FJ40 Voltage too high and too low

[NW Oregon 4me]

My 71 FJ 40 has issues with the charging system. the system was checked and alternator voltage at idle was 0. After replacing the Alternator and regulator TWICE, problems continue. An alternator shop bench tested the alternator and it’s OK. The regulator is the commonly found cheap import with no labeling. Big picture, the voltage now jumps over 17 at high rpm. Also, the voltage at the fuse panel reads under 11 with the car off (perhaps confusing the regulator). See the chart below for measured voltages. I won’t be driving it with those high readings. Should I start with the regulator points calibration as detailed in other threads? Is the low voltage at the panel not significant? The regulator ground wire is good, but could the F wire be the problem? Thanks for looking

 

[SteveH]

the voltage at the fuse panel reads under 11 with the car off

Seems to indicate a huge quiescent draw, or that your battery is half dead. What is the voltage of your battery (disconnected from the vehicle)? Do you see a spark when you reconnect the battery? You can also insert a ammeter in series with your battery and see what your quiescent draw is.

Are all your fusible links good and major ground wires clean and secure?

Finally, you should be able to remove the cover on the voltage regulator and watch it operating (mechanically) while the engine is running.

 

[NW Oregon 4me]

the voltage at the fuse panel reads under 11 with the car off

Seems to indicate a huge quiescent draw, or that your battery is half dead. What is the voltage of your battery (disconnected from the vehicle)? Do you see a spark when you reconnect the battery? You can also insert a ammeter in series with your battery and see what your quiescent draw is.

Are all your fusible links good and major ground wires clean and secure?

Finally, you should be able to remove the cover on the voltage regulator and watch it operating (mechanically) while the engine is running.

I’ve had the battery checked and it’s good. There is no spark when the cables are connected. I will check the other items you mentioned next week and report back. Thanks for the suggestions.

 

[Rzeppa]

Are all your fusible links good and major ground wires clean and secure?

A stock 1971 FJ40 has no fusible links, and unless there is a modern audio or security system, no source of quiescent draws. HOWEVER, Steve's second point is spot on - I had a recent issue in my 1978 FJ45. Root cause was an intermittent (I hate intermittent stuff!) negative battery cable connection. It would either be fine or high resistance (read 1.2V at the fuse panel with the key on), I discovered it the old fashioned way - wiggling the cable by hand while observing voltages and stuff like headlights lit or not when they should have simply been lit. Replacing the negative battery cable completely solved the problem. A high impedance negative battery connection could definitely cause the regulator to put out more voltage than it should while the motor is running! On our old 40s, the negative battery connection is to the frame is subject to salt spray and corrosion inside the right wheel well, and can certainly be suspect!

 

[NW Oregon 4me]

A stock 1971 FJ40 has no fusible links, and unless there is a modern audio or security system, no source of quiescent draws. HOWEVER, Steve's second point is spot on - I had a recent issue in my 1978 FJ45. Root cause was an intermittent (I hate intermittent stuff!) negative battery cable connection. It would either be fine or high resistance (read 1.2V at the fuse panel with the key on), I discovered it the old fashioned way - wiggling the cable by hand while observing voltages and stuff like headlights lit or not when they should have simply been lit. Replacing the negative battery cable completely solved the problem. A high impedance negative battery connection could definitely cause the regulator to put out more voltage than it should while the motor is running! On our old 40s, the negative battery connection is to the frame is subject to salt spray and corrosion inside the right wheel well, and can certainly be suspect!

worth checking, thanks