit first and make sure the multi pin connector at the back of the gauge is plugged in.

Also make sure that little dash regulator isn't hooked up backwards, it won't work if so. And oh yes, that little reg must be well grounded well (screwed to chassis) to work properly

[Curtis]

Here's a photo of the back of the ammeter/fuel gauge. You can see the terminal markings and that it is held on with 3 screws or nuts. Not easy to get off.

IMG_2377.JPG

[jake7140]

Ewww, definitely looks like a pain to get out. Thanks Curtis. I knew there was more than looks why I like flat dash cars!

JT; is the regulator marked +/- or something? The wiring diagram doesn't indicate any markings, just the two wires going to it. Wouldn't hurt to switch around and watch I suppose? Good tip on the other two grounding. Who knows if the fuel sender is even hooked up. There was a lot of 'just hanging around' wiring when I got it.

Are you saying the non-ammeter wires come together in a pigtail to a plug that's maybe 4-5 inches long? If so I could use that to check/follow wires.

On the way to surgery in 5 mins, so will be dark for a while. Thanks, it'll give me something to think about as I drift off. You know lots of problems get solved ina dream state!

[Curtis]

Here's the 68-70 combo gauge. Two screws or nuts to hold it on.

IMG_2378.JPG

[jake7140]

SUPER! Thanks

[jhayden]

JT; is the regulator marked +/- or something? The wiring diagram doesn't indicate any markings, just the two wires going to it. Wouldn't hurt to switch around and watch I suppose? Good tip on the other two grounding. Who knows if the fuel sender is even hooked up. There was a lot of 'just hanging around' wiring when I got it.

Steve,

Been quite a while since having to deal with this issue personally, but tip nr. 1 seems to address your polarity question:

https://risingsunracing.com/index.php/f ... -tech-tips

Hope everything goes well with your surgery.

Jon

[jake7140]

A little more searching on 311s, found a pic of the dash vr, and it was backwards. Hooked b/w wire to ign pin, yellow to plain and got some life from fuel and temp! The are both slowly going up and down, so will clean grounds, test and try some other vr perhaps and move on. But things now seem to at least be in the right place and ready to function!

Thanks to all for your insightful help and ideas.