Charging System Troubleshooting--Blown Ignition Light Fuse?

[patrickt]

Originally Posted by ACHiPo

I don't understand why the fuse would blow since the "I" was disconnected, basically taking the ignition light out of the circuit?

I would guess that the short to ground is upstream on the Green line. Perhaps at the tach, or the wipers, or the wiper switch. Leave Fuse 3 out of the car entirely, check and replace any other fuses that may have blown, and start the car up again with the modification that you made to the VR at Bob's direction. Run the engine and check your system voltage with headlights on, etc., and see if you have a nice 13 or 14 volts, which would indicate that the system is charging normally.

[ACHiPo]

Originally Posted by patrickt

I would guess that the short to ground is upstream on the Green line. Perhaps at the tach, or the wipers, or the wiper switch. Leave Fuse 3 out of the car entirely, check and replace any other fuses that may have blown, and start the car up again with the modification that you made to the VR at Bob's direction. Run the engine and check your system voltage with headlights on, etc., and see if you have a nice 13 or 14 volts, which would indicate that the system is charging normally.

The only fuse that blows is Fuse 3. I'm going to disconnect the tach. I don't know if I can get to the wiper switch or heater. I will check charging voltage assuming I can get things to run in Bob's configuration.

The system charged normally for about 60 seconds with Bob’s configuration. It doesn’t seem that charging happens with fuse 3 blown.

[patrickt]

Originally Posted by ACHiPo

The only fuse that blows is Fuse 3. I'm going to disconnect the tach. I don't know if I can get to the wiper switch or heater. I will check charging voltage assuming I can get things to run in Bob's configuration.

The system charged normally for about 60 seconds with Bob’s configuration. It doesn’t seem that charging happens with fuse 3 blown.

With Bob's new configuration, you do not need a fuse in holder #3. You only need that fuse to charge with the previous "indicator light" configuration. The fact that the circuit on fuse #3 was in the process of faulting out can give you confusing results, so you should dismiss that until you've tested further.

Remember that Green wire also runs to the wiper motor over on the passenger side foot box. That plug is really easy to pull, so go ahead and pull it when you're ready to trace for the fault on the two branches of Fuse #3. But I would first test Bob's new configuration, all the while leaving Fuse #3 completely out. The only way Bob's configuration won't work is if there is a bad VR, a bad alternator, or a bad connection between the two. I think it will charge fine. In fact, I think I'm in a position as to guess what happened to cause all this mess, but I'm going to hold that card close to the vest for now just in case I'm wrong.

[ACHiPo]

Originally Posted by patrickt

With Bob's new configuration, you do not need a fuse in holder #3. You only need that fuse to charge with the previous "indicator light" configuration. The fact that the circuit on fuse #3 was in the process of faulting out can give you confusing results, so you should dismiss that until you've tested further.

Remember that Green wire also runs to the wiper motor over on the passenger side foot box. That plug is really easy to pull, so go ahead and pull it when you're ready to trace for the fault on the two branches of Fuse #3. But I would first test Bob's new configuration, all the while leaving Fuse #3 completely out. The only way Bob's configuration won't work is if there is a bad VR, a bad alternator, or a bad connection between the two. I think it will charge fine. In fact, I think I'm in a position as to guess what happened to cause all this mess, but I'm going to hold that card close to the vest for now just in case I'm wrong.

Patrick,
If fuse 3 is not required in Bob's configuration to charge, why did the car charge when there was a fresh fuse in # stop charging yesterday and the fuse was blown?

I did receive my short tester, but I'm not quite ready to go down to that level of detail.

Just got off the phone with Doug. One thing not shown on the schematic is a voltage shunt on the fuel gauge. I think, Patrick, this is a similar circuit to what you retrofitted? He suspects that may be the issue, and also since it's installed, the test I did to isolate the fuel gauge did not in fact remove the rest of the circuit. Just wish it was a little easier to reach up in there and access that stuff!

[patrickt]

Well, I can't be really sure until you retest with fuse #3 out. If everything is wired exactly as the schematics for a non-indicator light have all shown for the last 75 years, then the only positive feed that goes to the voltage regulator is coming from fuse #4. That feed from fuse #3 was only to show the indicator light and excite the VR. If you are not using the indicator light then the change in the feeds to the VR gets everything going. BUT, now that I hear that there might be wiring under there, that is on the green line, of which I am totally unaware, well that puts a new spin on the game. Did Doug tell you where he mounted that "shunt," which sounds like it is a 10v Smiths regulator just like what you see in my pic. Yes, that would be a prime candidate for failure.

[ACHiPo]

Originally Posted by patrickt

Well, I can't be really sure until you retest with fuse #3 out. If everything is wired exactly as the schematics for a non-indicator light have all shown for the last 75 years, then the only positive feed that goes to the voltage regulator is coming from fuse #4. That feed from fuse #3 was only to show the indicator light and excite the VR. If you are not using the indicator light then the change in the feeds to the VR gets everything going. BUT, now that I hear that there might be wiring under there, that is on the green line, of which I am totally unaware, well that puts a new spin on the game. Did Doug tell you where he mounted that "shunt," which sounds like it is a 10v Smiths regulator just like what you see in my pic. Yes, that would be a prime candidate for failure.

Doug told me it's a 3/4" x 1 1/2" silver box that he tucked up between the gauges. It came with my fuel gauge from Nissonger. Since Doug wasn't familiar with the gauge, he just installed the shunt since it came in the box with the gauge. I assume it's a Smiths stabilizer.

I just pulled the steering wheel, removed the foot box fan switches, and dropped the dash to better see under there. I sure don't see it. I need to get ready to go out, but will be back at it later this afternoon.

Here's a photo of the Smiths stabilizer I pulled from Google. It's not what I was looking for, so I will look again this afternoon. Man it's a jungle of wires and connectors up there!
https://i.ebayimg.com/images/g/Gi8AA...gI1/s-l300.jpg

[patrickt]

Yes, be on the lookout for something like this. As I recall, mine said it had to be mounted to a grounded location, so look for a mounting on the aluminum. I mounted mine over by the MSD unit above the passenger's feet. Doug's a pro, and does stuff in a very logical, predictable manner. Take some pics, I'm curious as to where he might have tucked it in.