Voltage Regulator and Alternator

[MidLife1977]

Greetings. New to the forum. Strange electrical issue so will try to summarize it in bullet points and get your insight. This is a 1977 FJ40 with 2F engine, external VR on firewall.

• Noticed headlights and dashlights seemed brighter, also flickering simultaneously.

• So Replaced VR - resulted in no charge coming back from alt. to battery (dash gauge around -20amp with lights on and running)

• Replaced alternator - no change in reading or charging level

• Replaced with second VR (factory plug on this one) now dash gauge points well to the +side. Took a reading of 16.5 volts at the battery

• Thinking I may have plugged the VR connections incorrectly on the alternator, I switched one wire to the vacant blade on the alternator, voltage reading at the battery went up to 18v

• Switched same wire back to original blade on the alternator - now no voltage at all. Back to original condition.

Any guidance on what's going on? This is driving me and my checking account crazy.

 

[Solace in Solitude]

Here’s Rudi’s (@bj40green) great explanation of just how external voltage regulators work. It also provides some insight into wiring connections between the VR and the alternator.

Voltage Regulator (ext.) / How it works

 

[GA Architect]

Greetings. New to the forum. Strange electrical issue so will try to summarize it in bullet points and get your insight. This is a 1977 FJ40 with 2F engine, external VR on firewall.

• Noticed headlights and dashlights seemed brighter, also flickering simultaneously.

• So Replaced VR - resulted in no charge coming back from alt. to battery (dash gauge around -20amp with lights on and running)

• Replaced alternator - no change in reading or charging level

• Replaced with second VR (factory plug on this one) now dash gauge points well to the +side. Took a reading of 16.5 volts at the battery

• Thinking I may have plugged the VR connections incorrectly on the alternator, I switched one wire to the vacant blade on the alternator, voltage reading at the battery went up to 18v

• Switched same wire back to original blade on the alternator - now no voltage at all. Back to original condition.

Any guidance on what's going on? This is driving me and my checking account crazy.

In case you need the '77 wiring diagram, here it is.

Note, it is a good idea to at least buy a silver star to post up some photos.

 

[GA Architect]

Greetings. New to the forum. Strange electrical issue so will try to summarize it in bullet points and get your insight. This is a 1977 FJ40 with 2F engine, external VR on firewall.

• Noticed headlights and dashlights seemed brighter, also flickering simultaneously.

• So Replaced VR - resulted in no charge coming back from alt. to battery (dash gauge around -20amp with lights on and running)

• Replaced alternator - no change in reading or charging level

• Replaced with second VR (factory plug on this one) now dash gauge points well to the +side. Took a reading of 16.5 volts at the battery

• Thinking I may have plugged the VR connections incorrectly on the alternator, I switched one wire to the vacant blade on the alternator, voltage reading at the battery went up to 18v

• Switched same wire back to original blade on the alternator - now no voltage at all. Back to original condition.

Any guidance on what's going on? This is driving me and my checking account crazy.

Connections at the Alternator:
White wire with blue strip (WL) is connected to the "B" post.
White wire with black strip (WB) is connected to the "E" male termial
White wire with green strip (WG) is connected to the "F" male termial

 

[MidLife1977]

So just for kicks, I took off the regulator, checked the ohms per the FSM, and the readings didn't get up to 100-ohms, just up to 66. No burns or fusing visible, seemed in perfect working order. I put back on the old alternator, reconnected the VR, and now it's running high voltage again. The Ammeter on the dash reads about 15+ with lights off, and about 0 with lights on. Photo shows how it came from PO and how it is configured right now. I'm sure I'm missing the plug like shown above. Do you think the VR is worth adjusting?

 

[Solace in Solitude]

It's a cheap test... and not difficult.

 

[MidLife1977]

Third VR is the charm! Tested this one against the FSM specs before putting it in. Voltage still ran high, but unlike the second one, it operated correctly after making the adjustment. That said, I have an extra alternator and another VR in the mail. I guess I'll put them in a box for sometime in the future! Thanks for the input!

 

[MidLife1977]

As I've read with many other owners, the flickering lights continue, albeit not all the time. I took these two photos and would like some feedback. The first is of the white wire feeding from the harness to the fusible link. Note the break in the insulation, but the wire appears intact. Second is the ground from the alternator to the chassis. I've cleaned the connection but wonder if the ground wire itself could be bad based on the photo. Any chance either of these could cause the flickering and mixed signals to the voltage regulator?