Over Charging

[mvent]

Stumbled on a problem, 68 GTX Auto with a/c wiring appears stock. While checking battery voltage with engine off then running, it appears voltage at battery starts at about 12.6 engine off then on starts at 13.7 and just idling keeps increasing to 15.5+. Checked ignition post at VR and it's about 1 volt above battery volts. I do have about 1 volt drop at VR ignition side and alternator with key on not running. I understand with voltage drop at VR would cause to up the alternator output but gradually continue to rise? Grounds at VR are good and VR and ballast are new. Any ideas where to look?

 

[RJRENTON]

IMO....consider installing a "new style" regulator, the one that resembles the old unit, but contains trsnsistorized internals, that replaced the mechanical relay type......far more accurate and faster response time.....just a thought....
BOB RENTON

 

[mvent]

Bob thanks for that suggestion. In your experience is it correct to have 15.5 plus going into ignition side of VR? Also do you think the VR could be causing volts to gradually increase while idling? I thought if VR was not functioning properly it would go right to high volts. FWIW same volts at alternator as battery key off, with key on about 1 volt less at alternator and wire to ignition side of VR disconnected, when connected there is another .4 loss

 

[RJRENTON]

Bob thanks for that suggestion. In your experience is it correct to have 15.5 plus going into ignition side of VR? Also do you think the VR could be causing volts to gradually increase while idling? I thought if VR was not functioning properly it would go right to high volts. FWIW same volts at alternator as battery key off, with key on about 1 volt less at alternator and wire to ignition side of VR disconnected, when connected there is another .4 loss

The ignition side of the voltage regulator provides the reference signal, that the regulator uses to control the overall system voltage with or the how it adjusts the alternators rotating field voltage..and ultimately the alternators output. If you're talking about the origional type mechanical voltage regulator, a fault will cause two scenarios: maximum output or no output. In the origional voltage regulator, there is an internal "fuse type" connection that, if, the contacts stick, will open causing a no voltage connection. If the voltage regulator's internal operating coil fails, resulting in no control, the alternators output voltage will climb to the design maximum. It is possible to have a slight voltage loss, as you noted, due to terminal resistance somewhere in the system, although it might be difficult to pinpoint the exact location, but PROBABLY, it may be in the bulkhead connection. Just my opinion of course.
BOB RENTON

 

[mvent]

In checking today I removed leads to ballast resistor and put probe in wire going to ignition side of VR not connected and meter read within .05 volts at battery, plugged wire into VR, ballast still unplugged and loss .8 volts, plugged ballast in and loss another .4 volts for 1.2 total. These numbers are also at alternator stud. Should this be? I'm reading .06 ohms across ballast unplugged FWIW.

 

[mvent]

Forgot to mention this was done key in run position, not running.

 

[Darter6]

mvent, did you ever solve your problem ?

 

[mvent]

mvent, did you ever solve your problem ?

Maybe, replaced VR with transistor type with original looking case which was recommended here and now I'm steady at 14.5V. Still high IMO. Also added 8 gauge wire with fusible link from alternator to starter relay. Took car to Bill Atwood at Auto Service of Old Saybrook for tune up and Pertronix conversion on his recommendation. He also suggested I bring it back over winter for him to check out/replace under dash harness if need be. Great place by the way for people nearby, I drove over an hour to have them work on it.